The Charging Lapotron Crystal is an upgrade of the Charging Energy Crystal added by IndustrialCraft 2. It acts much like an Lapotron Crystal, although it can store more energy. Secondly, having one in your inventory will automatically charge any other (LV-EV) EU-powered tools or batteries in your inventory, similar to an Energypack. This is particularly usefully when compared to the Energypack, as it frees an armor slot for a Jetpack or something more protective, and additional it is EV as the Energypack is just HV.
The Charging Lapotron Crystal originally was a part of Aroma1997's Portable Recharger mod. However, it was annexed into IndustrialCraft when Aroma joined the IndustrialCraft 2 Dev Team.