My 745Li will lose power and engine will stop after jumper box removed?

[JaydoggSF]

Hello,

im thinking a bad bad battery or alternator? It has been sitting for 2 months so dos this make sense? I'm not an expert but I know a little about the car. New owner.

Starts right up when the jumper box is connected. No box connected, nothing happens.

Any my help or guidance is much appreciated.

jeff

[Ianmark]

If a battery is not kept charged and allowed to discharge for a couple of months, there is the possibility that it will not accept a charge anymore, or it will not charge up enough to start the car.
Keep the booster on the car after boosting it and let the car run for a few minutes. There really isn't a way to check the alternator if the car will not run, without taking it out of the car and
having it tested somewhere. Do you have a battery charger? If you have one or can borrow one, charge the battery overnight and in the morning you can test the system with a volt meter.

Ian