The unified charge pack was an energy pack created by Ultima Engineering in the 2430s. They were cheap, provided a substantial power output that was fairly reliable. Their power rating is enough to power as much biotech as someone would be willing to implant for about a year. An entire personal area network for a month. Or a typical energy discharge weapon for a few thousand blasts.
Ultima Engineering phased them out in 2441 in favor of the demacron power pack (DPP). Officially, Ultima Corporation says that this was due to a weakness in the earlier design not quite being stable enough for the newer technologies. While everyone agrees that the power stability was substantially improved in the DPP, most people realize that the real reason Ultima phased them out, was because in 2440 the Crossbones Exchange discovered how to perfectly reproduce them substantially cheaper than Ultima could, so their sales dropped.