I am trying to diagnose what I think is a failed battery (under warranty) but it passes a battery test.

In days of yore if a battery lost a cell it dropped from a notional 12.0v to somewhere under 11v when stored after a full charge. I.e. if you drove the battery to fully charged (around 13.5v) and then disconnected the charger, pretty quickly the voltage drops below 11.5v, maybe in a day or so.

These latest tech batteries run at higher voltages (I have a new 86-7MF). It is under charged below 12.5v and is fully charged around 14.3v. It should show around 12.8v in store.

What is happening is it charges (out of car) to 14.3v too quickly (in say 24h, my high tech charger can only deliver 0.5a) and then over 48 hours drops to 12.1v. However, it has managed to pass a battery test check, I suspect because it was just over the 12.5v at the time. (And you can't test a battery with a voltage below 12.5v, the tester will charge it first.)

My conclusion is that the base cell voltage in these latest tech batteries is around 0.1v higher than before, which with 8 cells gives a +0.8v effect and as a result is confusing some battery testers (cells used to be 1.5v each). Makes diagnosing a bad battery tricky too. Keeps coming back no fault found.

The effect on the car is curious in the least. It clearly isn't happy and is shutting off too fast, the door locks are playing around, all sorts of odd behavior. If I get another battery and use booster leads to connect the two in parallel, all the problems go away. (Except, of course, I can't exactly drive anywhere!). The trunk lid sticks down too. (Motor runs but latch stays latched)

Anyone else know about this stuff?

What sort of battery test check does it pass? Where did you purchase the new battery, and how old is it? Over the years I've experienced two cases of battery "infant mortality" and been told that while most battery failures occur after the end of the warranty period, the next most likely time to fail is within the first couple of months of use.

Were it mine, I'd take the battery to Advance, Autozone, and at least one other auto parts store for testing. (maybe Sears, but don't consider that a recommendation).

What sort of battery test check does it pass? Where did you purchase the new battery, and how old is it? Over the years I've experienced two cases of battery "infant mortality" and been told that while most battery failures occur after the end of the warranty period, the next most likely time to fail is within the first couple of months of use.

Were it mine, I'd take the battery to Advance, Autozone, and at least one other auto parts store for testing. (maybe Sears, but don't consider that a recommendation).

The battery is about 2 mo old (that is, I've had it about that long). It has been tested both by my tester and by a 3rd party tester from an auto parts store. Their tester requires entry of the battery's capacity as part of its test which takes a few seconds. The snag is proving that it is defective. I'm sure it is, but how do I prove it? My tester sometimes fails it but that doesn't count. It is entirely possible the battery was defective from new but didn't show up until the current cold weather. The alternative to the battery being defective is the XLR has too big of a parasitic load when quiescent, which would take a great deal of hunting down.

My question though is if anyone has knowledge of the latest technology batteries and what their failure modes look like?

Finding an alternative battery to the Delco one is also tricky, there is not much room and that battery packs a big punch for its size. This is not the only 'new' battery that has been defective I might add.

I just had my 2008 XLR-V battery go out. It was a dead cell.

The GM replacement had more cold cranking amps than the original one.

What about a load test?? It should turn up any weak cells in the battery fairly quickly.

I just had my 2008 XLR-V battery go out. It was a dead cell.

The GM replacement had more cold cranking amps than the original one.

What about a load test?? It should turn up any weak cells in the battery fairly quickly.

I am told that the test carried out was indeed a load test, though it didn't take the form I am used to. The old tester was a big resistor pack, this tool is a Bosch device that apparently can work it all out with a lesser load test, it just needs to be told the cranking amp capacity of the battery.

The alternative option I have to face up to is a circuit pulling excessive load.

I have put a separate battery in in parallel with the main one, and have a data logger connected to the voltage. Right now the main battery is disconnected, so I am recording the voltage of my big spare battery (one I know to be in good condition). I'll see how it goes. I'll also figure out a way of running a current draw test with the data logger, but that is trickier to set up. (A matter of too many cables lying around with huge currents available)

As I was curious about this problem, I talked to a battery specialist to find out more.

The problem is that the battery has (almost certainly) become sulphated.

Sulfation occurs when a battery is stored at too low a state of charge. Modern batteries should show a voltage of between 12.6 and 12.8 volts when in store.

Below 12.5v the battery is susceptible to sulfation and by 12.3v (half charge) the process is likely.

To maintain a stored battery above 12.6v requires it to be charged about once per month. This assumes it is not connected to anything. Apparently Delco batteries are generally considered to hold their charge better than other brands. Batteries fitted to a car, especially one such as our XLRs with a lot of electronics, will require regular re-charging, i.e. regular (weekly) use, or a battery tender.

Sulfation cannot be corrected. It reduces the capacity of the battery, so while the battery can show approximately correct voltages, it discharges far too quickly, as only part of the plates are functioning. It is entirely possible for a sulfated battery to pass load and other tests. Evaluation requires a discharge/charge plot, which explains why both my battery tender and my XLR (odometer does not display on switch off) can identify a problem but a battery test does not.

Re the test, it worked fine, my other battery behaved nominally.

BTW, the correct battery has a rated 640 CCAs and is an 86-7MF (or 86-7YR).

FWIW:

I just pulled my service invoice for my battery replacement on my XLR-V.

It showed the following:

No Crank--Had to be jump started
Battery failed load test 10.36 V 3CCA.
Replace Battery Test Code 001NN-RT-B3

Battery Number 85H7YR

(odometer does not display on switch off)

This piqued my interest as I am still struggling with starting issues. I have noticed that occasionally upon shutoff the odometer display stays lit; other times it does not. When it does, I will typically hit the switch two more times. One to turn on accessory mode and the second will turn off everything. Is there a connection between this and known parasitic draw issues? My XLR is an '05.

BTW and for your future reference - the Optima Redtop (34/78) and YellowTop (D34/78) fit very nicely in our little cars, regardless of the manufacturer's cross reference material. :cool

This piqued my interest as I am still struggling with starting issues. I have noticed that occasionally upon shutoff the odometer display stays lit; other times it does not. When it does, I will typically hit the switch two more times. One to turn on accessory mode and the second will turn off everything. Is there a connection between this and known parasitic draw issues? My XLR is an '05.

BTW and for your future reference - the Optima Redtop (34/78) and YellowTop (D34/78) fit very nicely in our little cars, regardless of the manufacturer's cross reference material. :cool

That is interesting. When I looked at Optima batteries, the bigger problem was that the terminals were further from the corners than 'normal' and the rigid fittings on the cable ends of my '04 XLR would not reach. IIRC the Yellow top is better as it copes with the parasitic drain better than the red top. The min spec Delco is around 550CCAs too. I'll have to check that (the 6YR) (the 7YR is 640 CCAs).

The behavior of the odometer suggests battery problems (it should stay lit). Mine is OK after a long run and then very quickly it reverts. A fully charged normal battery is well over 13 volts, engine stopped. 13.5v is top end fully charged. Anything below 12.3v is a major problem, below 12.5v is a problem, above 12.8v will be considered fully charged though in fact it will go a bit further. You need a decent voltmeter to check this, don't use the in-car display. Check using the actual battery terminals (instead of the wiring, though of course, it should be the same!).

That is interesting. When I looked at Optima batteries, the bigger problem was that the terminals were further from the corners than 'normal' and the rigid fittings on the cable ends of my '04 XLR would not reach. IIRC the Yellow top is better as it copes with the parasitic drain better than the red top. The min spec Delco is around 550CCAs too. I'll have to check that (the 6YR) (the 7YR is 640 CCAs).

The behavior of the odometer suggests battery problems (it should stay lit). Mine is OK after a long run and then very quickly it reverts. A fully charged normal battery is well over 13 volts, engine stopped. 13.5v is top end fully charged. Anything below 12.3v is a major problem, below 12.5v is a problem, above 12.8v will be considered fully charged though in fact it will go a bit further. You need a decent voltmeter to check this, don't use the in-car display. Check using the actual battery terminals (instead of the wiring, though of course, it should be the same!).

There must be a parasitic drain on the battery. My girlfriend just bought an '05, and the PO had replaced the battery several times. I did notice that the interior lights were staying on, because she had pressed the interior light switch right under the DIC switch. I'm just wondering if that could be part of the problem I'm reading about that so many are having with batteries that die so soon.

Yea the interior light and the map lights (under the mirror) will cause a constant drain on the battery which could lead ultimitely to battery failure.

The dealer should be able to tell you if there is a drain on your electrical system after you have gone through the obvious item check list.

Please let us know how this comes out.

Yea the interior light and the map lights (under the mirror) will cause a constant drain on the battery which could lead ultimitely to battery failure.

The dealer should be able to tell you if there is a drain on your electrical system after you have gone through the obvious item check list.

Please let us know how this comes out.

We're going to monitor it. She likes to show all her friends how the top works....but I have been reminding her to have the motor running when doing so, so the battery doesn't run down.:lol

You are correct. Operating the top without the motor running is a HUGH NO, NO. Many, many electrical problems were resolved after ths basic issue was discovered.

Lets see what the electric test shows.

Yea the interior light and the map lights (under the mirror) will cause a constant drain on the battery which could lead ultimitely to battery failure.

The dealer should be able to tell you if there is a drain on your electrical system after you have gone through the obvious item check list.

Please let us know how this comes out.

I thought those were turned off anyways if you left them on, after 20 mins or so? Anyone tried this to find out?

You're right. RAP is supposed to de-energize all lighting, and infotainment circuits 20 minutes after ignition cut-off.

The parasitic drain on the battery is as-designed. The RCDLR module has a small amount of power applied to detect fob proximity after ignition shut-down. --Another good reason for a battery tender/minder during sustained storage. On earlier models, the amount of RCDLR draw was higher, and was fixed with a software patch. It's prudent to ensure your software is up to date anytime you take your vehicle in for servicing to ensure the latest fixes are incorporated.

CC :seeya

You're right. RAP is supposed to de-energize all lighting, and infotainment circuits 20 minutes after ignition cut-off.

The parasitic drain on the battery is as-designed. The RCDLR module has a small amount of power applied to detect fob proximity after ignition shut-down. --Another good reason for a battery tender/minder during sustained storage. On earlier models, the amount of RCDLR draw was higher, and was fixed with a software patch. It's prudent to ensure your software is up to date anytime you take your vehicle in for servicing to ensure the latest fixes are incorporated.

CC :seeya

Is the a charge for the up-date of software?

If you're out of warranty, yes. You would pay for the labor to have a tech connect a Tech 2 (GM scan tool) and download the latest software into the module of interest.

CC :cheers

Is the a charge for the up-date of software?

We may need to do this. Girlfriend has been driving at least once a week, but on Sunday, she found the battery was dead. The battery is only a few months old. We are now familiar with the procedures to open up the car when the battery is dead :).

We may need to do this. Girlfriend has been driving at least once a week, but on Sunday, she found the battery was dead. The battery is only a few months old. We are now familiar with the procedures to open up the car when the battery is dead :).

Are you (is she) driving enough fully to recharge the battery? These high tech batteries take a long while to charge up fully and also in above freezing weather (and a few other things) it would appear that the XLR does not attempt a full recharge, I assume in order to improve economy. However, as it does not have the current detection circuits being fitted now, I suspect it could be more vulnerable to not charging the battery as much as it should or could.

Be aware too that the OEM batteries pack a considerable punch into a small volume and I feel that makes them more vulnerable to problems once they have become deep discharged, even once.

Moral, use a good quality battery tender if you are at all in doubt. I connect up from time to time, if I have only driven a few miles in a week.