Re:Heat (Score 1)

All major players in the power tool industry now have Lithium Ion 18V and 36V options. The increased high power has enabled them to come out with cordless varieties of some tools for the first time.

As far as heat, the batteries will not explode if left in a car. Cobalt Oxide batteries go into thermal runaway at about 190C - well over the boiling point of water. Other chemistries such as Li-manganese cathodes go into thermal runaway at 250C. They all have issues at low temperatures and cannot take or release a full charge below 0C. However, it is relatively straightforward to use a trickle charge to slowly heat up the battery above 0C and then get full power - takes about 5 minutes extra at the most.