A8Pete

Looks like I made a mistake in my post too. I meant to say that I connected the negative to the hexagon shaped post above the negative terminal. I'm hoping a few ore hours will get it up to 100%. Then I agree, a discharge under load will be a much better test. Its a 95Amphour batter, so I need something heavy duty to unload it.

mishar

Shops have gauge with resistance that draws certain amperage (different according the battery size). They connect it for a few seconds and measure voltage. I believe it should stay above 1.69 V, but they should know.

A8Pete

Thanks Mishar - Im going to give it another 9 hour trickle session today and see if it goes from 60% to 100%. Then I can see if it holds. Fingers crossed.

MP4.2+6.0

Thinking about this, go back to the most simple battery diagnostic: age. How old is it? If you don't know personally, there is likely a date stamp for either manufacturing date (OE style) or for install date--your typical store counter stuff. As a 2004, your car could be ready for its third + battery. If by chance it is the original, forget it and change out.

Simplifying, if battery is more than about 3 years old and I have charging issues, it gets changed out by the second time it lets me down. Diagnostics time and breakdown risk exceeds value by then in my mind. And, assuming you are anywhere in the Northern Hemisphere, this is the easy time of year on batteries. You don't want to be cranking and starting a car with a weak battery in the cold, especially a diesel.

To recent posts, you should probably see 13 V plus on a fresh battery, but as stated that is a no load test. Even w/ no load though, if you just leave it sit and then voltage drops off meaningfully after a day, it's shot.

A8Pete

Very sensible advice. I'll go and look for a data sticker. Its the same battery that came with the car and I have had it 2 years. So probably looking like time for a new one.