The Charging RE Battery is a rechargable battery added by IndustrialCraft 2. It acts much like a RE-Battery, although it can store more energy. Secondly, having one in your inventory will automatically charge any other (LV) EU-powered tools or batteries in your inventory, similar to a BatPack. This is particularly usefully when compared to the BatPack, as it frees an armor slot for a Jetpack or something more protective.
A BatPack cannot charge a Charging RE Battery. Likewise, a Charging RE Battery cannot charge a BatPack.
The Charging RE Battery originally was a part of Aroma1997's Portable Recharger mod. However, it was annexed into IndustrialCraft when Aroma joined the IndustrialCraft 2 Dev Team.