So I've got a 2007 Z4 3.0 Coupe. All has been fine with the car except a persisting but infrequent flat battery issue.
It has been flat in the morning 4 times in the space of 8 months, for no immediately apparent reason.
The car is mainly a weekend car - which might lead you to conclude it is not charging enough on short journeys, but on the days it has been flat, I've always driven a huge amount in the day preceding it - typically 100-200 miles. And most recent occasion I completed a 250 mile round trip, but the next morning it was flat. Enough to operate the central locking but not to crank the engine.
This leads me to conclude something is triggering excess battery drain on long journeys, either an electrical drain, or an intermittent alternator related fault.
Troubleshooting steps:
1. Replaced original bmw battery with a Bosch S5 and then a Bosch S6. Problem has persisted since.
2. Checked for drain on each circuit by removing every fuse with a voltmeter attached.
3. Twice tested the alternator.
4. Double, triple, quadruple-checked for anything left switched on!
Does anyone have any suggestions or should I just throw money at a new alternator and hope the problem is solved??!
It has been flat in the morning 4 times in the space of 8 months, for no immediately apparent reason.
The car is mainly a weekend car - which might lead you to conclude it is not charging enough on short journeys, but on the days it has been flat, I've always driven a huge amount in the day preceding it - typically 100-200 miles. And most recent occasion I completed a 250 mile round trip, but the next morning it was flat. Enough to operate the central locking but not to crank the engine.
This leads me to conclude something is triggering excess battery drain on long journeys, either an electrical drain, or an intermittent alternator related fault.
Troubleshooting steps:
1. Replaced original bmw battery with a Bosch S5 and then a Bosch S6. Problem has persisted since.
2. Checked for drain on each circuit by removing every fuse with a voltmeter attached.
3. Twice tested the alternator.
4. Double, triple, quadruple-checked for anything left switched on!
Does anyone have any suggestions or should I just throw money at a new alternator and hope the problem is solved??!
