I am running test with a self-heating battery, and I noticed a certain behaviour when charging at low temperatures, and I am wondering if that could cause a problem down the road.
The battery is at -11°C (below freezing), and when I apply a 1 A charge current, the following happens in the BMS-monitoring app:
My reading of the situation is the following: the charge current is stopped by the BMS, and the heater kicks on, and is turned off right after because the voltage drops. This might be because my charging current is not enough to run the internal heater, but it's a realistic scenario with low solar input int he winter.
My questions are:
The battery is at -11°C (below freezing), and when I apply a 1 A charge current, the following happens in the BMS-monitoring app:
- The BMS accepts the charge current
- A few seconds later, the BMS throws a "Charge undertemp!" and stops the charge (as it should)
- Another second later, the BMS registers a ~100 W load outgoing, and resets the charging alert (allows charging)
- The voltage drops, the outgoing load stops, the cycle repeats at step 1.
My reading of the situation is the following: the charge current is stopped by the BMS, and the heater kicks on, and is turned off right after because the voltage drops. This might be because my charging current is not enough to run the internal heater, but it's a realistic scenario with low solar input int he winter.
My questions are:
- Is it problematic that the BMS allows a small charge current every couple of seconds at this low temperature?
- Will the frequent switching between states cause any problems down the line?