The depletion of storage batteries

[tr4s]

I had the RAC come out and jump start the car after I had left it on our trip for two days, and now it's operating well. The rac guy claims that the battery must have drained, but I have no clue whence that drain came from. On the other hand, I did realise that I had left the car unsecured for two days—my wife was not impressed—so I wonder whether it contributed.I switched off the heater fan and went for a run, but the engine on the passenger side still sounded like it was spinning.

[depofly]

Up until this point, did you have any 'Battery Low' warnings?

[Radiantecon]

Under the passenger seat of an L551 vehicle you should find a 48v mild hybrid battery. It uses a dc/dc converter to change the 48v into 12v. If you hear a fan-like noise coming from that direction, it might mean that it has failed and the 12v battery isn't charging.
If your 12v battery is original and old, it's possible that leaving the car "awake" has flattened it. To be honest, I have a strong preference.

[tr4s]

It is an MHEV, and the battery is only three months old.

[spartan]

Good day,

Leaving it unlocked will cause some of the modules to be active, which will gradually deplete the battery.


The battery was practically dead by the time I finished cleaning the car one day since I left it unlocked for much of the time while washing and waxing, etc.