I could be wrong but I believe the problem comes in when you try to charge them in sub freezing temps when the internal battery temperature is also below freezing. As long as the internal battery temperature stays above freezing no problem. The damage comes from trying to charge sub-freez temperature battery.
Most if not all LION dedicated chargers will not charge a battery that is too hot or too cold to prevent damage or fire. IIRC.
Last edited by snrub; 02/05/19 02:18 PM.
