I set the capacity to 280ah this morning at 100% charge. So that should be sorted now. I think my issue came from the fact I had to swap the BMS as the old one had a fault. When I did that I just swapped out without fully charging/discharging the cells first time round. So it probably messed up the internal settings.
Seplos CAN BUS RS485 48v 200A 8S-16S BMS
- Thread starter Firechief
- Start date
You'll find that it's not charging it at all after that point - I have the same inverter. It just won't discharge until 4.31am. have you logged into Solarman to check the charging/discharge numbers? Looks like the battery charge current drops away
The data shows it drops to 10A, which at ~54V is 500W for almost an hour; where is this 0.5kWh going? Should I set the inverter to stop charging around 95%?
The BMS should turn it off at 100% charge as should the inverter. Perhaps it's going into absorption mode?
98% means 5.6Ah remaining to 100%
It hits 98% an then it keeps charging at 10-5A for an hour without the SoC changing
Something doesn’t add up
Are you getting any alarms on the Seplos?
You might have the same issue I had. The BMS/Sofar doesn't know when your batteries are full and it's assuming they are, but in fact there is still room. You can try what I did. Up the cell capacity to something big like 400Ah and charge for longer. The BMS will cut off the charging. Then at full charge reset the capacity down to 280Ah. That worked for me anyway as then it discharged down and recharged normally
I have just changed from 280Ah to 400Ah and the SoC has dropped from 67% to 46%; so I think it’s based on the remaining capacity
I’ll see what happens when it charges tonight
The only problem is that I don’t have a way to full discharge it, my inverter only discharges to 10%.
No, the invertor is seeing the same SoC that the bms report
The moment I faked the capacity from 280Ah to 400Ah, the SoC changed from 66% to 46% because it retained the remaining capacity information (186Ah)
186/280 = 66%
186/400 = 46%
So when the inverter cuts off at 10% that would be with 10% of 400Ah remaining, which is 40Ah
In reality this will be 40/280 = 14%
When low voltage cut off happens the bms and inverter will think it’s at 10% but in reality it’s 14%
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Once you fully charge the battery the SOC will be reset to 100%. This is how the BMS calibrates the full capacity point. Then after 280Ah discharge, it will be ~30%, but the battery will be empty.
Once the battery gets empty the BMS will calculate the actual capacity and reset the 0% SOC point.
Or at least this is what I expect. The expectations are based on the official documentation.
Once the battery gets empty the BMS will calculate the actual capacity and reset the 0% SOC point.
Or at least this is what I expect. The expectations are based on the official documentation.
shavermcspud
Solar Enthusiast
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- Mar 12, 2020
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- 581
You are changing the wrong parameter, set the capacity as 280Ah if that's what you have, then change the SOC to 280Ah and let it discharge, as stated above, once its empty the LV disconnect will kick in, then give a full charge and the top end will be calibrated too.
It will never hit LV disconnect unless I make the inverter think there is a lot more capacity
duyvietstar
New Member
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- Jun 11, 2021
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- 16
What kind of inverter do you have? why do you change battery type to lead acid? and aftter that you set voltgae charge and discharge, i think your battery bank will discharge to 0%
Sofar ME3000SP
Still waiting to reach 54.8V which is my ‘total overvoltage protection’
I did hit ‘total pressure high pressure alarm’ which I’ve set to 54.68V and it doesn suddenly drop to 9A at that moment, it drops progressively and it’s about 9A when it hits that voltage (it was already dropping before and it keeps dropping afterwards)
63mV deltaV at this point
Edit
The SoC has just jumped to 90%
Second edit:
It was charging at less than 1A when it stopped charging before reaching total voltage overprotection (54.8V)
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