>>792916>0°Fcorrection, 0°C.
The 18650 cells I use in my equipment that gets deployed in the snow, onboard charger's set to allow charging between 3-42°C. Outside of that range, you risk cell damage/fire. Status including cell voltage can be read wirelessly, so if one unit's low I can dig it up while it's still functioning, throw it in the trailer/truck for a while to warm it up, and let it charge for a few hours.
