Difference in voltage and Amp level JK BMS - Growatt500EP

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So my setup been up running for a month now and first 3 weeks i got batteries recharged back to 100% every nigh. So last week i got more cloudy weather and was operating more on the lower half of battery capacity level. I have 2 x Growatt 500ES with 2 x JK BMS and 2 x 16s 280A batteries in parallel.

So last days i see quite allot of difference on the remain capacity on the batteries, 35AH at the most. I have try close the one battery to get both inverters to charge up the lowest capacity battery but what happens next when I turn back on the other battery Is that the battery who is bring back up now will get very less current and the other battery higher current so the gap between the 2 batteries will grow again. I see some higher voltage on the one battery pack and I see that On the inverter also.

I have no communication between inverters and BMS. Does the Inverters at any level manage charge and de charge levels between the inverters?

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[Skypower]

It’s probably not a problem if you’re under 50% to see a difference in capacity, however there should be very little difference in voltage that the BMS’s report. It wouldn’t hurt to actually see if there actually is a voltage difference between the batteries with a minor load. You should see less than .005 volts between positive and positive or negative and negative. If you want, using quality voltmeter for the truth, you can make adjustments to one or both bms’s in the app. With a quality shunt or clamp meter you could do the same for amperage corrections. I found it’s best to do the with a steady charge at a higher state of charge. Most importantly is when the batteries are full the bms’s should report 99 or 100%. If you make these adjustments you might need to also reset the full state of charge. See relative thread: https://diysolarforum.com/threads/jk-bms-fast-er-soc-learn.68961/

Batteries can report different SOC at different points of use, especially if they are not from the same lot. It doesn’t mean that one battery is better than the other it’s just one puts out at a different point. This is assuming that the cables are of the same length and size, connections are good and the same and the bms measurements are reasonably correct. All four of my JK’s needed tweaking and only one had the amps correct. Do you need to adjust them? It’s probably not necessary if your system connections are good they should still report 99% SOC when full and off a bit anywhere below. I wouldn’t disconnect one battery to try to balance them back. The minute you reconnect they will transfer between each other and be back to the difference. If the difference is a lot there’s going to be a lot of current when you reconnect.

 

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Thanks for your reply Skypower. Batteries are same production line and time and set up in same way with the JK BMS. I will read over your post carefully so I can get a clear view on it.. Your spot on regarding my try to disconnect the one battery...As soon I connected back transfer back started and then back to same as it was more or less.

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Today i have good weather again and was ready for charge back up to 100% or 99% but on 97% all charge stopped so I guess thats a sign that my state of charge is wrong and need to be reset? If so how?

Edi: Let me ad that the other battery show 99% and the stopped to charge in same time

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[Skypower]

Today i have good weather again and was ready for charge back up to 100% or 99% but on 97% all charge stopped so I guess thats a sign that my state of charge is wrong and need to be reset? If so how?

Edi: Let me ad that the other battery show 99% and the stopped to charge in same time

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Very common, it’s nothing you did wrong. If you do nothing it may learn by itself or most likely the SOC DISPLAYED will probably get worse with each cycle, but it will have no effect on the actual capacity, performance or safety features of the bms because there are no settings that rely on SOC. If you wish to correct it and you don’t want to wait to find out, you will need to make some TEMPORARY changes in the app, perhaps a few times for the bms’s to hard learn it.
Here’s how I did it;

JK bms fast(er) SOC learn

I’m reasonably satisfied with my JK’s…now. I thought I had a problem because my third battery commissioning went a little rougher than the first two JK’s. Something was definitely different with the third and newest bms. The first thing that popped up was the yellow flashing “Change password in...

diysolarforum.com

 

[Pink]

Very common, it’s nothing you did wrong. If you do nothing it may learn by itself or most likely the SOC DISPLAYED will probably get worse with each cycle, but it will have no effect on the actual capacity, performance or safety features of the bms because there are no settings that rely on SOC. If you wish to correct it and you don’t want to wait to find out, you will need to make some TEMPORARY changes in the app, perhaps a few times for the bms’s to hard learn it.
Here’s how I did it;

JK bms fast(er) SOC learn

I’m reasonably satisfied with my JK’s…now. I thought I had a problem because my third battery commissioning went a little rougher than the first two JK’s. Something was definitely different with the third and newest bms. The first thing that popped up was the yellow flashing “Change password in...

diysolarforum.com

Thanks Skypower.

Edit: just tested it and it kind of worked. Before I see 150A or so and after temporary adjust over voltage protection now i see 263a of 280a on fully charged.

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Maybe working better than expected Skypower: I calibrated voltage in same time as reset SOC.. And I see now still charging..now on 268 so the 263 was more exact than I understood when i replied.

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