when is the right time to change battery
 

I have 02 3.0, do u think its time to replace my battery or just wait. im thinking to get duralast from autozone, any info please, thanks

I have an '01 3.0 with 123K miles and am still running the original battery.

If it is a matter of "peace of mind", go ahead and do it.

change it under controlled circumstances
 

a battery usually lasts 4 or 5 years. many people get even more. but even if you take the cost of a battery and divide it by 5, it comes to a pretty small amount.
if you change it now, you can look around. maybe try to get a good deal. if you wait until it fails, you may get stranded and have to call AAA which can take an hour or more if it's a busy time. not fun if it's coming out of a restaurant or movie.
my point is that the cost of replacing a battery is less than the inconvenience of it failing at a bad moment.
BTW, i have an '02 3.0i and the OEM battery only lasted 4 years and it was as dead as a doornail.

thanks guys

Battery longevity seems to vary quite a bit - mine was replaced due to failure at about 30K on an 04 4.4. Could have been defective I suppose. I don't think you'd be doing yourself a disservice if you proactively replaced it now at 5 years - may save you a headache down the road as UncleBob said...

so where did you guys get the battery, brandname and cost?

Just replaced mine (02 3.0 w/75K). Went to start it and it was dead. No warning but I knew it was inevitable.

AAA jumped me and I went to Sears on a Saturday (ug). Two hours later and $170 I had a new battery (49).

Interstate battery $135.00 or so

I have an 02 E53 X5 3.0d euro. My battery was replaced late 2006. That is about 5 years. I replaced mine with the dealer's battery - VARTA (oem battery of BMW).

I have replaced a number of batteries to my previous cars and every time battery is getting bad, you can notice that starting the engine gets weaker, that's when you should replace it with new one. Once you notice that battery is getting bad, it takes only couple of weeks or a month when it completely dead.