The act of connecting an 8530 G2 or 8525 G2 (85xx) to an external 12 V battery as an external power source is not a simple act of plug and run. There are details that need be considered so that the usage does not harm either the computer or battery. For example, overuse (e.g. deep discharge) of the battery may reduce the life of the battery.
We are working on further documentation to help communicate issues that should be taken into consideration.