[SilentAttack]

So long story short but still kinda long.. My wife called me a couple weeks ago saying the car had lights that came on and it wouldn't start. She sends pictures of the iDrive and it says Battery charge level low along with braking chassis stabilization malfunction and the gauge cluster had an ABS 4x4 on it. I drove out there hooked up my scanner and nothing so I jump the car and on the way we go.

Fast forward 2 weeks and I keep the car to get a tire balance and rotation done and the same thing happened to me.. I have a portable jumper so jumped the car and on my way I was. I ended up buying a new battery even though my AGM battery is only 3.5 years old as it sounds like the battery. I change the battery and take the core back and ask the guy to test the battery to be sure that was the issue. To my surprise the battery was in near perfect condition... Now is the part where I sit and wonder what the heck is going on, is is a faulty battery that for some reason just drained itself some how or could it be another issue outside of the battery itself?[IMG]undefined[/IMG][IMG]undefined[/IMG]

[blueloco]

Check for codes. Take a look at the IBS system. Use INPA to see what it figured the state of charge and health were and if the new battery 3.5 years ago was "registered" proper and has the correct amp hour rating and battery type. The car must be coded when switching batter sizes and between lead acid and AGM. My car came with a replacement lead acid and was coded for an AGM. Basically killed the lead acid battery by constant undercharging.

[SilentAttack]

Originally Posted by blueloco

Check for codes. Take a look at the IBS system. Use INPA to see what it figured the state of charge and health were and if the new battery 3.5 years ago was "registered" proper and has the correct amp hour rating and battery type. The car must be coded when switching batter sizes and between lead acid and AGM. My car came with a replacement lead acid and was coded for an AGM. Basically killed the lead acid battery by constant undercharging.

thanks for the input but I did have a friend that works on BMWs code the battery along with other things at the same time which all had worked great since the coding was done so I'm in hopes that also went smooth. As for the IBS, I did look into that and it seems if that were the issue the car wouldn't even crank which it did with ease after a quick jump. it's almost like the battery has gone bipolar.

[blueloco]

Originally Posted by SilentAttack

it's almost like the battery has gone bipolar.

All batteries are bipolar. They all have their positives and negatives.

An IBS failure wouldn't necessarily break continuity. It provides information on battery states to determine how much the alternator is charging it. That is on the negative end.

On the positive end there is the disconnect (BST) that apparently can also break. That is part of the SRS system and that would prevent the car from starting.

[John 070]

I have a bit of a mystery myself. My wife has a GM car and it too has intelligence behind charging, and also a voltmeter on the dash.

Knowing this car brand new, you would see that the volts are around 14.25V, then back off to about 13 if say the car ran 2 hours on the highway.

After 4 years we got a Bosch Premium from the Three Stooges (it was rated #1 CR). Prior to the failure, the volts were really high, beyond 16, AND, the trip odometer and mpg and avg mph erased/reset. This was a clue.

This happened only 1 yr. later, again. My plan was to exchange under warranty for free, but I don't want Bosch anymore, so I got a Costco. Using my tester, the Costco had 930 CCA not installed, sweet!!

What I forgot about was that it was about 65F, not 0F.

Then, I test the Bosch, from the terminals under the hood (the battery is not there), and it's 480 CCA! Nice, I am so smart, the battery is bad (read on, WRONG!).

I install the Costco, and test the Bosch out of the car, 900 CCA! wtf

I can't say now why a "bad" battery could pass a load test, there is some other factor, like the resistance etc. Because with the 2nd Bosch battery, the voltmeter never got to 14.25V, let alone 13V. It was always high. The new Costco will drop down to 13V once the car has been on the highway a long time. If anyone could shed light that would be great.

[ctuna]

When you are measuring if the Motor is running you are
measuring the alternator output not the battery.
I don't think its possible for a car battery to measure above
13 volts. And its usually lower as 13 is optimum charge and
what is called a surface charge . As soon as a car is started
with that voltage it will drop to something in the high 12 range
if its good.

Or is there some new kind of battery I am not aware of speced to be a
higher voltage. If so it should say what the range is right on the battery .

Voltage is about the only thing you can test at home without a load tester.
And to use one of those the battery has to be disconnected as far as I know..

[nissubaru]

Every time a thread like this pops up I say to check the grounds! Our batteries are in the trunk so they require GOOD grounds in order to receive the full output from the alternator. I misdiagnosed my alternator as being bad/not charging my battery because I used a grounding point for my multimeter that wasn't well grounded.

Basically if I had used the engine block as the grounding point for the multimeter I would have seen good readings from my alternator. However I instead used one of the bolts for the strut brace which resulted in weak readings. In my defense, I also did the same sort of test on my other car at the time just to make sure I wasn't being an idiot and my alternator test worked perfectly over there. It wasn't until I used another ground point with my multimeter that ended up with perfect readings which told me I was onto something. Replaced the ground with one that was $10 on eBay and I haven't had any issues since.