Battery Voltage
 

Out of curiosity I checked the original battery in my '04 X5 3.0l, which after 6+ years has never acted up. She had been sitting idle in the garage for the past 2 to 3 weeks

Inspected the hydrometer which showed a "black" eye, indicating inadequate charge. Performed Bentley's open-circuit voltage test which showed 11.9v, indicating below 25% charged.

So what the heck, I pulled it and set it on a 12v 6amp battery charger for about 1.5 hours until fully charged. Retest showed 12.5v.

Ran her about the local roads for 1/2 hour - same voltage. Restest after 24hr idle - 12.3v, which Bentley sez is 25-75% charged.

Voltage test with engine running - 13.6v.

Not fretting, but wondering whether this battery still sounds reasonably healthy in spite of its age?

My X is still new to me, but the last battery i replaced was from an E46 and it made 10years. So it pays to buy original BmW batteries which made me decide to pony up the $60 difference from a generic brand

The voltage tests are fine, but for a more complete picture you would need to load test it and see what it holds. You need a tester for that.

At six years, it has provided you the service it was designed for. You may get a year or so more out of it, but at this point it comes down to deciding the value of xx more months, vs the inconvenience of it failing when you least expect it. If you carry jumper cables, and can always get a jump when it goes, and you are the only driver, it may make sense to run it out. On the other hand, if another family member may be driving it, or you depend on the vehicle and don't want to take a chance of getting stranded, it is usually good policy to replace it proactively around this age. I would.

Don't rely on the indicator eye in the battery, it means very little.

And idling it for 24 hours to recharge the battery isn't good for the vehicle at all.

Good fback jcl - thx. btw, i meant to say that it sat in the garage for 24 hrs overnight, not at idle - my bad.

I know this is an old thread but according to the BMW TIS tech data, the constant regulating voltage should be 14.3v. Im guessing this is with the car running, your voltage regulator should be kicking this out. Hope this helps anyone