From my reading, the 'battery efficiency' setting for the WBjr is a compensation for how many AH need to be measured going into the battery opposed to how many actually count towards the charge.
If the battery were 100% efficient then every AH measured going into the battery would actually be stored for later usage. But batteries are not perfect, so the efficiency setting allows us to compensate for power that is lost in the process.
I have also read in many of the 'Absorb Time' discussions that when you see the falling curve of amps going into the battery start to level off, the absorb is done. When you drop out of bulk and into absorb, a constant absorb point voltage is held, and it is held by dropping off the current flowing to the battery, thereby holding a constant voltage. Once the current levels off, then absorb is done. Those that use 'Ending Amps' to terminate absorb phase rely on this fact.
So, I'm reasoning that if my SOC reaches 100% and my measured current going into the battery is still declining, then I have my 'battery efficiency' set too high. The WBjr believes that enough AH have gone into the battery to fill it, yet those actual amps are showing that it is not full. If I lowered the 'battery efficiency' setting, it should slew the SOC towards the leveling off of the charge amps.
Note that every time I have referred to AH going into the battery, I am using the WBjr amps, not the classic amps, so I am only talking about amps going into the batteries, I am not including amps going to loads.
Please look at this clip of a sample day's charging. This clip shows the WBjr amps going into the batteries curve (orange line) and the SOC (blue line). I have also placed a vertical line at the point where I feel the charging amps have leveled off, indicating when the absorb phase should really be completed. As you can see, the SOC has been at 100% for a considerable amount of time prior to that point. This leads me to believe that I need to lower my 'Battery Efficiency' setting. It is currently at 94%, and my batteries are 4 years old (FLA GC2).
Thanks for all comments and shared opinions. For me, this is more about my education than having a perfect SOC.
Hi o-g-g,
Being no expert, let me say the following;
FLAs are not particularly efficient. IMO, 94% is way too high. The common wisdom about FLA efficiency is that they are about 85% efficient. AND, as they age, they are probably not THAT efficient.
Also, IMO, believe that one needs to wait until there has been no change in the battery charge current for a period of time, like about 20 of so minutes.
Seems to me, that your Orange line still has some slope to it.
Guess that the lumps in the Orange line are from varying loads on the system, with some reasonable voltage drop between the CC and battery (?? ?).
More Later, good question, Vic
Thanks Vic,
I've seen 2 conflicting opinions for the starting point for the efficiency setting; 85% and 94%.
If there is agreement that my graph shows I'm too high, then my next attempt was going to be 85% and see what that looked like.
Those bumps in the orange WBjr amps line are my fridge kicking on and off. The ONLY item I have running on an inverter is the fridge, which is actually a new, efficient, 5.5 cubic foot chest freezer repurposed to a fridge by using a brewer's thermostat. Everything else in the house runs at 12 volts.
So, I'm going to config for 85% and see the difference, and anyone else that has a comment or suggestion to make, please chime in.
Thanks!
o-g-g,
AGM batteries, which are considerably more efficient than are FLAs run around 94% efficiency, as I read it.
BUT, I am no expert. With FLAs, the great thing, is that we can easily actually measure the SOC with a Hydrometer. So, on the systems here I really pay no attention to anything other than Net Ah, on the first morning after a full-charge (as we Skip three days, and Charge on the fourth).
Good Luck, Vic
Ogg,
Where you have drawn the vertical line, where the amps tail off, what is the actual amps reading and what is the Ahr rating of your battery bank?
There is no time axis on the graph so what is the time elapsed from reaching 100% soc to your vertical line.
As an aside I never found fiddling with the battery efficiency figure by +- 5% to make any difference and even if the absorb timing is too short the battery still charges towards a real 100% soc when in float
4 year old FLAs I would tend to keep about 90 to 93% efficiency
Just MHO
dgd
Quote from: off-grid-geeks on July 08, 2016, 03:43:43 PM
From my reading, the 'battery efficiency' setting for the WBjr is a compensation for how many AH need to be measured going into the battery opposed to how many actually count towards the charge.
If the battery were 100% efficient then every AH measured going into the battery would actually be stored for later usage. But batteries are not perfect, so the efficiency setting allows us to compensate for power that is lost in the process.
Thats about right. The "battery efficiency" setting is the
coulombic efficiency, that is to say its not the Wh in / Wh out, thats much lower. Wh for Wh you account for both current and voltage, and voltage is lost from heating/internal resistance, and that isnt accounted for in the Ah efficiency.
Unless bob is going to explain his algorithim, its assumed to be a two factor thing, the battery effiency setting scales the charge Ah, and the temperature setting scales the SOC. Theres no peukart, or at least he never mentioned it.
The thing about the AH efficiency is it varys by SOC. During bulk it is 100% efficient. (Each Ah you put in stays in. though you still have a Wh loss). Once absorb starts the (FLA) battery starts to bubble and gradually the AH efficiency falls, tapering to zero once float is reached. The coulombic energy is lost to hydrogen gas production.
The number one hit on google for lead acid battery efficiency gives you the first grpah below, which shows this clearly. (http://electronics.stackexchange.com/questions/153517/what-is-the-charge-discharge-watt-hour-wh-efficiency-for-lead-acid-batteries-a)
That article also references a sandia study (http://www.otherpower.com/images/scimages/7427/Lead_Acid_Battery_Efficiency.pdf), (which is a shockingly poor study when you examine it closely), but it does confirm that battery efficiency depends on where you run your system. For 95% of the year our battery achieves float every day, and for 80% of the year it gets several float hours each day. And our daily drawdown is around 10-15%, thus the battery spends its entire life in the less "efficient" part of the charge cycle. Thus you should factor this into your efficiency setting. However who cares whether your SOC is 90 or 95... its when the bank is low that you need reliable SOC figures. Thus it was our recent experience here to have a month of usually sh*tty weather and we went 21 days without float. This showed me how the simple "average efficiency" falls down. During this kind of lower PSOC cylcing, the efficiency is much higher.
And... AGM changes everything. According to one Rolls document, AGM batterys are 99% AH efficient. This is because there is no gassing. The hydrogen is reabsorbed using catylysts.
My quick analysis of this last month indicates that i have to increase the efficiency to 100% to get the SOC back to 100% after those 20 odd low SOC days. (This analysis used a 15min sample interval hence its rough). See graph below (blue curve was with classic eff set to 94%, and SOC drifted a full 25%, the other two curves are my crude modelling). I have 1sec data, and i will probably redo the analysis using it, but its a bucket load of data, and excell wont handle it, so will need some code. But it somes seem to indicate that 99% is in the right ball park for AGM.
Quote
I have also read in many of the 'Absorb Time' discussions that when you see the falling curve of amps going into the battery start to level off, the absorb is done. When you drop out of bulk and into absorb, a constant absorb point voltage is held, and it is held by dropping off the current flowing to the battery, thereby holding a constant voltage. Once the current levels off, then absorb is done. Those that use 'Ending Amps' to terminate absorb phase rely on this fact.
This is a separate issue. Its not easy to see the levelling off point on a curve thats (somewhat) logarithmic. The exact level that the charge acceptance current/power reaches depends on the battery type ( again lower for AGM), and the batterys age. I use 0.005C + 0.5A for our EA setting, and that works well. For FLA this might be more like 0.02C. Even so during the summer i sometimes see it taper down to as low as 0.0015C. You just have to use a pragmatic compromise. But that also shows you how a decent post absorb float can really put the topping on your absorbs. (Sadly the classic cant be configured to do a post absorb EQ/finish, another subject). See todays curve, went to float at 15:50. (This was with WBJr efficiency set to 99%, and it started the day at 77%. Also notice that there is no discernable jump in the SOC at float.
Note that if you set you EA too low it may not trigger, or, trigger less often thus youll get less frequent SOC reset.
Quote
So, I'm reasoning that if my SOC reaches 100% and my measured current going into the battery is still declining, then I have my 'battery efficiency' set too high. The WBjr believes that enough AH have gone into the battery to fill it, yet those actual amps are showing that it is not full. If I lowered the 'battery efficiency' setting, it should slew the SOC towards the leveling off of the charge amps.
On an average efficiency basis: If the SOC jumps up at float, then the efficiency is set too low. If it gets to 100% before float its set too high.
Quote
Note that every time I have referred to AH going into the battery, I am using the WBjr amps, not the classic amps, so I am only talking about amps going into the batteries, I am not including amps going to loads.
Please look at this clip of a sample day's charging. This clip shows the WBjr amps going into the batteries curve (orange line) and the SOC (blue line). I have also placed a vertical line at the point where I feel the charging amps have leveled off, indicating when the absorb phase should really be completed. As you can see, the SOC has been at 100% for a considerable amount of time prior to that point. This leads me to believe that I need to lower my 'Battery Efficiency' setting. It is currently at 94%, and my batteries are 4 years old (FLA GC2).
Thats right.
Quote
Thanks for all comments and shared opinions. For me, this is more about my education than having a perfect SOC.
The above is probably too much information, but it is a kinda interesting subject.
Is was Trojan not Rolls:
http://www.trojanbattery.com/Tech-Support/FAQ/BatterySelection.aspx
This is an interesting Topic.
Am an agnostic when it comes to Battery Monitoring devices, as most of them do not have enough parameters to really model the battery being used. And, who would know enough to enter all of the parameter data, anyway ...
It is correct that even FLAs approach 100% efficiency, at least for about 80% of the Bulk (or so ... depends) stage, and during Absorb the efficiency decreases to essentially zero at the last part of Absorb.
Personally, I would guess that AGM batteries do gas, and this gassing is much of the inefficiency of AGMs, but the Catalyst recombines the Hydrogen and Oxygen back into water. But, it is the breaking down of water even in AGMs that is the dominant loss of efficiency, even if, the gasses are later recombined. Believe that AGM and Gel LA batteries are Lead-Calcium (plus some other trace metals) and gas considerably less than do Lead-Antimony batteries. IMO, Gel batteries have the maximum charge voltage a bit below the Gassing Voltage.
Have never used AGMs, and in every other way, I am NO expert on any of this ... and there are SO many variables. "It all depends ..."
FWIW, Vic
Thanks for all the good input and great discussion!
DgD, the amps at the vertical line are at 12.2 amps. The bank capacity is 440 AH. The elapsed time from 100% SOC to the vertical line is 1:15
I'm now running with a setting of 85% to see what the difference is.
Ogg,
From that data the charge is levelling out between 2 to 3% of battery capacity which is a good indication of a healthy FLA battery.
I would set up the Classic for an EA setting of 13amps and run an efficiency of 93 for a while and see if the SOC aligns closer to absorb termination.
But do remember this is not an exact science and as others have said there are just way too many variables at play. It doesn't really matter too much if SOC reaches 100 before absorb ends
I have seen my FLA bank after not completing absorb for several days then jump from 95 to 100 when an absorb cycle completes, other times 100% is reached well before absorb completes
Dgd
Quote from: dgd on July 09, 2016, 04:26:41 PM
I have seen my FLA bank after not completing absorb for several days then jump from 95 to 100 when an absorb cycle completes, other times 100% is reached well before absorb completes
Exactly. Depending on how low the SOC got the efficiency setting will either over compensate or under compensate.
Vic, i also am wary of battery monitors. However with AGM, you dont have many choices, and its only now that the Mrs can see the SOC on the kitchen wall in 36pt font, that she really has ANY sense of whats going on, whether she can run the little electric oven we have, whether she can go mad with the vacuum, or just do a quick lick.
Heres how i see coulombic efficiency. An amp and and amphour are comprised of coulombs. A coulomb is a finite number of actual electrons. In a closed electric circuit those electrons can therefore go near else but around the circuit. Hence coulombically its 100% 'efficient' right? In a FLA when hydrogen is produced and vented to the atmosphere, the battery in the circuit becomes a hydrolysis generator, and thus electrons become lost to hydrogen (and oxygen) atoms. Therefore the way i see it is if the gases are recombined then the electrons are not lost, and the efficiency is more or less 100% as with the closed circuit. Ill be able to see after running 99% for the next couple of months how this works out.
Also agreed about the difficulty of defining and programming SOC parameters, but all i know is that our classic was reading 25% too low, when it was reporting a SOC of, at its lowpoint, 17%. And that messed with her mind, and i had to translate the figure to what i thought it to be.
What i thought it to to be, was derived from, noticing the progress of partial absorb tapers during the month, and, Blackbox each day reporting the highest battery voltage between 5am and 5.30am. This is quasi 'rest voltage'. It obviously isnt true rest voltage, but, it lets the fridge cycle off. If i correlate these figures during this event, this sort of tallys with the pink 100% curve on the graph.
If i was to try to write something for the manual, it would be (provisionally):
"For FLA start with 89%, and for AGM start at 99%. Then adjust as needed by observing your charge cycles. The SOC resets each time the battery floats, and if the SOC jumps up at float, then the efficiency is set too low. If it gets to 100% before float its set too high. However be aware that, the efficiency varies by SOC, so use a setting that gives the best result in the band that you tend to cycle your battery. It also varies by battery age, and ultimately, any battery monitor is just a guide".
Maybe this is a good time to vent my little rant about battery monitor shunts. It seems to me that all battery monitors have a basic flaw, by using only one shunt. For 25 extra bucks adding a second shunt would produce a much better picture of whats happening to the battery. One shunt would be in the load path, and the other in the production path. From the first time i ever saw a battery monitor, the question was always in my mind, so that battery is currently charging, but how much of that is production and how much consumption?
Below is the current blackbox home screen. Of the three panels, the energy corner shows charge watts, load watts (i have to fudge this by using use both classic amps and Wbjr amps), SOC and Vbat (for reality check). The scrolling graph shows the last 10mins of production and load watts. The weather helps you make load decisions, and the time, well its the only accurate darn clock in the house.
Those four figures show that the kettle has just boiled, but that otherwise theres just base loads, and that the battery is near end of absorb.
Dgd,
Yep, I read awhile back that chasing an accurate SOC is nothing but frustration. I'm not really trying to do that, I just wanted to understand the interaction of the battery efficiency setting and SOC. And thanks to all the responses, I see that I am understanding it.
I'll play around a bit to just to learn more, but will settle for 'close enough'. when I'm done.
Quote from: zoneblue on July 09, 2016, 07:51:09 PM
Maybe this is a good time to vent my little rant about battery monitor shunts. It seems to me that all battery monitors have a basic flaw, by using only one shunt. For 25 extra bucks adding a second shunt would produce a much better picture of whats happening to the battery. One shunt would be in the load path, and the other in the production path. From the first time i ever saw a battery monitor, the question was always in my mind, so that battery is currently charging, but how much of that is production and how much consumption?
... moving a bit off topic here ???
You seem to be referring to a battery monitor plus a load monitor system and somehow integrating the data from both to provide a more complete current usage picture.
With the current Classic's shunts it takes some simple calculations to figure out load and tare usage.
With two or more charge sources its getting more complicated.
I did think that a 2 Classic system would allow a second shunt/WBjr combo to measure other DC current, eg an inverter load, but it seem this has its own complications.
I found the easy way was to just add other DC and AC current measuring devices placed where needed.
One DC device, the ACS758, proved simple to use with Arduino/Cubie/rPi/BBB, its a high side +ve line device. These are available up to bi direction 200amps, I use a 150A uni type to measure DC usage of my 24v 3.3Kw inverter.
With an Uno or Mega ethernet connected there could be several AC and DC current and maybe an AC voltage/Hz sensor, plus additional temperature probes or other sensors making data available to your Black Box system monitor (in a similar way your Arduino based weather monitor does)
dgd
Latest update.
I've been using an ending amps of 13 amps, which is 3% of the C20 rating, as was suggested earlier in this thread.
The WBjr amps absorb curve does level off at that point.
I've been chasing the elusive 100% SOC to match this EA point. I know, I know, its not important. I'm just doing it for the education.
Today I got the two to coincide. The battery efficiency setting that got me to that point was 70%.
Seems low. 4+ year old batteries, Full charge is showing an average SG of 1260.
But it works.
Learning a lot!
Quote from: dgd on July 10, 2016, 11:59:33 PM
.. moving a bit off topic here ???
A bit!
Quote
You seem to be referring to a battery monitor plus a load monitor system and somehow integrating the data from both to provide a more complete current usage picture.
With the current Classic's shunts it takes some simple calculations to figure out load and tare usage.
The problem is that the classic amps and the wbjr amps are not averaged in the same timeframe (a product of the modular nature of the WBJr), and so you get these odd spikes and negative load data. The classic amps is also not as accurate as the WBJr, and theres related issues with teh classic tare.
Quote
With two or more charge sources its getting more complicated.
I did think that a 2 Classic system would allow a second shunt/WBjr combo to measure other DC current, eg an inverter load, but it seem this has its own complications.
Yeah ive never tried followme, so not sure how that would work. Never mind adding other charge sources, as you say.
Quote
I found the easy way was to just add other DC and AC current measuring devices placed where needed.
One DC device, the ACS758, proved simple to use with Arduino/Cubie/rPi/BBB, its a high side +ve line device. These are available up to bi direction 200amps, I use a 150A uni type to measure DC usage of my 24v 3.3Kw inverter.
With an Uno or Mega ethernet connected there could be several AC and DC current and maybe an AC voltage/Hz sensor, plus additional temperature probes or other sensors making data available to your Black Box system monitor (in a similar way your Arduino based weather monitor does)
Ok so im interested, but.... In order to keep EA, the existing low side battery line shunt needs to stay. Thus one other shunt either in the charge or the discharge line, ought to do it. However to account for both shunts in the same time frame, i guess that takes us back to a matched pair of shunts and instrument amps, one for each of charge and discharge paths. That means 3 shunts, and 3 lots of 10x mV voltage drops. Joy.
Ok so use the WBJr shunt, with another amp. Thats down to two. Both in the low side, or one low and the other high? We kinda want to avoid negative bus potential differences, so maybe high side as you said.
Quote from: zoneblue on July 14, 2016, 07:21:34 PM
Ok so im interested, but.... In order to keep EA, the existing low side battery line shunt needs to stay. Thus one other shunt either in the charge or the discharge line, ought to do it. However to account for both shunts in the same time frame, i guess that takes us back to a matched pair of shunts and instrument amps, one for each of charge and discharge paths. That means 3 shunts, and 3 lots of 10x mV voltage drops. Joy.
Ok so use the WBJr shunt, with another amp. Thats down to two. Both in the low side, or one low and the other high? We kinda want to avoid negative bus potential differences, so maybe high side as you said.
Yes, I would forget about the Deltec shunt WBjr combo and leave it just for EA.
Two high side acs758, one load one charger but maybe bidirectional for both and at night the classic tare is measureable, the other on inverter/LV loads, although I would keep monitoring device loads with charger circuit as they tend to be permanent but small tare loads, Bi for inverter if it has battery charge capability.
If both are on the same Arduino then timing counts can be identical within millis.
Didn't all this get detailed in the Gregy discussion? (What happened to him?)
Dgd
Maybe moderator should move this 'new thread' to sensors in BB :D
Interesting topic - some good information, my scenario is as follows - I installed new Rolls flooded cell 6V batteries (660 AH), initially I used the Xantrex inverter charger to ensure the batteries were fully charged. Initial specific gravity readings averaged 1270 (1265-1280). I installed the Midnite Kid controller with the WBJR and (4) 100W panels in a series/ parallel configuration. After a month or so of using the solar system to charge the batteries, the specific gravity readings decreased to averaging 1240 (1230-1250), which appears to indicate the batteries are not being fully charged. Settings on the controller are per the manufactures recommendation, Battery Efficiency 94% and End Amps 13.2 Amps (2%). At this point I'm considering decreasing the Battery Efficiency setting and/ or increasing the End Amps setting. Any suggestions?
Hi dmk..,
Changing the Efficiency factor should not change the amount of charging the batteries receive.
Increasing the EA value would result in less battery charging, as the Ibattery DECREASES, as the battery becomes more fully-charged.
What is the Surrette model number for your battery?
What ARE your charge settings -- Absorb, Float and EQ? What is the Absorb time setting?
What is your average total Solar power production per day?
What are the loads on the system.
What is the purpose of the system -- Grid backup, weekend cabin, (etc) ?
Did you Commission the battery bank, per Surrette's recommendations?
Assume that you are running a 12 V system (?).
Appears that even on a 12 V system, you do not have nearly enough PV for that battery bank, BUT, not really knowing the battery model number, it is difficult to determine. If the system is just for backup with few and occasional loads you can get by with less PV power, generally.
Thanks for the answers. Vic
Agreed, the Battery Efficiency setting only changes the displayed SOC number rate of change. It has zero affect on actual charging. With a higher efficiency number, the displayed SOC will climb faster, and a lower efficiency number will slow down the rate of change of the displayed SOC. That's all it does.
Hello dmkkeng,
After doing a bit of sleuthing, guess that this system is on a boat in the PNW.
Looks like you have three parallel strings of 2 6V batts in series. Each batt has about 220 Ah of Capacity.
Is this the battery that you are using (?): http://rollsbattery.com/wp-content/uploads/specsheets/6FS220.pdf
Most Surrette batteries have a fill electrolyte SG of 1.265, but they are normally rated as if the fill SG was 1.280, this would only make a small difference in your EA and AH Remaining. What is the target SG that you are looking for as 100% SOC?
In the past, you mentioned that your normal battery discharge was in the range of about 125 - 175 Ah (each day?), is this still about the daily discharge of the battery bank?
One additional question; How frequently do your EQ the battery, and at what voltage?
Thanks, Vic
dmk, from what has been posted so far it looks like you need to run your generator and do a BULK charge more often and let the solar do the absorb and float portiions of the charge cycle.
Also, how old are the batteries?
\if the have not had in the neigbourhood of ~50 charge / discharge cycles they may not have finished their commissioning period.....
hth
Battery Model #6FS220 (Rolls)
Absorb set to 14.7V
Equalize set to 15.7V
Float set to 13.2V
I don't recall seeing a setting for Absorb time.
One thing I should have mentioned in my post is that the solar system has consistently charged the batteries back to 100% SOC each day - usually occurs well before the sun goes down and the solar cells stop producing.
I was expecting the specific gravity readings to be higher than 1265 at a SOC of 100%.
Originally I was anticipating daily usage of 125 - 175 AH per day however so far, on average, I'm using less than 100 AH per day.
Yes it is a 12V system and yes it is on a sailboat and yes it is a bank of six batteries and yes you have the battery model correct - good sleuthing Vic.
The batteries and solar system were installed May 2016 so they have only been in service for 3 months.
I have not equalized the batteries as I didn't think it was time to equalize.
I was down at the boat yesterday and plugged in my Xantrex charger to see if the specific gravity readings went back to where they were prior to using the solar system to charge the batteries.
The Midnite Kid is indicating is 100% SOC (660 AH) at an average specific gravity reading of 1.240. Per the Rolls manual 100% charge = specific gravity reading of 1.255 - 1.275, 75% charge = specific gravity reading of 1.215 to 1.235, an average specific gravity reading of 1.240 indicates the batteries are only being charged to approximately 80%.
Perhaps the Midnite Kid is not setup properly? With exception of the specific gravity readings everything else appears to be working as it should.
dmkkeng, Thanks for the added detail on your system and settings.
There IS a time setting in the KID ... down a couple of levels in the <battery> menu. There is a new recommendation from Surrette for a 15 Volt Absorb voltage. When EA is being used, this time period will be the Maximum time that the KID will be in Absorb. If the set EA is reached before this max time, the EA value will end Absorb -- it is an OR function, either EA OR Time will end Absorb.
Also, IMO, 2% is a bit on the high side for EA, although if you do increase the Absorb voltage, you might just leave EA at 2%. Also IMO, the actual Capacity of your three parallel strings of 220 A -- 660Ah total -- should be reduced by 5% to accommodate for the 1.265 SG electrolyte verses the 1.280 that is used as the basis for the Capacity spec. Really fly-specs, but that probably would be better at about 12.5 Amps EA. The Surrette batteries, here, ran many years with an EA of about 1% of actual Capacity. This was with a relatively lower Absorb voltage of 14.4 V per 12 V battery.
Battery Monitoring devices give an approximate indication of the actual SOC of a battery bank. They can only be as accurate as is the data entered about the battery characteristics, and there are many parameters about battery charging, discharge, efficiency, etc that we cannot know or enter, that affect the actual SOC and Remaining Capacity, etc.
But you do have Flooded batteries, so you can measure actual SG, as you are doing. These measurements are the Gold Standard for SOC.
The Surrette Battery Manual details Commissioning of a battery bank, recommended Charge parameters and EQ Voltage and frequency. Here is the Link to the Manual, if you do not have a recent copy (as it has changed in about the past month:
http://www.surrette.com/uploads/pdfs/documents/user_manuals/Rolls_Battery_Manual.pdf
An EQ should only be done when the battery is fully-charged, or very close to it.
Are you using the Battery Temperature Sensor (BTS) with the KID? This is very important, as it allows the KID to change the charge voltage based on the actual battery temperature.
So, why not increase the Absorb voltage to 15 V. You might want to try doing some more charging from the Xantrex. Just make certain that its Absorb voltage is set high enough. Often one can run a generator, or shorepower in the early morning to get through Bulk, and into Absorb, and then try to let the Solar finish the Charge. It is often better to not make too many changes all at once, when trying to get batteries fully charged fairly quickly, especially, if one will not be present every day, to monitor any improvements that the changes might make.
You may not really have quite enough PV power to do an EQ, so the generator or shorepower may be needed to do that, but an EQ is important for battery health, when needed.
Good Luck, and please let us know how you are doing. Vic
Vic thanks for the info, I'll likely start experimenting with some of the settings, I sent an email to Midnite and their response was to decrease the battery efficiency setting from 94% to 88% and end amps from 2% to 1.5%. First I'll check the manual link to see if anything has changed with respect to manufacturers recommended settings.
Yes I am using temperature sensor with the Midnite Kid.
When I equalize I will likely do it using the Xantrex.
What should the absorb time period be set to?
Thanks,
Doug
Hi Doug,
The Absorb time setting when using EA, should be longer than you expect the Absorb stage would ever need to be. And, as you know, the required length of the Absorb, will need to be longer with deeper discharge depth of the battery.
The required Absorb time will also be affected by the Absorb voltage, shorter for higher Vabs and longer for a lower Vabs setting. EA needed to fully charge the battery will also vary with Vabs -- somewhat higher EA for higher Vabs, lower for a lower Vabs . Not to try to make things too complicated.
Personally, would set Absorb time about 50% longer than you would ever expect the battery would need at normal Depth Of Discharge (DOD). When using WBjr EA, the Absorb time setting is really there to catch anything that might keep EA from successfully ending Absorb.
As noted, EA, Vabs and the maximum Absorb time are all interactive. This is one of the good reasons to not make too many changes at same time.
Would also suggest to use Surrette's recommended Vabs (it is now a fixed value for a given battery V, as opposed to the previous range of Vabs). And leave EA the same, as you have had it. Your battery has been undercharged for some time. You may well be a bit short on PV power, in general. In these cases, it can be helpful to increase further the Vabs, to use as much of the available solar power to charge the battery as much as possible in the solar day.
If the Xantrex inverter is being run off of shore power, you can try charging with it, in addition to the KID's solar contribution. This inverter should have its own Battery Temp Sensor. If it does not have the BTS, you can manually compensate its charge voltage, from the battery temperature.
More Later, sorry, this may all seem a bit ambiguous. Vic
Increased Float voltage from 13.2V to 13.5V and Absorb voltage from 14.7V to 15"0V per the updated manufacturers specifications. Also changed Battery Efficiency from 94% to 88% and End Amps from 13.2A (2%) to 9.9A (1.5%) per Midnite support recommendations. I will let the system run for a couple of weeks on these settings to see if the Specific Gravity readings change. I was going to leave the Xantrex charger on however it doesn't appear to be charging ... not sure why so I turned it off till I get some time to trouble shoot the problem ... always something ...
Since setting our system to 99% efficiency weve had one three day trip down to 75% SOC, and one two day trip down to 65% SOC. Both times returned to 100% SOC on 0.05% EA perfectly.
So, for AGM, the default WBJr efficiency of 94% is far too low.