Sudden battery failure confirmed -- Misdiagnosis by Digital Battery Analyzer

[jreed]

Just wanted to share a battery failure and misdiagnosis experience yesterday in case a similar situation should happen to anyone else. This might save time and money...

The 2 year old NAPA Group 48 battery failed suddenly yesterday morning on our '97 855 GLT (197k miles).
The symptom was no crank, with dim dash lights. The voltage on the battery terminals was 12.8V before cranking and 5-8V on the terminals while trying to crank. After about a minute the battery voltage would recover to 12.8V.

It took a few extra hours to figure out the cause because of a misdiagnosis at the NAPA parts store, where the counterman used a Solar digital battery analyzer to test the battery -- it passed his test, measuring 650 CCA and had an open circuit voltage of 12.9 V. He said it was my call if I wanted to buy a new battery, but that he couldn't find anything wrong with the old one and would not cover it under warranty.

I put the battery back in the car and checked that the timing belt hadn't slipped, broken or been damaged. Then I jumped the battery from another car and the Volvo cranked, started and ran normally. I drove the Volvo home and parked it. When I tried to start it again, no crank, dim lights. I was 99% sure at this point that the battery was bad.

I was curious why the Solar analyzer had failed to detect the failure. I went to Harbor Freight and bought their old-school analog DC load tester (with 20% off coupon, naturally) and tested the old battery -- the tester reported the battery as Bad, giving about 3-4V under the 100A load test. I bought a new battery at Advance Auto (using their 20% online discount) and tested it with the HF tester and it passed. I put the new battery in the car and it started up and ran normally. Problem solved.

I'd be curious to hear if anybody else has experienced a misdiagnosis before with one of the digital battery analyzers...

I uploaded a short clip showing the load test:


Enjoy!

[BEJinFbk]

I don't know if this applies, but some time ago,
I had an old van with a Diehard that had similar issues.
Within about three days, the nearly new battery died.

The problem turned out to be a crack between the post
and the end plate. Towards the end, you could put a bit
of pressure on the cable while someone else turned the
key and it would start right up. Sears Warranty FTW!

[jreed]

Thanks. I didn't try putting lateral pressure on the posts to see if it would help.
As you say, the old NAPA battery may have had a weak internal connection that increased in resistance only under heavy load.
What surprised me was the "pass" result from the DBA. It made me think the battery might be good and that something else in the car might have been the problem. So, I put the old battery back in and checked components for excessive current draw (pulling the fuel pump relay, tapping the starter motor, verifying the timing belt was intact, testing that the engine crank would rotate, etc). In the end, it turned out to be the battery after all.

[MrAl]

Hi,

I have had problems with Napa batteries that i never had with other batteries, even from WalMart.
I wont buy that brand anymore.

[jreed]

I am with you. This Napa battery was the third replacement battery. The first Napa lasted 1.5 years. The second lasted 4 years. The third (the one described above) lasted 2 years. All three of them failed suddenly.
I decided to switch to a different battery supplier to see if I get better luck.