I'm going to replace my kaput Pb (lead acid) batteries with LiFePO4 soon. One thing that was holding me back was finding a low temperature disconnect to prevent charging ( nd destroying) the batteries below 0 degrees C. The few commercial devices I found seemed pretty expensive and overkill ( I don't need Bluetooth on it thank you very much). Witha temperature sensor, 200A relay, an RC snubber circuit to suppress arcing, and a Zener diode and power resistor to regulate the temperature sensor power voltage this will do the job. And I spent $35 and that is enough to make two units with spare parts left over.