Picked up a 200Ah Fogstar Drift a few months back for the Transit build. Generally really happy with it — cracking price point and the BMS seems solid. But now we're into winter I'm noticing the cells drifting out of balance more noticeably when charging from cold, say below 5°C. Top cell hits 3.45V and the BMS trips before the others have caught up properly. Ends up sitting at maybe 85–90% usable rather than a proper full charge.
Running a Victron SmartSolar MPPT 100/30 with a temperature sensor on the battery. I've dropped the absorption voltage down to 14.2V from 14.4V to try and ease it off a bit, which has helped marginally. The charge profile is set to LiFePO4 preset with tail current at 2A. Not sure if the issue is the Victron config, the BMS low-temp protection kicking in, or just normal LiFePO4 behaviour in a cold van.
Has anyone else found a voltage or tail current tweak that keeps the Drift happier in winter? Or is this just a case of insulating the battery box better and accepting reduced capacity until the ambient rises? The van sleeps in the driveway overnight so it genuinely does get cold before I set off in the morning.
