Alternator & ChargingDiagnostic helpCommunity Starter

2020 BMW M2 — battery dies after the car sits for a weekend

QuietDaily835Community StarterJan 29, 20262020 BMW M2 CompetitionHouston

2020 BMW M2 Competition, about 55,500 miles. Battery passes a quick test and charging voltage looks normal, but after two or three days parked the car sometimes will not crank. What is the cleanest parasitic-draw test on a modern car that takes time to go to sleep? Mostly looking for the right next step.

1 replies

RotorOwner247Community StarterCommunity StarterJan 30, 2026permalink

I'd want a measurement, not a hunch. Write temp, speed, and in-gear vs coast when the 2020 BMW M2 does it — then decide on parts. Don't erase codes until someone who can help has seen them. Keep sale price, fees, and rate as three different conversations. Heat soak after errands is the other window.

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