Shared Knowledge

"BMW X5 - Battery and Alternator"

4 December 2010

Background:

BMW X5, 2000, 4.4L, 143,000 miles

Battery:

Original BMW battery replaced twice in 6 years. Would die suddenly without any warning at all. No longer use BMW batteries.

To ensure X5 electrical does not leak drain battery, have installed a Priority Start. Priority Start disconnects battery from X5 if voltage of battery drops below a set threshold. Priority Start an insurance policy.

Alternator:

Headed out on trip. Got 20 miles from home when alternator light came on suddenly and car began to buck and run rough. Got off Interstate and made it to service station. As I pulled into service station, "Transmission Fail Prog" displayed and car died completely.

Could be battery but more likely alternator. Tried to start car but nothing. Did not want to get car towed 50 miles to dealer and knew service station did not have alternator and that it would take hours for my drained battery to be charged, so bought a new battery and had service station install it.

With fully charged new battery, more or less, in battery box area, started car and drove 20 miles to home. Once home, charged battery again and then drove to dealer.

The BMW X5 uses a water cooled Bosch alternator. Because of the potentially high current loads of power ported cars, more and more, water cooled alternators are being used. By water cooled, I mean alternator has an in and out water hose connected to it.

When told I had "special water cooled alternator" quoted price of $1200 plus install. What choice?

But there is a choice. You can buy a rebuilt Bosch water cooled for the X5 from many places on the Internet for $600 and then have a local repair shop replace it for you.