Charge terminating based on SOC instead of charge parameters

[Gordon]

Hi Folks,

I have a question pertaining to the Classic 150 being used in combination with the WBJr. I recently installed a WBJr. in my system since I wanted it to be monitoring actual battery current to determine when to end the daily charge cycle. Until now I had parameters set for ending amps that included a little "buffer" in the event that I had a load in the house, like the freezer, and I made sure not to have any large draws occur towards the end of the charge cycle. This was working fine, but I didn't want to have to think about it any more so I installed the WBJr and set the end amps to 2%.

What I saw today was interesting. I noticed the end of the charge cycle was coming, but it was not up to absorb voltage yet and it was already indicating a 97% SOC. I looked back a couple of minutes later and it was already in float. BTW, the batteries are LFP and I have charge parameters set that have been working very well. The only change I made when adding the WBJr. was the end amps. It doesn't appear that the charge cycle completed based on the charge parameters that were set, i.e., absorb voltage, absorb time, and end amps, but rather that it terminated based in its internal calculation of SOC. What I mean is that I would have expected it to go longer to meet the parameters and it doesn't seem to have done this.

I will be able to watch it very carefully tomorrow when the charge cycle nears the end, but I am wondering if anyone may know if it is now ending the charge based on its calculated SOC instead of the charge parameters? And if so, how can I change that to get back to the charge cycle ending based on meeting the charge parameters?

I did update the end amps to be based on "shunt" instead of "classic" according to the instructions and also set the total battery capacity (450 AH) and efficiency (98%) in the WBJr. menu.

Thanks,

Gordon 

[ClassicCrazy]

A lithium battery goes from  absorb to float very fast.
The Classic will terminate absorb by ending amps or absorb time which ever comes first.  The Classic does not use the SOC for charging decisions. You can use the SOC to control things via the AUX contacts though.
On my lithium batteries I am not using ending amps since the absorb voltage alone will get the batteries charged . I use the absorb time to hold it in absorb long enough so bms balancing if needed can occur.
The Classic with regular firmware sometimes would go into absorb prematurely below setpoint. Bob wrote some new beta firmware that makes the Classic voltage more stable for lithiums.
I am using that firmware and it works well, though some people have had a bit of a bug with it showing Soc at 0% after firmware update. You could try it but might want to revert back to other firmware if you get the 0 SOC until Bob fixes that issue.
Otherwise with the regular firmware you just have to watch it when it goes into absorb and then adjust the absorb voltage a bit to compensate.
I use 55.2v for absorb and around half hour for absorb time.
Larry

[Gordon]

Hi Larry,

Thank you very much for the reply. What you described is my understanding of how it should work. It's just that what I observed appeared to deviate from this. I've very familiar with charging the LFP batteries since I've been doing that with the Classic for 2.5 years now. I do have it set with a 15 minute absorb time to allow for the battery voltage to come up to the set point before flipping to float. This is due to an issue I observed when I switched over to LFP batteries. And that was that the absorb timer will start to run a full .3 vdc below the set point, and if the absorb time is set too short it will never get up to the set point. This, combined with the end amps setting, allows me to get the batteries up to voltage while not holding them there for too long when it's a really bright and sunny day.
So when I saw the batteries at 27.4 vdc and came back shortly and it was in float already, I was surprised because there wasn't enough time to get them up to the 28.2 set point and hold them there for a short while to satisfy the 15 minute timer or the end amp setting.
The only possibility I can think of is if they already spent some time in absorb before I looked at them and there was a drop in charge current due to cloud cover at that exact moment that dropped the voltage, and then the cloud went away and the voltage went back up and finished the charge cycle and I wasn't aware of that.
Thanks for confirming that it should still end the charge based on the charge parameters.
My firmware version is 2128 dated 1/11/2017. Could that be causing any issue? I'm guessing that is probably the "regular" firmware that you're referring to. What version is Bob's beta firmware? and how can I try that? I'm thinking this may have been one of those cases that you mentioned of it flipping into float prematurely. I see a firmware version 2193 available on the Midnite website, but since I don't have a Windows computer, I don't think I can get it.
I have done what you recommend, tweaking the absorb voltage and time, and have been using those setting for the 2.5 years now. I ended up with 28.2v absorb, 15 minutes absorb time, and was using a 4% end amps, which I have now reduced to 2% with the addition of the WBJr.
Thanks 

[boB]

If you need to have the battery sit at Absorb for 15 minutes, then you may not want to have Ending-Amps active ?   OR maybe 2% is too high ?

If you came back before 15 minutes were up then the 2% being too high might just be the problem.

I took down the newer software until I can figure out why it has issues here and there.

The software on our web site is the latest in production.

If you would still like to try the latest with Lithium setting here it is.
Remember that after it is installed in the Classic and then MNGP that you have to do a factory VMM (Vulcan Mind Meld) with the MNGP.  When logo comes up, hold down the let and right arrow keys.
Then the SOLAR-WIND-HYDRO questions starts it all out.  You have to wait just a few seconds before it lets you continue.

http://bob.midniteftp.com/K7IQ/Firmware-Latest/Classic-3800/

boB

[ClassicCrazy]

You don't really need ending amps - as the batteries fill up the current they take in comes down. Your batteries should fill up fine with the settings you have.
Larry
 

[Gordon]

Thank you very much Bob and Larry. I'm using the end amps to terminate the absorb before the 15 minutes is up since when I have a strong sun out there it can usually satisfy that parameter in about 10 minutes. I have the longer absorb set so that on those days where the sun is not that strong, I can have the extra time in absorb since it needs the time to get up to the absorb set point. That is because my absorb timer starts counting when the voltage is .3 v below the set point. Is it possible that the firmware with the Lithium settings that you're talking about resolves that issue of the timer starting early?

Either way, I will try to be out there tomorrow to watch it carefully and find out what's really happening.

Thanks

[boB]

I *think* that the beta SW actually help what you are talking about.

If so, you will find that the beta tries to keep the battery voltage closer to the Absorb set point. 

I should say, at the temperature compensated target voltage. If you happened to use one for some reason.

So, there is that.  You can always go back a previous revision, too, if needed.

[Gordon]

Thanks guys!!
I watched it this morning, and it worked flawlessly. It is a bright, sunny day, and at 6 minutes into the 15 minute absorb, it came out of absorb into float based on WBJr. end amps. This is exactly what I was hoping for by installing the WBJr. and using the slightly longer than needed absorb setting. This will give me the extra time when needed on the days with clouds, while taking it out of absorb on the bright days when the current flow drops.
Thanks Again!