The Lion battery in the Treo hates two things. 1. High heat.2. draining to low.

The Treo has a protection circuit built in to prevent the battery from getting to hot. I get the warning message alot in the winter months when charging in the car with the Treo in the wind shield mount by the defroster duct. Message says temp to high and the charging and back light stop untill it cools down.
Lion batteries prefer to be charged a little bit frequently vs deep drain and long charge, again due partly to heating of the cells.