I have two 200AH, 12 volt no-name LiFePO4 batteries in parallel and a BMV-712 monitoring them. I have adjusted the shunt zero settings on installation. The synchronizations are happening as expected so those settings are at least close.
My issue is that if I don't charge to 100% SOC for a while, the BMV is accumulating error. The monitor says the system is at 100% quite some time before it reaches the cutoff voltage.
Each time it does reach 100%, I have been adjusting the Charge Efficiency Factor to try to get the BMV to track the batteries more closely. I started at 99% and have been dropping it 2% each time. I am now down to 89% and may have to go a little further.
I understood that LiFePO4 batteries were more efficient than this. Am I doing something wrong? I see that there are rather large balancing resistors on the internal BMS units - perhaps 2 watts. Could this inefficiency be due to balancing? The batteries are staying pretty cool - about 20C so I'm doubting that this is the issue.
I am charging the bank with about 50 amps, so a very low C rating of about 0.12C. My discharge currents are also relatively low. I have the Peukerts Exponent set to 1.05 as advised.
Thanks in advance for any help.