Dead battey

[DamianF]

Morning all

The battery in my 911 is completely flat - I’m trying to start it with a lithium jump starter but it’s showing a reverse polarity indicator even with its cables connected correctly. Checked on another car and the jump starter works fine.

Anyone have any idea what could be going on? Maybe the battery is dead??

Thanks
Damian

[Nine One One]

Have you tried to start the car with the jump starter with the cables actually off the battery?

If the jump starter is showing a wrong polarity, its possible the plates in the battery have buckled and are forming a contact inside the battery. If they are, you need to remove the battery soonest so nothing is damaged?

[redrobin911]

Firstly I think your better off buying a new battery, however I've recovered dead batteries before even with "smart" battery chargers that either show up a "dead" code and then won't charge. What I do is get the dead battery and a good battery connect + to + and - to - then connect the battery charge to either one of the + and -. What happens in laymans terms is that the charger see some voltage so will charge both batteries at the same time. After an hour or so the good battery can be removed and there should be enough charge in the dead batter for the charger to work. I'd then deep cycle charge for 2 / 3 days and see if that recovers it. My 2p worth,.

[gridgway]

Firstly I think your better off buying a new battery

End of. Fools errand to do anything else in my experience!