My daughter was moving Monday and yesterday. Monday she parked and left her flashers on for about 1 hour, the car would not restart. On a jump it started, then restarted after that with a still warm engine.

It sat out for 24 hours and would not restart even on a jump. It had sat out in -10 or so temperatures.

I had the core tested at Autozone. They said it came out as 12.9 volts and half the rated amps. That battery was made in 2010.
What causes that?
Is this what you would expect?
2005 Jetta 2 liter

Typical.
I run an auto repair shop. We replace a lot of batteries that are three to four years old.
Modern cars have so much on board electronics that the batteries are constantly being stressed.

What brand of battery was it?

Sometimes a battery will not recover (or not fully) from being run down. Add temperatures that sap power from all batteries, and a bit of age on the battery, and this can happen. It also sounds like the battery was not fully recharged after having been run down.

I would be inclined to ask for an adjustment and replace it. They may want to charge it fully and then test it first before they will declare it failed.

When I replace a battery, I usually go for the highest CCA rating I can find that fits the car. That way, if it's only producing a percentage, maybe there is enough margin to keep me going.

Might not hurt to test the charging system on the car.
Check the battery cables and terminals for corrosion.
Battery dealers love cold weather, if there is the slightest thing wrong with your batter, it will show up the first time in the winter when the temps get really cold.

Ditto on it not getting fully recharged.

Yes. Although you don't actually say so, I'm guessing that the battery had been used in the car for three years.

I make it a hard and fast rule to buy 60-month batteries and replace them at 36 months regardless of how they test.

My previous 60-month battery started failing at 24 months and was replaced free of charge by the dealer where I'd bought it. Even my hard and fast rule isn't perfect.

Just a gentle reminder to all: it is important to remember that battery is pronounced with two syllables.

batteries are lasting longer than they ever have with new technology.............your battery being in a -10 weather and being drained down created your problem if you still have the battery try charging it for several hours and have it re tested

If it tested at half the rated amps your better off getting a new one. Like was said before, once they run down to a very low state, they are very difficult to recover fully. I use to work 100's of these types of batteries on a weekly basis so i've got a bit of experience with them. I've seen some lead acid batteries go for 10 years and I've seen somce last 6 months, the key to making them last is to keep them clean and charged. I am assuming this is a maintenance free battery?

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This.

Also keep in mind that cold temps are very hard on batteries, especially when not fully charged.

It sounds like the beginning of the end for that battery.

In one form or another, resistance is usually the problem.

Batteries have internal resistance. That increases over time.

Very often, it's a problem with resistance in the battery post connector. The starter wants about 200 amps. If you have .05 ohms of resistance in the connector, you're not going get the current you need.

.05 ohms is too little to measure with a conventional ohmmeter, but you can simply turn the headlights on and measure the voltage drop from battery post to clamp on both the positive and negative battery posts. Anything more than about 10 millivolts (resistance = voltage/current) indicates too much resistance.

Similarly, it is helpful to put the voltmeter probes directly on the battery posts and turn the headlights on. If the post voltage drops too much when you turn the headlights on, you have a problem with internal resistance in the battery. Could be low fluid, could be that the battery is not fully charged, or a couple of other things.

One full discharge of a car battery can reduce its cranking capacity by 20%, forever.

As the temperatures get colder, the internal resistance of the battery goes up. So in cold temperatures, all those little sources of resistance combine to prevent the engine from turning over. Well, that, plus the fact that the engine is harder to turn in cold weather.

Thanks for the awesome post, denton!

Well, it was dead and daddy is not going to have his 21 year old daughter going around like that. It started fine this morning after soaking in 0 degree cold all night. I shelled out the big dollars for the best they had, which was the only one they had for that car.

It was $155 and I had no choice at the time. Money well spent for my peace of mind. Wish she would move home. I understand she wants to be one her own, but I worry about my baby girl. And yes, I am the overprotective type.

Good move.

Batteries are cheap and peace of mind is worth a whole bunch.

do u plug in the car at the colder temps? I have a 8oomA and 2amp trickle chargers on all my stuff

I change my batteries every 3 yrs regardless.

I personally only use American made 6-7yr Delco batteries, not the foreign manufactured items. There is a difference.

$155 today installed is a very good price.

I am 45 yrs in the auto repair business & owner for 35.

-Ken

Any lead acid battery that is completely discharged takes a hit, and will never come back to its full capacity. I have no idea what the chemistry is. We have some lead/acid camcorder batteries that we seldom use, but we need to get them on a charger about monthly. Forget for a couple months and they're toast.

Sulfuric acid and distilled water. The reason you have to charge them regularly is because the sulfuric acid is resting in the plates inside your battery. Charging the battery releases the sulfuric acid back into the electrolyte. If you find your battery getting hot during charging, chances are good that the eletrolyte is getting low inside the battery.

What Denton said. Battery internal resistance rises as the battery ages and a deep discharge seems to add more (for a non-deep discharge battery). Sometimes you can recover capacity by putting a battery on an automatic charger for 24-48 hours if you do it right away. Haven't read a good explanation for this but suspect it has something to do with plate sulfation. Leave it sit discharged and it's lost.

There's another hint in what Denton said. Batteries loose capacity the colder they get. Putting them on a charger warms the battery from the inside out restoring that capacity loss quickly, faster than a battery blanket or heat plate. More than once I've put a cold, low capacity battery on the charger for 10 minutes or so and got a quick start.

And most batteries start failing in the summer and are found when it gets cold.

If it was my daughter's car a new one would go in no question.

I know how he feels about his daughter being away.

On a micro level, the surface of battery plates is porous. This gives the plate much more surface area than a truly flat surface. As the battery is discharged and charged, new lead is plated onto the surface. This tends to reduce the porosity and the effective surface area. So you get less cranking capacity.

Deep cycle batteries are made with more plate mass. Cranking batteries are made with more plate surface area.

Being manufactured by Interstate.

The peace of mind is worth so much more than $155. My daughter and I did the same thing before she went back to college last fall.


Also, when a Pb-acid battery gets discharged (nearly) completely, a cell or two can get a reverse charge which increases internal resistance and greatly limits the reserve CCA. You might get a starter to bump a few times and then the battery dies

Odyssey

I have 3, one in my Polaris Ranger I installed in 2006....you read that right.

2 more in my boat for trolling motor. Pricey, yes. But you won't worry about that battery for 7-12 years.