You need an aftermarket power socket wired directly to the battery. Preferably on a switched relay. You can 'switch on' the relay with a feed spliced into your power socket feed but you MUST remove all accessories if it goes in for programming or youll mess up your GM module.
You can then test the charging input to the battery whilst your mac is charging. As long as its over 14v it wont drain the battery whilst charging.
Im a BMW dealer Tech.
__________________
Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.
|