Chargers do get warm, and my chargers for other things, like my car, or larger
batteries, actually have cooling fans. The caps and resistors in the charger do get warm, but not hot.
If it is overly hot, like burning your hand or melting the charger housing, then I would stay away. But if just feels warm, but the plastic is ok, and the heat is being properly vented, you should be ok. Even check the wire to your electrical outlet. That shouldn't be warm at all.
Also,
batteries should not get hot at all. They may get slightly warm at the worst, but charging at a slow rate shouldn't create much, if any, heat for the
batteries.