I put this question at the end of another post, then realized it should really go in a separate post on the Forum.
I have one more problem in setting up a new KID controller that is driving me crazy: The battery mfgr gives no value for me to enter in the "Rebulk" parameter. My Absorb is set to 29.1V, and Float is set to 27.9V
Do I set the Rebulk a certain amount below one of those voltages, or is there another way to come up with the correct value to enter???
Anyone have some help for this please?
Thanks! Nick
UPDATE:
I finally got a hold of a Deka solar battery tech on the phone just now. She said to use 28.2V as the REBULK VOLTAGE setting, which is just a tad below the low end of Deka's published Absorb Voltage setting for a 24V system using their 8L16 flooded batteries.
Hopefully this might help someone else on the Forum in the future
Nick
Quote from: nlt999 on August 20, 2015, 01:48:04 PM
UPDATE:
I finally got a hold of a Deka solar battery tech on the phone just now. She said to use 28.2V as the REBULK VOLTAGE setting, which is just a tad below the low end of Deka's published Absorb Voltage setting for a 24V system using their 8L16 flooded batteries.
Hopefully this might help someone else on the Forum in the future
Nick
Hi Nick,
Thanks, but believe that the Deka Tech does not understand the use of ReBulk.
Believe that the suggested 28.2 V ReBulk is too high. ReBulk should really be below the Float voltage setting.
ReBulk begins an additional charge cycle, on a given day. And it is triggered when the loads exceed the ability of the charge power source (usually PVs), and the CC cannot maintain the Float voltage. Under these conditions, when the ReBulk setpoint is reached, a new charge cycle begins.
Here is a bit more discussion on ReBulk:
http://midnitesolar.com/Forum/index.php?topic=2295.0
Thanks, Vic
Thanks once again for your input Vic!
This is getting very frustrating, trying to get accurate info on how to set the various parameters in the KID.
And now it appears that our installer may have gotten the WhizbangJr installed backwards (not sure on this, still checking it out, but our readings indicate that he well may have!). If so, we probably won't be able to get him back to correct it before my brother leaves MT for the off-season. I am not so concerned about the readouts being backwards polarity, but AM concerned about the End-Amps function not working correctly for the 9 months or so until my brother gets back there next year. I'm thinking that maybe we can change the End-Amps parameter from the current setting of 3.7V (at the battery tech's suggestion) to MINUS 3.7V (if the KID will allow us to go negative for that parameter). That would compensate for the backwards polarity reading coming from the WBJR to allow correct operation of the End-Amps function until we can get things straightened out next year, when hopefully I can get there myself. Does this make sense to you Vic???
If the battery manufacturer can't give me accurate info, then I'm really in trouble since a lot of the parameters say to use mfgr info to set them.
Beginning to think this forum may be the most reliable source of information, and you guys are great at offering help..... really appreciate that!
Thanks for the explanation of the ReBulk operation Vic, and thanks for the link to the previous posts (I missed them somehow).... I've read through all of that and that helps too!
I've sure got a lot of learning to do!!
Nick
Nick can you use a screwdriver (or 2) and do you know where the battery and PV disconnects are?
In my opinion Rebulk is not very valuable for a solar controller that does 3 stage charging every day. The reason is if the PV isnt strong enough to keep the voltage at float then what good will it do to go to bulk? Now Hydro or Wind or using Skip days I believe it is very valuable.
Rebulk has to be set lower than float and will generally be set a few volts lower than float.
For instance on my 12v office system I have 375AH of Trojan L16 flooded. I have small loads so i use skip days. I have it set to do a bulk charge every 7 days. So settings look like this on mine:
Absorb Volts = 14.8v
Absorb time = 3 hours
End Amps = 5 amps
Float = 13.6v
Re-Bulk = 12.1v
So what this does is:
A- Only does a full 3 stage charge once every 7 days unless the battery falls below 12.1v (Re Bulk) then it will do a new bulk charge
B- Will terminate a bulk charge early if the current into the battery is less than 5 amps (End Amps)
Quote from: nlt999 on August 20, 2015, 09:04:00 PM
Thanks once again for your input Vic!
This is getting very frustrating, trying to get accurate info on how to set the various parameters in the KID.
And now it appears that our installer may have gotten the WhizbangJr installed backwards (not sure on this, still checking it out, but our readings indicate that he well may have!). If so, we probably won't be able to get him back to correct it before my brother leaves MT for the off-season. I am not so concerned about the readouts being backwards polarity, but AM concerned about the End-Amps function not working correctly for the 9 months or so until my brother gets back there next year. I'm thinking that maybe we can change the End-Amps parameter from the current setting of 3.7V (at the battery tech's suggestion) to MINUS 3.7V (if the KID will allow us to go negative for that parameter). That would compensate for the backwards polarity reading coming from the WBJR to allow correct operation of the End-Amps function until we can get things straightened out next year, when hopefully I can get there myself. Does this make sense to you Vic???
If the battery manufacturer can't give me accurate info, then I'm really in trouble since a lot of the parameters say to use mfgr info to set them.
Beginning to think this forum may be the most reliable source of information, and you guys are great at offering help..... really appreciate that!
Thanks for the explanation of the ReBulk operation Vic, and thanks for the link to the previous posts (I missed them somehow).... I've read through all of that and that helps too!
I've sure got a lot of learning to do!!
Nick
Hi Nick,
First, ReBulk is really a specific manner in which a CC manages charging batteries. So, it is really not something that a battery manufacturer may be aware of ... some Solar equipment manufacturers, call this function something different (like Schneider's term "Recharge"), so battery mfgs may not follow all of these details of chargers. AND, each system may have certain characteristics that would require the ReBulk to be set differently than most other systems.
Ryan - Halfcrazy - had an interesting example of RB in one of his systems, but your needs will probably be different.
Regarding the polarity of the WB's battery current, guess that you are saying that during a Bulk stage, for example, that with light loads on your inverter, that with good sun on the PVs, that you are seeing a negative current reported from the WB ?? This would, indeed, show that the WB is connected backward. Could you please confirm that this is what is being seen from the WB?
The correct installation of the WB is fairly simple, although there can be mechanical issues around the Shunt, where is can be difficult to fit the WB onto the Shunt due to the way that cables are routed, etc.
Thanks, Vic
Hi VIc!!
We have determined that the WBJR is indeed installed backwards by looking at it visually. Also, when we put the KID in EQ mode with light inverter load, the current indication was -7.6A (negative), further confirming the reversed installation.
Since my brother has to leave the site tomorrow and won't return until next June, I have decided that the best temporary solution is to turn the WBJR OFF using the menus. My brother is not technical, and not a particularly handy-type person, and is running out of time before leaving as well, so I don't want him to attempt to reverse the WBJR himself, particularly with the rats-nest of an installation that was done inside the breaker box where it is mounted.
My next problem is figuring out a logical setting for the Absorb timer, since the WBJR won't be there to cut Absorb time short as it would normally. There will be no external loads on the system over the winter (inverter etc turned OFF), so the only drain on the batteries will be self-discharge. As long as the weather stays decent I'm sure the KID will just stay in Float mode and the batteries will be fine. However, if they get an unusually heavy snow that covers the ground-mounted panels, or an extended time of very cloudy weather, I'm not sure what will happen. The KID default Absorb timer setting was 120 min, but Deka recommended 12 Hrs (720 min) which is what we changed it to. I was not concerned about the long Absorb time because I figured the WBJR would cut it short anyway. Deka gave me a formula for determining Absorb timer setting, but it is based on AHrs-used and average current-input, so I don't know how to apply that in this situation.
Do you have any suggestions??? We are only concerned with maintaining battery-health during the off-season right now.
Thanks again! Nick
Hi Nick,
First, I have no direct experience with off-grid systems in cold, snowy climates ... but others have recommended tilting the South-facing PVs up to a very steep angle to aid in shedding snow ... hopefully there is a reasonable distance twix the bottom of the PVs when so tilted, that the snow will not pile up and shade the PVs.
The batteries should be cool/cold, which will reduce the self-discharge.
Of course you will NOT want a long Absorb.
You might want to Float only on many days ... forget if the KID has Skip Days, yet ...
Some feel that batteries that are always Floated will not stratify, and that makes some sense to me.
If you can, could you join the Wind-Sun Forum, and ask about over-Wintering Flooded batteries ... realize that June in not "Winter", and this will be a very l o n g time for batteries to not be attended, which could be an issue.
Wind-Sun Forum:
http://forum.solar-electric.com/
That Forum is fairly active, and there have been a number of discussions about Winterizing Floodeds.
More Later, Good Luck, Vic
Thanks once again for responding Vic!
I did join the other forum and am waiting for any advice, but running out of time to set things up unfortunately. I tried to find previous posts about winterizing but couldn't find any... maybe I searched incorrectly... will try again.
Does the KID's default Absorb time parameter of 120 Min seem too long to you? We need to keep the batteries charged, but don't want to overcharge since we won't be there to add water to the cells. Also, the ReBulk Voltage will be set for 25V.... do you think that will cause too many full charge cycles (that we should set that voltage lower)??
Nick
Hi Nick,
Saw your Post on Wind-Sun, had hoped that some of the members in the far North would have a chance to reply.
I wonder about only Floating the bank.
The very long absence seems to me to be a fairly large risk.
Have some L-16s here, so, know that thinking about weather your brother could possibly take the batteries with him for the duration ... this seems like a long shot.
But, you are thinking about being gone for 10-ish months.
Short of removing the batts, is there ANY way that someone could try to visit in about April? Do not know anything about the nature of the site, but as the weather warms, there are concerns about water loss, and the possible need of giving the batts a freshening charge, and so on.
Saw your ReBulk value of 25 V ... seems a bit high, but, there is no real time to test some of the variables.
Could you please try sending Ryan - Halfcrazy a PM or e-mail, and ask for his input? He lives in Maine, and has mucho experience with off-grid Solar nuances.
More later ... Good Luck, Vic
Thank you all for your input...... I really appreciate it!
No way can we haul the batteries home for the winter, the installation is on an island and the house about 100' above the water and only accessible by boat ....... can't just back up the car and load up the batteries!
I wound up having my brother set up the KID as follows:
Absorb Voltage: 28.8 (lowest-end of battery mfgr specs)
Absorb time: 30 minutes (No End-Amps control available)
Float Voltage: 27.6 (lowest-end of battery mfgr specs)
EQ Voltage: 30.3 (mfgr recommended)
(KID only has MANUAL EQ, no automatic EQ)
ReBulk Voltage: 24.5V ( I think about 80% SOC level)
Had him check battery water levels
Had him run manual EQ last thing, after all loads were turned off
He will check the water levels and run a manual EQ first thing upon arrival next year, before turning on any loads.
We are crossing our fingers that this will work well enough to get us through this winter.... we'll see what he finds when he returns next summer! Thinking we may upgrade to the Classic controller, or an Outback controller if this doesn't work out well, where we may have more setup options, such as Skip Days.
Once again, thank you all for your responses...... greatly appreciated! Nick
Skip days is nice, We could add that to the kid I am sure. I will run that feature up the flag pole. (FYI the Outbacks do not have skip days)
Quote from: Vic on August 21, 2015, 02:26:12 PM
Some feel that batteries that are always Floated will not stratify, and that makes some sense to me.
I think there is good evidence that "always floated" batteries do stratify.
If "always floated" means solar powered, then there is daily/nightly cycling that leads to stratification.
If "always floated" is taken literally, then there is most certainly stratification. For example, an Iota battery charger, grid powered, holding a battery at float forever, will automatically do a weekly Equalization (EQ). Iota's definition of this EQ is basically an absorb cycle at absorb voltages, but their rationale for doing it is development of stratification in a floating battery. Other manufacturers of "3 stage" grid powered battery chargers do the same as Iota.
Many forklift battery chargers do not have a float function. They are designed to be charged overnight, and when the charge cycle is completed the battery is charged and the charger shuts off. No float. The battery will do fine just sitting there waiting a day or two until the next shift.
The reason we have float in an off grid power system is so that the solar can power loads during the day when the batteries are already charged. If the controller just shut off when the batteries were charged (like the forklift battery charger), the batteries would then carry the load while the sun was still shining.
If a battery is held at float, below the gassing voltage, there are currents flowing. These currents are flowing through the plates and electrolyte. If there is any stratification (inevitable), the stratification means that the lower plates have a different electrochemical potential than the upper plates.... think of each cell as two batteries (upper and lower) in parallel. The currents that flow between the upper and lower plates are part of the battery's self discharge. When a battery is held at float voltage, these internal current flows will continue as long as there is any stratification. Since the lower plates have a higher electrochemical potential than the upper plates, the current into the battery (at float voltage) may preferentially pass through the (lower potential) upper plates.
Bottom line: flooded batteries need to be stirred occasionally. Long term float is not good for them.
Thanks everyone!
A few more notes and questions:
I asked a tech at MidNite whether Auto-EQ might be added to the KID in the future. He said NO, one reason being limited memory in the KID compared to the Classic. Considering that, is there any chance that a Skip-Days function might be added?
Thanks for the in-depth explanation about 'Always-Floated' and stratification!
Do I understand correctly that each morning, when the sun wakes up the KID it automatically starts a 3-stage charging cycle (Bulk, Absorb, Float)? If that is true, would that not be enough to prevent long-term stratification??
We discovered that our system installer put the WhizbangJr in backwards, but it was too late to be able to get him back to correct the problem before we had to leave for the season. I disabled the WBJR using the menus and we will get that problem resolved next year. Once the WBJR is working correctly, when we look at the WBJR status screen where it shows the net current into/out of the batteries, if the KID is in Float mode and there is enough PV power available to balance the loads, should we expect to see ZERO Amps showing on that status screen? (in other words, the Float charge current would be just matching the current we are drawing out of the batteries at any moment)
Thanks once again for all your comments and input! Nick
Quote from: nlt999 on August 23, 2015, 12:25:11 PM
Once the WBJR is working correctly, when we look at the WBJR status screen where it shows the net current into/out of the batteries, if the KID is in Float mode and there is enough PV power available to balance the loads, should we expect to see ZERO Amps showing on that status screen? (in other words, the Float charge current would be just matching the current we are drawing out of the batteries at any moment)
A Flooded battery that has just been fully-charged, and is then in Float, will need some current flowing into the battery to maintain any reasonable Float voltage.
There will be a period of time, just after the transition to Float, when current flows from the battery (negative current) to supply any load -- like the Tare of the CC, in your case. Once the Tare losses and self-discharge remove the Surface Charge, there will be a small current into the battery that is needed to maintain that reasonable Vfloat voltage.
On the old Flooded battery banks here, this amounts to about 0.3% of nominal 20 Hr Capacity, at the manufacturer's recommend Vfloat. There should be some temperature effects on this current.
Vic
Interesting comments from vtmaps concerning forklift batteries.
I would agree that non floating charged banks do stratify and this appears to reduce charge capacity. A local company with 3 forklift and 12 sets of batteries (8 by R220s per set for 48V) can have a couple of charged sets unused for a week or more.
The owner goes for fishing weekends about 300Ks to his rented lakeside home, no grid, so takes one or two sets in trailer with 1k5 inverter and a couple of 300watt PVs with KID, sets it up mostly for lights, small tv and bar chiller. (just keeps sets in trailer)
He always takes poorest performing set and the journey shakes up the R220s and he says its like they have a new lease of life when he gets back and grid charges them again.
He puts it down the the good shaking/abuse they get on the journey that airs and mixes the acid.
..sorry for floating slightly off topic ???
dgd