Hi there! How do I check the battery strength on my 2009 528i ?
You need a voltmeter or multi-meter and you can probe the positive and negative connections right on the battery access through a panel in the trunk or the connectors under the hood on the passenger side. Check the owners manual for the exact locations. You're looking for 12.3V or more with the engine off and 14.5V with the engine on, which tells you the alternator is charging the battery properly.
But you need a load meter to check cranking amps. Thats where the juice is. I replaced my battery a month ago, it showed 12.5V but the cranking amps were not even in the ball park.
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