Hi, I just logged on here and I've got a ton of questions and not really sure where to start.
About six months ago my partner and I bought an 'Off-grid solar cabin Kit' from Home Depot that included the Midnite Classic 150, plus six 300w solar panels and a couple of wires and breakers -- and that was it! We thought we were getting an easy and simple do-it-yourself kit but of course we had to figure out a lot, and we also had buy a LOT more stuff in order to complete the system.
Anyway, we just finally finished mounting and wiring the system and now we're trying to figure out how to set all the different settings. I watched the youtube videos posted by Midnite Solar and then referred to my battery spec sheet for guidance, but that still leaves me guessing as to how everything should ideally be set. There is still a fair amount I don't "get" about this controller but we do have it running right now and we have a decent load on it and everything seems fine. But -- the Classic's fan is running pretty much non stop which has me concerned. It is a fairly warm day today, about 75f. Anyway should I be concerned?
Here are my 'guesstimate' settings:
I have my EQ set to 28.8v. My absorb is also set at 28.8. Float is at 27.6 (all 4 batts are brand new)
Absorb time 2 hrs. EQ 1hr. 15 mins.
T-comp -5. mv (default) (I have no idea what this is about)
I have the intermittent EQ set to once every 59 days -- for 1 hour. (have no clue what this setting should be)
Rebulk is set at 25.5v
Charge output 96amps (default). Input 99 (default)
T-comp min: 26.4v max: 30 (default settings)
My system: 6 300w Renogy panels wired 3s2p
Midnite Classic 150 CC
4 AGM Renogy 12v 200 amp batteries wired 2s2p
Aims 3000w Inverter
I do not have the Whiz Bang Jr. I have a Renogy battery monitor instead.
I would welcome any input from any kind person who understands this better than me, which I'm sure is most everyone here!
Lisa
Welcome Lisa !
Yeah, sometimes that fan just likes to run when it is warm. The Classic will tend to heat itself up a bit also and when it is warm out, it heats up more. I would say that as long as the Fan goes off at ALL, it should be OK. If it stays on like ALL of the time, even at night when the Classic is "Resting", then something might be making it stick on. That can be remedied if that is the case but I expect things are actually OK there.
Your settings for Absorb and EQ are OK. Typically EQ or Equalize isn't all that necessary even. When those two voltage set-points are set the same, the EQ won't be any different than the Absorb cycles happening 2 hours at at time. But it won't hurt to have it set the way you do, every 59 days. Just playing with things like that should be good to kind of get to know the system or at least the menus in the Classic's display. OK, so far so good...
As for the Absorb voltage and time that you chose, 28.8V or so, that sounds about right... BUT the real settings should be specified by the battery manufacturer. And you also chose the typical correct value of -5mV per degree Celcius temp comp.
What that means is that the Absorb voltage (and Float voltage after the Absorb has done its 2 hours) will go DOWN by 5 thousandths of a volt for every cell in the batteries when the batteries temperature goes up one degree C. Lead Acid batteries usually are made up of 2V cells. That -5mV is for each one of those. You have a 24volt battery so you have 12 of those 2V cells. 5 mV times 12 is 0.060 volts per degree C total ( -60mV / degree C) so you won't see much if any change in Absorb voltage if those batteries voltages change by just 1 degree C. Maybe 0.1 volt ?
The reference temperature for the temperature compensation voltage is at 25 degrees C or around 77 degrees F. Did you plug in the battery temperature sensor and stick it on one of your batteries ? You can go to the TEMERATURE menu on the Classic remote control and see what the Classic thinks that voltage is. So if your batteries are at 30 degrees C (5 degrees different than 25C) then the charging voltage will go down by 0.06V times 5 = 0.3 volts.
When that happens, your Classic, instead of charging the batteries at 28.8V will be trying to charge them at 28.5 volts.
The opposite happens when the batteries are colder than 25 degrees C.
OK, enough for right now. Others will come on here as well. Yeah there is a LOT to learn but if you keep your batteries in good shape and the panels clear and hopefully the fan(s) are just because it's warm now, you should have a great system.
You may find out eventually that you need or want more batteries or solar panels but this is a good start ! And be careful not to use too much electricity and wear down the batteries too much each day so that they have a long life. Usually, 50% discharge is good.
If you find yourself discharging the batteries almost all the way most days, then you may need twice the battery capacity overall.
boB
What are the ratings on the panels ?
You could use the Midnite String Calculator to give you ( and us ) more info .
Just put the numbers from the back of one of your pv panels in here https://www.midnitesolar.com/sizingTool/
If you have the PV string voltage a lot higher than the charging voltage that will tend to make the fan run more as long as it is charging.
The Whizbang is well worth the investment - you will also need a shunt with it and not to hard to install in your system. With the Whizbang you will get a very close estimate of exactly what the SOC State of Charge of your batteries are and also be able to use Ending amps to terminate the Absorb and go to Float - it is better than just using hours . But you need to figure out the correct value for ending amps using some observation of your system at first.
But otherwise like Bob said most of your settings look okay - except check on battery temp compensation value - some batteries are -3mv instead of -5mv .
Also if you have Android phone get the Classic Monitoring App off of Google Play .
Larry
Hi boB and Larry, I really appreciate your help on this!
Firstly, no, the Classic's fan isn't on all the time, just maybe about 60 percent of the time when there's a load on it, and at night (when I don't have a load on the system) its totally quiet. With everything being new to me I'm sort of nervous about everything right now. There was also a sort of sulfur, electronic smell about the Classic on the first two days but I think that's dissipating now. The inverter makes a bit of a hissing sound when we first turn it on, so all these little things have our (hyper) attention and have been giving me a nervous stomach.
So as to the temp... My partner did hook up the blue temp sensor (long blue wire from the Classic to the battery bank) but he has it hanging between two of the batteries -- I think we read (somewhere) it's not necessary to adhere it to the battery. Should we stick it to the side of one of the batteries? And that said, I can't find where the temperature menu is! You said it's on the Classic "remote" control? Not sure what you're referring to. I looked for it in the Classic's main menu where everything else is, and couldn't find it. I probably should mention I don't have the Classic hooked up to my internet. I don't have a cell phone so I'm assuming I wouldn't be able to hook the system to my computer since it requires an APP. ??
"As for the Absorb voltage and time that you chose, 28.8V or so, that sounds about right... BUT the real settings should be specified by the battery manufacturer."
I'll attach my battery spec sheet and maybe that will clarify whether I've got this at a good setting or not. I could email Renogy but last time I did they took nearly a month to answer.
Larry, I'll go up on the roof tomorrow and get that number off one of the panels and take it to that link you gave. I think we're okay regarding the fans but I'll check on that anyway.
As to the Whiz Bang, unfortunately the Whiz Bang was one of the things not included in the kit. Gosh darn it. I didn't hear of the Whizbang till after I'd bought a Renogy batt monitor, which is a good quality monitor and cost about a hundred. It's hooked up and giving me very good readings but now I've learned that I can't calibrate the Endamps unless I have the Whiz? So, is this pretty important to be able to do? Actually at this point I have no idea what the Endamp function is. I read about it but it it was a little too technical for me to follow.
Anyway, fortunately so far we've been able to mount and wire up everything, plug stuff into it, and so far nothing ruined! As to the batteries, we'll probably never discharge them much at all. This is just a back up system for us that we wanted to have for when our PG&E shuts down -- which it's been doing a lot lately. We're just going to use it mostly during daylight hours to power a few things that I run during the day. Batts may never need to drop below 80%. But that raises the question of breaking the batteries in. I'm thinking perhaps I should make a point to drain them at least to 80% for about fifty times, so that they're broken in ?? Or perhaps more?? Wow, is this complicated or what???!!
Anyway, thanks again guys! I really appreciate your help soooooo much!
Lisa
Most AGM batteries have the same voltage setpoints . You don't want to equalize - in the most common sense of the term which is a controlled overcharge. But since you have the equalize voltage the same as the absorb you are okay - though I would just just disable equalize for an AGM battery .
If your battery supplier won't give you good info just look up AGM batteries for another battery supplier and you will learn the general characteristics and care of them.
Not sure if you wired the batteries or if they came prewired but with the parallel connection you want to take special care so the wiring is correct otherwise the charge discharge may favor one string over the other.
Look at this for more info
http://www.smartgauge.co.uk/batt_con.html
I am not familiar with the Renogy battery monitor. Do you know if there is a shunt in the system that it connects to ? The shunt would be the first thing that the battery negative terminal connects to if it was there - and all the other negative connections would be on the other side of it.
You should consider getting a router which wouldn't even need to be connected to the internet - any old router should work - to plug the Classic into. That way you could program and monitor using apps on computer or android phone or tablet. Makes life easier for sure.
Yes to all the fan sounds and noises controllers and inverters can make. Mine are not where I can hear them all the time so I don't take too much notice most of the time. It sounds like the fan on your Classic is working normally.
Yes there is usually a break in for new batteries to get them to their full capacity . Again look up AGM batteries on East Penn Deka or Rolls or some other battery company if you can't find the info from Renogy . Or here https://batteryuniversity.com/learn/article/absorbent_glass_mat_agm
I have to run but can answer more questions later.
Larry
Hi Lisa..,
If your Renogy PVs are Polycrystalline, then this is probably the spec for them:
file:///C:/Users/OMX/Documents/Renogy%20300-W%20Poly%20PV%20Spec.pdf
Couple of things. In an ideal world, if the above PVs are the ones in your system, the best PV string configuration would probably be three strings of two PVs. This will reduce the input voltage into the Classic. And, depending on the coldest temperatures at your location, on cold mornings/days, the input voltage might be so high that the Classic will shutoff, protecting itself. Restringing PVs can be a bit of a pain, AND, when there are PV strings of three or more, an added electrical box with circuit breakers needs to be added, for safety and debugging convenience. This would change the PV wiring, a tit. (not to rain on the Parade, too much).
Some research needs to be done to check the proper battery charge temperature compensation value. AGM batteries often use between about -3-4 mV per cell. Your setting of -5mV, is fine for now. Will try to confirm the exact desire of your batteries.
Do you know the coldest temperature for the location of your cabin? This would help to determine the maximum input voltage for your system, in cold WX.
Using the string calculator has been mentioned in this Thread, we could run that calculator for you, if you could confirm the PM model number, the coldest and warmest temperatures.
Welcome here, Lisa. Thanks for added info, Vic
Hi Vic, thanks so much for your answer. Really appreciate everyone's help.
We actually have the monocrystalline panels. We can't get the info from the backs of the panels, they're bolted to the roof. But I did get the specs from the Home Depot site and I'll attach them to this post. We tried to fill in that string calculator but were not able to figure out which numbers went where, as terms are different. Maybe someone can help with this...
Hi Lisa,
The Renogy 300W Mono PVs that you are using (60 Cells, vs 72 cells for the Poly PVs), have a lower operating voltage.
Forget what I had said about high operating voltage going into the Classic. You should never see any issue with high input voltages, even on the coldest day.
Strings of three PVs should be fine.
Will try to confirm the charge temperature compensation for your AGM batteries.
Later, thanks, Vic
Great Vic, that would be great to know.
Lisa
Hi Larry, here's a link to the battery monitor: https://www.renogy.com/500a-battery-monitor/
Yes it came with a shunt and that's attached on the neg side of the battery. The monitor is working and also has a temp sensor but I can't get a read out on temp from that either. Weird! I've got two battery temp sensors and my system doesn't want to tell me what the temp is! :'(
Anyway, I'm still sort of trying to understand why I have to get a Whizbang. It's going to be a hassle to fit it into our arrangement, so before I get it I want to know why I gotta have it. What if I reset the "absorb" time from two hours to one hour? Would that be a bad idea? As I said we're not going to be using the batteries much so if not having a Whizbang means they'll last a few days less I could live with that. Btw, the batteries are all wired properly and in fact all wired with 4/O cable.
I don't know what a router is. Will it let me see the temperature of my batteries??? :'(
More stuff.... I guess that's fine as long as the end result is, my life becomes simpler :'(
p.s. Sorry for all the crying!
Lisa, you do not "need" the Whizbang Junior. It is nice to have but you should be fine with what you have.
Maybe some time in the future you can add one because they are pretty inexpensive but no absolute need now.
The main thing is to make sure your batteries are getting charged. That's the object with all of this.
Sounds like you are well on your way to being energy independent
Bob, glad to hear you say that. We'd have to redo some of our set-up to fit the Whizbang in and we just don't feel like doing that at this point. We are ready for the fun part now (kicking back and letting the sun do all the work). There will be a fun part to this, yes??
Btw, it was cooler today in the Bay Area and the MC fan seemed to be kicking on less than yesterday, so I think we're good there.
Yessss!
Hi again Vic, you had asked: "Do you know the coldest temperature for the location of your cabin? This would help to determine the maximum input voltage for your system, in cold WX."
Actually, our system is set up to be a back-up system for our house. We live in the S.F bay area and the climate is pretty mild here. The battery bank is inside our house in a box in the laundry room. Our laundry room gets maybe down to 45 degrees F on the coldest day of the year. It's usually above 50 in there though, even during the winter. The room is probably in the 58 to 75 degree range 90 percent of the time. We'll get a few days (like maybe 5) in the summer where the room may get into the 80s.
Were you able to find out if I need my t-comp setting at -3 mv rather than -5 ?
Lisa
Do you have internet where your Classic is ?
The internet in your house is usually plugged into a wireless router . The router has ports in the back of it - you plug a cat5 internet cable from Classic into the router. Then you can use the Midnite Local Status app or Grahams Classic Monitoring app .
Larry
Larry, I do have a new modem that I think can also serve as a wireless network bridge. It has several Cat5 sockets in the back. This will require a long cable because the modem is two rooms over from where the Classic is.
So my partner said he'll be willing to run the wire under the house and we'll probably do that. Will one of these APPs provide the means for me to get ALL the Classic's info onto my Mac? (Or if not my Mac, my partner's PC?)
EDIT: I finally found the Battery Temp readout in the Classic's display menu. I just wasn't scrolling down the line far enough to find it. Wow I'm dumb! but this is a bit confusing. Temp was 20.6, btw.
Thanks again for the help,
Lisa
Really need to know your lowest seasonal outdoor temp...it is used for the 'string' calculator. Lowest temps are times of highest voltage from PV panels. Too high of voltage can damagea Classic or any other CC.
Quote from: Lisa234 on May 10, 2020, 03:24:25 AM
Larry, I do have a new modem that I think can also serve as a wireless network bridge. It has several Cat5 sockets in the back. This will require a long cable because the modem is two rooms over from where the Classic is.
So my partner said he'll be willing to run the wire under the house and we'll probably do that. Will one of these APPs provide the means for me to get ALL the Classic's info onto my Mac? (Or if not my Mac, my partner's PC?)
EDIT: I finally found the Battery Temp readout in the Classic's display menu. I just wasn't scrolling down the line far enough to find it. Wow I'm dumb! but this is a bit confusing. Temp was 20.6, btw.
Thanks again for the help,
Lisa
Not sure about Macs - I only know about monitoring on Windows and Android . Maybe on Macs but that is your own geek research to figure out . An inexpensive Android tablet or find an Android phone someone is not using or getting rid of - there are millions out there. You can hook up to wifi with an android without have to pay for any phone service and use it's apps.
Larry
Bee88man, our lowest seasonal outdoor temp is 40 F.
Thanks for your help.
Lisa
p.s. I'll attach the PV specs again:
Hi Lisa,
Two things;
1. here is the Temp Compensation value for charging your AGM batteries .
"The effect of temperature on cycle charge voltage: -4 mV / °C / Cell'.
So a change of -5 mV, to -4 mV is all that is needed.
2. Ran the Classic String Sizer, and the results are attached (used the default high temperature).
You are fine on the effect of cold temps on the Voc.
And, Beeman, these Renogy PVs are 60 Cell modules. It is almost impossible to fine any location on Earth that is too cold for strings of three PVs, with a Classic 150.
The String Sizer states that Lisa's Classic 150 would enter Hyper Voc at about -95 degrees F, FWIW.
Vic
Vic, thank you VERY much for running the string sizer for me and getting the info on the T-comp. I will adjust the setting accordingly. Glad to know my PVs are no threat to my Classic as long as another ice age doesn't befall us.
So anyway -- awesome! I feel like I have this thing fairly well figured out now which is pretty cool because four days ago I was like - I'm never gonna get this!
I have a couple more questions. I noticed yesterday in the manual it says the Absorb time should be "proportional" to the Bulk time -- though it does not say what exactly that 'proportion' should be. So I don't really want to be taking a wild guess on this. I'm also assuming the Bulk time varies depending on how much the batts are discharged - and so I don't know how to figure out the best setting for the Absorb time.
Also wondering if Absorb time should be manually re-adjusted depending on what's happening with the Bulk time from one day to the next.
(I'm assuming the Ending Amp function won't work for me since I don't have the Whizbang)
Yeah I don't know what that statement about proportional would mean either. Never timed the Bulk here.
Just leave your 1 to 2 hours absorb time - whatever you decided on using.
It is true that sometimes you won't need the full Absorb time or might need a bit more. That is why ending amps is better since it ends absorb depending on when the amps into the batteries start to level off and you have figured out by testing specific gravity ( if you have flooded lead acid ) or just observed the leveling off point . Then the Classic would terminate Absorb and go into Float . So lets say you have 2 hours absorb time but the ending amps setting comes along at 1.5 hours - then it is done with absorb .
But you can't really use ending amps without the Whizbang because you have to know exactly how many amps is going into the battery as opposed to how many amps the Classic is producing - some of which are going into battery and some are going into loads. You can set that up once on Classic to use the Whizbang amps and then it does it automatically.
I think you said you have a different monitor . If that shows just amps going into the battery you could observe it and figure out the ending amps setting . To do that you would set the ending amps a bit longer , then watch when it goes from Bulk to Absorb. The Classic at that point will hold the voltage steady at the Absorb setpoint ( or a bit higher or lower depending on the temp compensation if the batteries are hotter or colder) . So you would see it stay at Absorb voltage and the amps going into the battery will start to drop as it charges and the SOC goes up . There will be a point where the amps starts to taper off and hold steady for awhile without changing much. That would be the ending amps. When you get your Classic plugged into internet you can set it up on MyMidnite and see the history graphs and see the curve much easier there.
So if you did everything correctly you would see Classic get to ending amps point around the time SOC gets to 100% full. You other external meter might not be as good an SOC as the Classic and Whizbang unless it take battery temperature and also has an efficiency setting.
So with your other monitoring meter you might be able to use it to spot the ending amps point and then manually end Absorb on the Classic if you were around watching it. At least you could see close you have your Absorb time set and tweak that better to be more in line with regular usage there.
Hope that all made sense.
Go to the Midnite Knowledge base on their website because they have a lot more details on some of these things that are not in the manual.
Larry
Hi Lisa,
The ideal Absorb time, will depend on the Depth Of Discharge (DOD) of the previous battery discharge. This is one of the reasons that many of us use End Amps to end Absorb.
In early Classic Firmware, there was an option to have the Absorb time equal the Bulk time. Make certain that you have the latest copy of the Manual:
http://www.midnitesolar.com/pdfs/Classic_ClassicSL_Manual_10-001-1_REV_L.pdf
AND, what is the Classic Firmware that is in your Classic?
AGM batteries need a fairly long Absorb time, (especially with parallel battery strings), on occasion. This long time can help keep the battery strings well-balanced.
The inexpensive WbJr, and a Shunt would probably be a useful addition to your system (as noted previously):
https://www.solar-electric.com/midnite-solar-whiz-bang-jr-current-sense-module.html
Shunt:
https://www.solar-electric.com/mkb-500-50.html
There may be a proper Shunt in your system, if the system has an e-panel, or MNDC.
Sometimes, using the Mid Nite Shunt can be useful, as it has provisions for a busbar to be attached to one side of the shunt:
https://www.solar-electric.com/midnite-solar-shunt.html
AGM batteries are a good solution for many systems, but, it is more difficult to determine the proper Absorb time, about the only method of determining actual SOC, is from the resting voltage, or from Ending Amps. On the systems here, using Flooded Lead Acid (FLA) batteries, the proper EA varies (at least somewhat), depending on the DOD of the battery.
There is a trick, that can be used on 12 or 24 V systems with two battery strings. This is to use a battery switch (a string 1, 2, or Both switch). This can allow one to separate the two battery strings, over night. The disconnected string Rests overnight. The Resting battery voltage of that string is measured in the morning. This voltage (when temp compensated), is a very good indication of the actual SOC of that string. The following day, the other string can be similarly Rested to check its SOC.
A possible switch:
https://www.solar-electric.com/basw1300amp.html
More later, FWIW, Vic
I think getting the Whizbang might be the easier way to go than getting a switch. But this will require my partner to go back to work re-arranging our set up. Wish the WBjr had come with the kit.
Anyway, I do have one other idea or something that will get us by for awhile. What if I turn all the loads off when its bulking and put the End Amps on 6amps (correct setting for my 400 AH system, yes?) I could be sure to get a nice full charge and, also, see how long it takes for Absorb to switch to float absent a load. I could note that time and then maybe do some math, figuring in the difference there might be with the loads on. I'll be putting the same loads on it every day, which is 450 watts.
I didn't update my manual with any new firmware. I'll get on that when I have a chance.
Anyway, thanks Bob and Larry really appreciate your help. Tell me what you think of my idea for using the Ending Amp function...
Lisa
Hey guys, attached is a picture of our shunt that goes with our Renogy battery monitor. Would that work with the WBjr?
Specs:
Universal Battery Monitor- Voltage range 10V-120V and up to 500A
Accurate Battery SOC%
And here is a sample picture of our batt monitor. (This is NOT actually our monitor, just the pic of it from the internet.) I don't think it's able to tell me what amps are going into the battery...unless I'm missing it ?
(Also, I don't know what that number 8:44 represents. Maybe someone could clue me in ? :)
Lisa
Vic, yes, I must have the old manual because the wording regarding Absorb has indeed changed. They took the part out about "proportional". Thank you for sending me that link.
Anyway, I just got some good news from Renogy. They told me that I do not have to break in my batteries and its a simple matter of the less used the longer they'll last - period. Well that should make things easy for me! Absorb time can be very short when my batteries are barely discharged. Maybe they'll last my whole life!
Quote from: Lisa234 on May 12, 2020, 12:27:32 PM
I think getting the Whizbang sounds like a better idea than getting a switch. But this will require my partner to go back to work re-arranging our set up because as it's arranged there's no room for the WB. Wish the WBjr had come with the kit.
Anyway, I do have one other idea or something that will get us by for awhile. What if I turn all the loads off when its bulking and put the End Amps on 6amps (correct setting for my 400 AH system, yes?) I could be sure to get a nice full charge and, also, see how long it takes for Absorb to switch to float absent a load. I could note that time and then maybe do some math, figuring in the difference there might be with the loads on. I'll be putting the same loads on it every day, which is 400 watts.
I didn't update my manual with any new firmware. I'll look up what version I have as soon as I have a chance. We got this "kit" about 7 months ago.
Anyway, thanks Bob and Larry really appreciate your help. Tell me what you think of my idea for using the Ending Amp function...
Lisa
Hi Lisa,
Before the introduction of the WbJr, for the Classics, and also, when using the Outback Power MX-60 CC, we used CC (total) output current (I call this: CC EA) and EA settings to end Absorb.
This works a bit better when the system uses Flooded batteries, where the actual SG readings can be taken by sampling the actual electrolyte in each cell. WIth sealed batteries, like AGMs, this is not possible.
For systems with fairly repeatable loads on the inverter, CC EA, as you described, should work fine. Particularly, when one realizes that, the loads on the inverter only really matter around the time that the Absorb should be ending. Even with cyclic loads, cycling on/off near Absorb end, CC EA can still work well. There is just the open question of how one determines weather a particular EA is really allowing the batteries to be fully recharged.
That Renogy Shunt may not be a 50 mV 500 A type. There is probably a Scale Factor setting that could possibly be made in the Classic, but I do not know how to set it, if it exists.
If you have the manual for the Renogy batt monitor, each reading of the display should be defined.
Later, it looks like you have a good handle on your system, and you have done quite well in getting it installed well, and are a quick study on the settings for the Classic. Good Work !! Vic
Thanks Vic, nice of you to say that. So I just did the Absorb cycle with all my loads removed and Ending Amps set on 7. I think that was a good idea. Absorb took 50 minutes and I have a feeling it's well charged -- the amps were coming down very slowly right at the end.
So I'm thinking, I'll probably just keep the Ending Amp ON and switch my inverter & load on after it gets into Float.
This would be a really easy routine for me. We'll probably get the WBjr at some future time, though.
Hi Lisa,
When watching the Ending Amps, when trying to determine a good EA setting, IMO, would keep watching the current, and when you finally believe that this current will never, EVER, go any lower. This is the approximate proper value (at least for that DOD of the battery).
Would also suggest, that about every two, weeks, or so, that you increase the Absorb time by about 25 - 50 percent, to try to make sure that the batteries are not being chronically under charged. With parallel strings of AGMs, one string can hog more charge current. This can result in the other string getting undercharged, chronically, and can lead to battery damage. During a long Absorb, the current hogging battery gets fully charged first. Long Absorb can allow a lagging string to get its chance at a full charge.
It is conceivable, that one could use the Auto EQ function, to do this periodic long Absorb. Just a question of just how long to make the time setting on this.
The old saying, is, that it is better to overcharge batteries, a bit, than to under charge them.
On the Renogy batt monitor, the current shown, simply must be the battery charge/discharge current, as the monitor has no way of knowing any other current. In that sample pic you posted, guess that that dash, to the left of the displayed current, it the Polarity of the current. Probably has no + for charge current, and just the dash, for discharge current (GUESSING).
The Shunt for the batt monitor IS a 500 A unit. SO, their is reasonable probability that this shunt is 50 mV, which is a very common value. If so, this would work with the WbJr.
There is a way to change the Scale Factor, to use a Shunt that has a different voltage output for a given battery current. This is a bit technical, but is discussed in the following Thread:
http://midniteftp.com/forum/index.php?topic=1413.msg12226#msg12226
Anyway, all FWIW Guessing done for now, VIc
Yes, Vic, I'll definitely experiment with lower Ending Amp settings and check the flow. I'll also ask Renogy about EQing, see what their view is. Will ask them about the Mvs on the shunt too (I don't know what happened to my paperwork on that Monitor/shunt). It sure would be great news if we can use our shunt with the WBjr.
Anyway, thanks again for all your help!!!!
Hi Lisa,
Just to be clear, AGM batteries are NOT EQed in the traditional sense. Generally, they cannot tolerate voltages above the manufacturer's spec for Absorb.
But, some AGM battery manufacturers consider an extended-time Absorb to perform an equalizing function.
The Manual for the Renogy battery monitor, IS on-line. But, it does not specify the shunt's voltage range. AND, it does not seem to define just what is the apparent clock function on the display.
FWIW, Vic
Okay thanks Vic, good to know.
Interestingly, I set the End Amps down to 5.5 for today's cycle and the Absorb cycle came and went so fast I didn't even get to watch it happen. Must have been less than 15 min. That surprised me since yesterday's took almost an hour - though the batteries were slightly more discharged yesterday.
Quote from: Lisa234 on May 13, 2020, 11:19:58 AM
Okay thanks Vic, good to know.
Interestingly, I set the End Amps down to 5.5 for today's cycle and the Absorb cycle came and went so fast I didn't even get to watch it happen. Must have been less than 15 min. That surprised me since yesterday's took almost an hour - though the batteries were slightly more discharged yesterday.
When your batteries aren't discharged very much and you are putting lots of amps in you will probably see it just fill up and go to float fast.
I think I would run the batteries down to at least 50% full a few times if they are new just to make sure they are working properly.
The AGM batteries are all similar - read that link on AGM's from battery university if you didn't already and also read AGM info from East Penn Deka or Rolls just to compare details.
Larry
Thanks Larry. I think my batteries are probably fine, but I don't know about my monitor. Today for instance it was showing my battery bank sinking down to 94% even though I only had a small load on the system and it's a sunny day. It also showed the amp hours down from 400 to like 386. So I unplugged my laptop from the system, and the reading on the monitor instantly popped up to a 100% and 400ah. I plugged the computer back into the system and the monitor still showed 100% and 400ah.
Is this normal for a battery monitor to do?
Quote from: Lisa234 on May 13, 2020, 05:54:26 PM
Thanks Larry. I think my batteries are probably fine, but I don't know about my monitor. Today for instance it was showing my battery bank sinking down to 94% even though I only had a small load on the system and it's a sunny day. It also showed the amp hours down from 400 to like 386. So I unplugged my laptop from the system, and the reading on the monitor instantly popped up to a 100% and 400ah. I plugged the computer back into the system and the monitor still showed 100% and 400ah.
Is this normal for a battery monitor to do?
Save up your pennies to get a Whizbang . Might as well get the shunt that it will fit on too - unless you want to figure out if that one you have will work or not . The mv rating of it should be stamped on the side of the shunt. Then you would want to measure the two inner screws to see if the Whizbang would mount on it ( and the thread size and pitch) . If it was me I would just replace that shunt with the good Deltec shunt.
Larry
So the problem isn't with the cost of the WBjr, the problem is with our set up. If you look at this picture you can see a copper bar at the negative post of the Inverter breaker. My partner got that bar and shaped it to fit around the breaker and the shunt is mounted to it on the other side. You can can see the red wire that goes to it. It's a tight fit and we obviously can't see any numbers that might be on it. Now, if we want to get the WBjr and its shunt we'd have to take everything apart and redo all of it & maybe get a different box. So that's why I'm kind of inclined right now to try and live with the monitor I've got* for awhile at least. I also don't want to go out to get new stuff during lockdown.
*junk?
I was able to catch my system's Absorb time today: 35 seconds total.
I had my Ending Amps set at 6. All loads were off, inverter off. Amps were already around 2 when the MC flipped into Absorb.
So I'm assuming this is all good and my batteries are super charged ??
I just got this email from Renogy regarding my shunt:
Hi Lisa,
Thank you for contacting Renogy support.
Yes our battery monitor has a 500amp / 50mv shunt.
--------
So this is good news! We're going to go ahead and order the WBjr and since we can use the shunt we have, we can keep our set up as is. The Renogy monitor has been totally malfunctioning so I'll be really happy to replace it!
So hopefully with the WBjr I'll be able to figure out how much available power there is in my PV array at any given time of day..?
Also, I think Vic asked me which firmware I have. I have no idea. How would I find that out? And, is it essential for me to update?
Hi Lisa,
Great news, that your existing shunt will be compatible with the WbJr.
Using the MNGP Display panel on the Classic, from the main status page, press the small round button on the left about 6 - 7 times. This should bring you to the page that gives the Classic, MNGP and Network Firmware version numbers.
If you were able to run the Local App on your Windoze computer, the Firmware versions are listed there, as well.
Thanks for the update, Vic
You should deep cycle those batteries a few times and make sure they are working properly.
It won't hurt them.
There should be a date code stamped in the case on your AGM batteries. It wouldn't hurt to see how old they are.
If you are using any appreciable amount of power at night they should be in Absorb for longer than 35 seconds .
Larry
Hi Larry thanks for that (and thanks also to Vic for his post 2 days ago). Yeah I was figuring on giving the bank an extra long charge about once every 10 days. I'm hardly discharging my batteries at all. I have about 450 watts of appliances in my load and we have those things on two-pole toggle switches that give us the ability to manually (and seamlessly) switch them over from our city grid to the PVs when the sun is out, and flip them back off when the sun starts going down. That's sort of an unusual set up I know but this is, as I'd said earlier, really just a back up system for us in the event of a Zombie Apocalypse. ;D Anyway, I turn the inverter off at night and don't turn it back on till the sun is on the PVs. So, my batteries remain very charged and that's why there's almost no absorb time even though my Ending Amps are now set at 4. But I'm thinking I'll give it a 20-30 minute absorb charge by way of the 'time set' option every 10 days. Do you think that sounds reasonable? Or do you think I should go for an hour?
FWIW, I did ask a person at Renogy if I should discharge my batteries down, say 20 or 25% (ie down to 75% full) occasionally just to keep them healthy and he said no. With my AGM batteries he said the less use, the better.
Anyway, I will be getting my WBjr on Monday (yeay!!) and we'll get that hooked up right away. I sure hope it gives really accurate moment to moment readings on batt discharge because the Renogy monitor does not!
There is some truth to the fact that the less deep that you discharge your batteries the longer they will last.
But the other thing that is very true is that if it isn't tested you don't know if it works. So you should run your loads off your batteries down to 50 % once just to make sure they work and hold their voltage. You could have a bad battery and never even know it if you don't test it . Plus I still think that it is good to break in new batteries with some deep discharges in the beginning - to test their capacity and some batteries won't get their full capacity until you do.
I worked maintenance and we tested things like the generators, transfer switches, fire pumps, etc once a month - to make sure they all work . Sometimes you find problems and the best time to find the problem is when you don't need it as a real backup.
The thing with AGM batteries - some of them anyway - is they can get out of balance when they are always in float . At least that is what happened to some of the ones that were backup for our fire alarm systems. We replaced a lot of AGM batteries after only one year of use and they were in float all the time - of course there may have been other contributing factors such as charging systems, age of batteries and care prior to installation, etc. Did you ever look at the date code on your batteries and see how far from manufacture they were before you got them ?
Good to hear your Whizbang is on the way. Keep in mind that it is designed with screws and holes that fit in a standard Deltec shunt - and if your shunt has different dimension between holes or different pitch on screws then you will have to connect it not on the shunt but make some wires that go to it .
Larry
Larry, there's no date stamp on the batteries. I emailed Renogy after I got them and they said the batteries were new judging by the charge they held (which I found with my multimeter) ranged from 12.88 to 12.92v. Yeah, it seemed sort of questionable that there was no date.
Anyway, I did take the batteries down to 80% full last week and everything seemed okay. But given your experience with batteries i'll take the bank down 50%, and see what happens. I've been testing the voltage on the batts with my meter every morning after their overnight rest and this morning they were all within .01v of each other. I do notice they all like to drift from their float level which is 27.4 to pretty much exactly the level they were at when I first got them which is a volt and a half lower.
Yes, my partner is going to use wires to make our shunt work with the WBjr. He worked as a maintenance mechanic for a grain mill many years ago, so he knows how to wire stuff but he doesn't know much about these types of batteries. He's leaving this part of it up to me :'( I'd love to be able to avoid ruining them prematurely!
I have seen AGM batteries show a very good voltage but when they were under load the voltage would take a big dive.
Your batteries are probably good - but is a good idea to test them to make sure they are up to their specs. Usually battery manufacturers show a graph that will show what the voltage should be under a certain amp load. Sometimes the date code can be really hard to spot - usually small print stamped in along the top or along the side somewhere ( often up near top) Renology almost certainly just buys and rebrands batteries so it might even be hidden under a sticker if they put on a sticker. But no problem if they work they work. Just depends if you want to test to the specs , but if Renology doesn't publish specs then can't do that.
here is info on East Penn Deka AGM - in general you should expect your AGM to share similar specs if they are of good quality.
The graphs on first page will give you some insight into AGM characteristics . There is one that shows AGM Cycle Life vs Depth of Discharge
https://www.mkbattery.com/application/files/5515/3815/3319/AGM_Brochure.pdf
https://www.eastpennmanufacturing.com/wp-content/uploads/Renewable-Energy-Charging-Parameters-1913.pdf
Larry
Thanks for that info Larry. Really appreciate your help!
My partner and I got our WhizBang Jr. installed yesterday but we ran into problems. It had to do with a wiring issue. initially my partner had the controller and the inverter sharing the same negative cable, but last week we ran across a mention in the manual saying wiring in that manner could cause an issue, so, he changed it by running the wire directly to the battery bank, but in re wiring it he inadvertently bypassed the shunt. That was why my Renogy monitor stopped working last week! So it wasn't a piece of junk afterall, it was operator error! Anyway so when we put the WBjr in yesterday it was also not working -- it was reading the juice that was flowing to the load as juice coming from the batteries when it was not. So we were seeing our Stutus screen reading out a negative flow from the batteries like MINUS 15 amps when the battery was actually at a 100% and in Float. So the battery SOC in the WBjr Status window started sliding down fast and the AHs as well. So we knew the problem had to be the wiring and my partner finally realized the WBjr was only reading amps going out to the inverter and logging that as a draw from the battery. I guess!! Anyway, last night he rewired it and now it's measuring the flow to and from the battery and everything seems okay. This morning it bulked as usual and went into absorb briefly via End Amps (as usual) and when it went into Float it simultaneously returned to 100% SOC. Still a problem though: the AHs did not return to 400AH (my battery capacity) but stayed down were it was from the day before at 379AH (that was what it had run down to with the WBjr wired up wrong but I expected that to go back up to 400AH now that the wiring's right). Interestingly, the AHs have been creeping up all day, about 1 ah per hour and now it's up to 391. Also, the battery, after holding at 100% for several hours slipped down to 99% SoC at about 2pm but the voltage is still at the Float Set point (27.4) so that seems weird to me. How can 27.4v be 100% and then be 99%??
In the status screen the Amp draw reads out about .3 though it wavers up and down a little, continuously and sometimes the MINUS sign appears for a brief moment.
Anyway, I read through old postings on this forum to see if there was a way I could re-set the AHs and someone said going to the Amp hours screen and pressing left arrow plus enter and holding them down would reset the AHs but I tried that and it didn't do anything. I tried it on several screens and it didn't work. Anyway, I'm pretty confused by this situation. Perhaps I should do the Full out system reboot? I have noticed that one of my screens is showing I've drawn 45 AHs from my batteries but that's not so and I'd like to correct that but it seems to be permanent.
Also, I'm not sure what some of my settings should be. I have my "efficiency" setting on the default at 94%. Hope that's right.
Anyway, sorry for the long post. I hope someone can help me out a little!
Lisa ,
You have a lot packed in there so I will try to answer some of your questions.
Yes the way the shunt should be installed is - the battery negative cable goes to one side of the shunt and every other negative on the system will be on the other side of the shunt. This is easy to check - only one connection on one side going to battery - no other negative connections on the battery side ( or direct to the battery ).
If you haven't done it you need to set the shunt setting to external . And then set AHs capacity and battery efficiency in the Whizbang setup screen. You will probably want to start with something like 90% efficient and you can tweak that later to get more accurate. I know Vic puts in a much lower efficiency for flooded lead acid but you have AGM so is probably higher. 94% is probably okay too. The way I think about it - I would rather err on the side that my batteries are fully charged than not so would rather have the efficiency set a bit lower than higher. As the batteries age you can lower the efficiency over the years to reflect that. Keep in mind that the SOC and the AH counting are not changing any of your charging setpoints - they are only a view of battery capacity .
There is a setting in Tweaks for Whizbang reset - forget what the default is but it will reset the SOC to 100% when Classic goes to float .
I forget where to reset the total AH. Have you read the Midnite knowledge base ? There are a lot of FAQ questions answered there. Also there are a lot of videos on Midnites youtube page that explain a lot of things.
As far as the AH not going back to the total capacity - that can be related to some other factors like not having the efficiency set correctly. The SOC is a good indication of what is going on with the batteries but you need to get it set up correctly by some system observation. Everything is a bit of a guessing game with what is going on in the batteries but the Whizbang and SOC is probably the best guess you will find.
The amp reading is not directly related to the AH capacity history and counting - I mean if you see some current usage or charging that is real time . You have to consider that you have some loads on the system - inverters draw if on but no loads, the Classic itself draws some power to run it, and whatever other loads you might have on .
Keep in mind too that the batteries SOC capacity gets adjusted by the battery temperature.
Larry
Really appreciate it Larry-- Yes I read your post aloud to him and he says he's got the shunt wired correctly now (let's hope so!!). As to the WBjr reset, I set that to "Yes" but it's a daily reset and doesn't reset the complete history. I'd like to get that -45 AHs expunged off my record, but on the other hand I guess it's not a big deal.
As to setting the shunt to external, not sure. I did select the shunt in the "advanced window". And the shunt and WBjr seemed to be fully engaged to the Classic. Not sure if that's what you're referring to.
The instructions that came with the WBjr said to refer to the main Manual for total reset but I looked there and couldn't find help on that. Anyway, funny thing-- the AHs seem to be finding their
way back to the 400AH level. They crept up all day and are now reading 395. I did set my efficiency down to where you suggested (just now) so maybe that will help. It might also help keep the battery SoC reading at 100%. I guess we'll see. Today was pretty warm here -- the batteries got up to 23.7 C . I would have no idea how that might affect the readings though, tbh.
I'm not sure if I've seen the Knowledge base. I will find it and read up.
Thanks VERY much for your input Larry!
Lisa
here is the knowledge base
No exact direct link to it - not sure why not but you will see it listed here
http://www.midnitehelp.com/
Midnite Solar youtube videos
https://www.youtube.com/user/MidNiteSolar/videos
Larry
Hi Lisa,
The Remaining Ah reading will be reduced from 100% (400 Ah), if the battery temperature is below the Reference temperature (usually 25 degrees C).
Here is how to Reset Net Ah:
The Net Ah and SOC can be reset Manually from the Classic MNGP front panel. Push the left small round button on the display (IIRC, this is the Status Button), about four times (from the Main Status page) -- this takes you to the WbJr Status screen. Press the Left Soft button (square one, upper left). This takes you to the Net Ah screen. Hold down the left Arrow button, while pressing Enter. (it may take a second or three, but,) This should reset the Net Ah to 0, and the SOC to 100%.
Also, long ago, IIRC, you mentioned that the Classic Battery Temp Sensor (BTS), was suspended near a battery (or similar). If this BTS has not been attached to a battery, please do so now. Normally the BTS would be stuck about midway down the side of one battery, in the inside center of the battery bank. Having the Classic able to do its best job possible in measuring the actual battery temperature, is important, especially with AGM batteries (which are very sensitive to accurate charge voltages).
Later, Vic
Hi Vic, thanks for weighing in!
Yes I do have the reference temp set at 25 deg C. Sensor is right on the battery now. So, the charge cycle happened about an hour ago and AHs were at 385. Seems awfully low. But as with yesterday the number seems to be on it's way up. Now it's 386. Yesterday it got to 395 by the afternoon, and the battery was at 23.7 C. (I have that temp compensation setting at 1%).
As to clearing the daily net amps, yes, I was able to do that but the problem was, I couldn't clear the negative AH and positive AH history. Well, until just a few minutes ago! After a lot of searching I finally discovered how!
To reset the entire cumulative amp hour history you have to go to the Logs window, press enter and when the logs window shows up press ENTER again and make sure you press it hard. A "Clear Log: UP/DOWN chooses" selection will appear and then you have to press the UP arrow to bring each selection out one after the other. For me the UP arrow button had to be pressed repeatedly till I got to selection 7 which read: Clear entire NEG AMP history. And then I pressed enter. And that did it!!! ;D
(Anyway, I wanted to write that out so that someone searching this topic could see it.)
So everything seems okay now except the AHs reading seems low to me. My Renogy monitor always showed the battery bank at 400 AHs when Float was reached in the morning. So.... Not that I don't like the WBjr waaaaay better... I definitely do, but I need to understand it.
Hi Lisa, OK on the Reset that you wanted to do …
Forget if the Renogy monitor had a BTS, but if it did not, then this could be the difference twix the Classic and it.
With AGMs, (because the actual SGs cannot be directly measured), SOC readings can be more important than for Flooded batteries.
BUT, any SOC readings on any practical monitoring device are just approximations, as there are SO many variables that our monitors cannot/do not take into account. The largest of which is the Peukert effect. This is where the amount of Remaining Ah, and therefore SOC will vary, based on the (current) Rate at which the battery was discharged, on average. There are many other factors, SO, IMO, SOC readings may not be too accurate.
Have asked Renogy several additional Tech questions, to which they have not yet responded. One of which was for info on Resting battery voltage vs SOC, and temperature. This could help you better-determine the actual SOC of your batteries.
Later, sounds like you continue to get your system dialed-in. Good work !!
Vic
Thanks Vic. What about checking the individual batteries with a multimeter? Do you guys ever do that and can that be useful? I do check mine all the time, although, I've read that the only proper time to do so is after the batteries have been at rest for several hours. But I don't see why checking them directly anytime you like isn't helpful...?
Oh, btw, I think I do have the latest firmware, updated 2/06/18.
Anyway, happy memorial day everyone. Hope you're all seeing incredible weather as we are in the bay area today.
Lisa
Hi Lisa,
It is good that you are checking individual battery voltages.
With parallel strings, things can get a bit more complex. As an example, if one string has a higher SOC than the other (which would mean that the higher SOC string would have a higher string voltage, were it not for the other string), so the higher SOC string begins charging the lower SOC string, when there is no other charge source. This will reach equilibrium over time. A long Absorb time, on occasion, can help bring each string, and each battery into closer balance. This is what some AGM manufacturers call an EQ charge on this type of battery.
When trying to Rest a battery to determine its SOC, a customary Rest period is about 12 hours. And in systems with parallel battery strings, one would really want to separate the connection that parallels each string. Early in this Thread, that was where the suggestion of possibly having a battery switch that would allow separating strings, resting one to determine its SOC, then, resting the other within a day or so. This would allow determining the actual SOC of each string, and each battery in a string. This would require data from Renogy for the battery voltage vs SOC, and, ideally the temperature compensation factor of this Resting voltage ...
Your Ah Efficiency setting of 94%, is probably a good place to start for AGM batteries, which are considerably more efficient for charging than are Flooded batteries.
Since your system is for Grid backup, and it appears that you are not discharging the batteries very deeply, that you might be able to avoid recharging the batteries every day. The Classic has the ability to Skip Days, between full recharges.
Some backup systems with AGMs spend almost all of their time at Float voltage.
For best results, you would probably want to consult Renogy, about just what they recommend for battery charging, given the way that you are using them.
We are located in San Joaquin County, at about 3,000 Ft, nominal elevation. It will get warm in the next few days, but, we have had a very nice Spring, this year.
FWIW, Enjoy the WX, Vic
Okay good news! So this issue with the Battery AHs reading much too low was basically what Vic had suggested (I think Larry had also suggested it), a battery temp issue. Vic you had asked me if my sensor was adhered to the side of the battery and I said that it was stuck onto the battery* but actually it was being pinned down by one of the cables to the top of a battery. So this afternoon, when I went to actually tape it on properly I noted that the AHs were still not quite at 400. When I took hold of the sensor, just holding it in my hand for a couple of seconds caused the AH Status display to go instantly to 415 AHs! Wow. So I guess I must possess super powers?
Ha ha, so I taped it nice and snug with gaffers tape to the side of one of the batteries and in about 2 minutes the Status window read ~~ 400 AHs. ~~~ ;D ;D ;D
What a surprise, operator error strikes again... :o
Hi Lisa,
Thanks for the update. Great that you moved the BTS, and that things now, are a bit more predictable.
Am still awaiting info from Renogy, regarding rested battery voltage vs SOC … been a week, but hope that they will provide this info.
Have fun, keep cool, Thanks, Vic
Thanks Vic. I thought about what you said regarding daily re-charging and I agree that in my case re-charging every day is probably excessive. I think I'll set it to skip 3 days -- I've had End Amps set on 4 and Absorb was only coming on for about 2 seconds. Last night I set it to skip today and it's been Floating with a nice load on it at 100% SoC all day. Everything seems to be perfect perfect freaking perfect now!
Wow, when I first came onto this forum 18 days ago I didn't have any clue how the MC worked. I wasn't even sure what it was, ha ha. I've learned A LOT!
Lisa
Hi Lisa,
Renogy Tech did send the curves of SOC vs AGM battery cell voltage. Seems to lack the definition of the rest period, but probably was a 6 hour or more rest. See attachment. Of course just multiply by the 12 Cells that you have in your 24 V battery bank.
Have seen this exact graph for AGMs, but it was from another battery manufacturer. This graph was not on the datasheet that was downloaded from the Renogy site (even though, their e-mail stated that it WAS in that data sheet …), but assume that it is correct for your batteries.
If your batteries were fully-rested, when you measured your morning voltages, would guess that at that time your batteries were about 95-ish percent of full-charge.
Later, Vic
I don't trust voltages to show SOC for AGM's Vic - at least smaller ones. I have seen them have good voltage but take a big dive as soon as load is on them. The more accurate way to test them would be for how many battery manufacters publish cell voltages for certain loads.
Just reading the cell voltage at rest won't do it in my experience.
Larry
Vic thanks very much for going to the trouble of getting that info. Unless I'm missing something it seems to me everything's perfectly fine with my batteries. In the morning while still at rest (and after being in rest for 8 hours) they're each at 12.90v. Which would be 95% full, yes? On the "skip the charge day" they all bulk up to float 'set point' pretty quickly after the sun comes up. My float set point is 27.3v. Soc reading wavers from 100% to 99% all day. (I have my Frige and three computers on it most the day) So, 27.3v per string is really not 100% if I'm correctly recalling what i've read about the AGM batteries so it sort of seems right to me that SoC wavers from 100 to 99%.
Larry, thanks for your input, really appreciate it. I just asked my BF how one tests batteries with a load and he said we'd need a load tester and said we'll get one eventually but (in his opinion) these are new batteries and we're not putting much load on them so they really don't need testing now. Not to take away from your point but just saying perhaps I don't need to test with load for awhile. ??
Anyway, I get the feeling people who have had these systems awhile have learned to be very cautious (and perhaps mistrusting) about their batteries. I was on the Outback board first before I came here and a few people told me there that I would almost CERTAINLY ruin my first battery bank. Yikes - I read that and felt determined not to be one of those. Do you guys find that a lot of these batteries are sold in substandard condition? Or is this more about batteries not being properly cared for -- because batteries require so much attention ?
Lisa,
Newb here as well. Most of the solar forums tell folks they will ruin their first bank so get cheap batteries so the learning experience is not so expensive. I would counter with, "If you have a good balanced system you are not going to ruin your first bank." When we first put in our solar system (Rev 1) I started the banks life off with it being probably slightly undercharged for the first couple of months. As I read more and started learning more I re-wired things to better take advantage of the 'economy" 40 A MPPT controller. After about 4 months I had stuff pretty much dialed in and everything was fine in battery land. I ran this 300 AH bank (6 12V 100 AH AGM wired series parallel) for around two years and it was still going strong.
Last summer we installed solar system (Rev 2) which I wanted to take care of future needs and be able to run AC when it got hot. I wound up with 9 310W Mission Solar panels and a Classic 200SL feeding the original battery bank. This spring I upgraded to a considerably larger LiFePO4 battery bank and moved the AGM bank out to the shop/barn to run lights, etc., and the batteries are still fine. This is at our cabin which is 100% off-grid.
If I haven't put you to sleep yet I'll close with saying that if you feed your batteries what they need and take care of them you won't ruin them whether you are a newb or not!
Quote from: Lisa234 on May 29, 2020, 05:35:55 PM
Vic thanks very much for going to the trouble of getting that info. Unless I'm missing something it seems to me everything's perfectly fine with my batteries. In the morning while still at rest (and after being in rest for 8 hours) they're each at 12.90v. Which would be 95% full, yes? On the "skip the charge day" they all bulk up to float 'set point' pretty quickly after the sun comes up. My float set point is 27.3v. Soc reading wavers from 100% to 99% all day. (I have my Frige and three computers on it most the day) So, 27.3v per string is really not 100% if I'm correctly recalling what i've read about the AGM batteries so it sort of seems right to me that SoC wavers from 100 to 99%.
Larry, thanks for your input, really appreciate it. I just asked my BF how one tests batteries with a load and he said we'd need a load tester and said we'll get one eventually but (in his opinion) these are new batteries and we're not putting much load on them so they really don't need testing now. Not to take away from your point but just saying perhaps I don't need to test with load for awhile. ??
Anyway, I get the feeling people who have had these systems awhile have learned to be very cautious (and perhaps mistrusting) about their batteries. I was on the Outback board first before I came here and a few people told me there that I would almost CERTAINLY ruin my first battery bank. Yikes - I read that and felt determined not to be one of those. Do you guys find that a lot of these batteries are sold in substandard condition? Or is this more about batteries not being properly cared for -- because batteries require so much attention ?
You don't need an additional load tester. Just turn on all the loads you have and plug in some more . See how much current you are drawing and what the voltage drops to. Ideally you would have some large fixed resistance loads to test with - like space heaters which are 1200 watts and made to dissipate the heat they generate. Kind of depends how much you can plug into your inverter.
Larry
Quote from: ClassicCrazy on May 28, 2020, 10:23:42 PM
I don't trust voltages to show SOC for AGM's Vic - at least smaller ones. I have seen them have good voltage but take a big dive as soon as load is on them. The more accurate way to test them would be for how many battery manufacters publish cell voltages for certain loads.
Just reading the cell voltage at rest won't do it in my experience.
Larry
Hi Larry,
Thanks for chiming-in.
Given that Lisa's AGMs appear to be young, seems that they are probably not suffering from the most common causes of batteries having good resting terminal voltages, but little capacity -- heavy sulfation, or heavy plate erosion.
Seems that some smallish SLA batteries are incorrectly called AGM, when they are probably really Gel. Some Gels can be permanently damaged by excessive charge current (which can form gas bubbles, isolating the plates from the gelled electrolyte). This may not be the situation
you noted.
To me, running a long Absorb stage every 10 - 14 days, should ensure that the batteries are getting a full charge, at least at those times, and this will help get/keep the two strings in better balance, without this long Absorb.
We do not do a real Load Test on the Flooded banks here, but do discharge the banks to 80 percent SOC, or a bit lower, and measure the terminal voltage of each battery, as a check for infirmity. The most common load at the 20-hour Rate, by using portable 1500 W 120 VAC electric heaters, as you alluded to.
Am still not certain just how well EA ending Absorb really it for most AGMs. Some manufacturers use a vanishingly small EA value, or a rate-of-change in this current, rather than an absolute percentage of C.
And, Lisa, would guess that 12.90 V rested, is nominally about 95% SOC. Having parallel strings could mean, that batteries may need a longer rest, as any imbalance in actual SOC of batteries in each string, actually means that the higher SOC string will be discharged, while it is charging the other string during the first part of the "rest" (IMO). This could add a bit more uncertainty in the resting voltage, and required rest time.
As noted before, SOC readings are really approximations, and need not be taken too seriously. IMO, they are not absolutes, just estimates. And, when Skipping days of charge, the longer since a full-charge (and the Reset to 100% SOC), the greater chance for accumulating errors in the actual battery SOC, vs the SOC that is calculated by the Classic, using the WbJr.
I am no expert on batteries, especially Sealed batteries. All just IMO, FWIW, Thanks, Vic
Justin, Larry, Vic -- thanks very much for all your input. It's really a huge advantage to get input from people who've had experience with these systems.
I feel pretty confident at this point that my bank is not on its way to ruination any time soon. But I will test them with an extra heavy load and see how that goes.
So, around mid-day today I plugged the vacuum cleaner into the inverter and had it on for 5 minutes. This was on top of the usual load, so as to make sure to draw from the batteries. After turning on the vacuum the overall voltage dropped by 1 volt pretty fast but then seemed to slow up. I tested each battery while the vacuum was still on -- all the batteries remained perfectly uniform. Batteries never went below 12.46v.
Hi Lisa,
Assume that the Classic was in Float, when you ran this test …
You could switch the Classic Mode=OFF, so all of the loads would be supplied by the batteries. The WB Status page will tell you how much current is being drawn from the batteries.
The relatively quick drop in battery voltage is probably mostly from, what is called Surface Charge. Lead Acid batteries are affected by this. Your batteries were probably being Floated (assumed), at about 13.7 V per 12 V battery. So it takes some time to remove this surface charge. The removal of this takes a bit of time, and the time depends on the amount of the current being removed from the batteries. Resting a battery (for hours -- no charge, no load) allows the surface charge to dissipate, and so on.
Later, Vic
Oh, that's good to know. Yeah, the batteries popped right back up to float level (27.3) as soon as the vacuum was turned off so it was obviously not a true discharge. However!! I just a few minutes ago remembered that I had put the batteries on the vacuum cleaner for five minutes or so back when we first hooked up the batteries to the inverter - this was a few months ago and we were just seeing if the inverter was working. PVs weren't hooked up yet. So I've already kind of done this test. The batteries had been in rest for a week, and all of them discharged the same, and as I remember, all of them discharged very little.
Anyway, when I get around to testing them (more stringently) I'll remember to do it after they've rested overnight & before they bulk to float with Classic off. Today wasn't a waste of time though - I got my kitchen vacuumed.
Thanks for the answer Vic!