Dead car battery/jumpstart problem diagnosis

Yes, definitely. 7 years is old for a battery.

Also make sure the clamp that you put on the car body is on bare metal. I’ve had trouble jumping a car before and moving the clamp from a painted piece to bare helped. That said, 7+ years is a pretty good run for a battery. Mine tend to last 5.

Your car , like almost everything else made after 2000 has a constant drain on the battery for the various computers on board. It’s usually small, in the order of milliamps, but it’s there. Infrequent driving, low battery state, and an older battery are all conspiring to kill it. Once a standard car battery drops below 6 V its life is considerably shortened. Lead acid batteries are happiest when they don’t drop below about an 80% charge. In all likelihood you need a new battery, and I would have the charging system tested at your local car parts place. I wouldn’t sweat getting anything like top of the line because your charging system may not properly maintain it. AGM and spiral grid batteries need a different charging profile than the old standard plate batteries; some cars do it right, some don’t. Further, since you don’t drive very often, invest in a battery tender like this one. That’s roughly a $200 all-in fix, assuming your charging system is serviceable. Maintenance is like that old FRAM commercial. “You can pay me now, or you can pay me later”.

TL;DR: Buy a new battery, have the place test your charging system, and buy a battery tender to keep it happy.

Thanks for all the input! Taking it all into account, and since I probably won’t be keeping this car for more than another year, I’m leaning towards just replacing the battery and seeing how it goes, but not necessarily hurrying to replace the car until another problem comes up.

You have some kind of parasitic draw, which can be tricky to diagnose and repair. If you are not interested in trying to find the fault I would go with swapping the batteries. You might consider just keeping the charger hooked up overnight.

Keep the jumper pack charged up and handy������

If you’re only going to keep if for a year, look into getting a used battery. Repair shops or junkyards sell them much cheaper than a new one.

The ‘defective ground’ is more likely to be in the way you connected the negative cable than an actual bad ground. It’s hard to do that effectively on many newer cars if you’re not mechanically inclined. (Connecting directly battery-to-battery is the way to go. I’ve been doing it that way for nearly 60 years in Minnesota, and never had or even heard of anyone affected by the so-called safety risk.)

Do try jumping it for a few minutes before trying to start it* – that might be enough to get you old (and end-of-life) battery to work again. Then you might be able to keep using the old battery until you replace this car. But in that case, I’d buy a battery charger (with trickle-charge circuitry) just to have on hand if this happens again. (And maybe connecting the trickle charger overnight every few nights will prevent this problem.)

*I thought everyone always did this when jump starting a vehicle.

If you have a voltage drain one solution is to simply disconnect a battery cable from the battery when you are not using it. Since you only use the car a couple times a week this is a workable method. Note it means your clock will be at the wrong time.

What your coworker suggested is probably correct.

Most jumper cables people carry will not do a real jump, as in instant, the cables are too thin.
If the set didn’t feel like it weighed 10lbs it was too thin to do an instant jump of a totally drained battery.
It acted how it did because the first attempt to start drained the battery below the gate voltage.
Below that a modern car will react as if there is no voltage.

I doubt you have dark current ( a drain) over the usual amount.

What you have is likely a combination of corroded plates and weak electrolyte. In this case the battery itself kind of shorts out internally and creates it’s own drain.

A long jump, will likely get it started and home.
It needs a new battery.
Unless you’re handed an analyser printout, the batter y was not thoroughly checked in 90 percent of cases.

To check for dark current you can use a $5 multimeter, set it for current, disconnect one battery terminal and touch the battery post and the terminal with it’s leads , you should get a reading around 50-100 mA normally, with a charged battery, key off.

If you replace the battery and this is the case you’re good.

I give you 98 percent likelihood a new battery will be all you need.

For my pontoon boat batteries I use a disconnect switch instead of removing a cable all the time.

A seven year old battery, which has been drained and jumped, and which lives the life described is DEAD.

That’s it.

This is insanity.

Yeah, it’s likely dead.

I was thinking about that ground thing and one of the reasons that people struggle to do when jumping positive to positive, negative to ground is that when you ground the clamp to the engine of the good battery, it HAS to be an unpainted part or the electricity will not flow properly.

Thanks to everyone for their input! Hopefully this saga is at its end.

Took the bus to an auto parts store. Clerk said that, according to their system, it would need a professional install. Something about the car’s computer when a new battery is put in. I called the dealership and spoke to a mechanic, who said that I could probably do it myself, but I might get a bunch of error codes or warning lights, though the vast should still run fine. So I went ahead and got the battery, took the bus home, hauled it to my car, and swapped it. What a pain that was, but I finally got it done. And it’s working fine so far! Hopefully that will continue. Thanks again to everyone!



Car was totally dead this afternoon. No lights, no nothing. Obviously there’s a significant mystery drain on this brand-spankin’ new battery, which worked fine when I drove around for an hour yesterday.

So screw it. I’m taking tomorrow off and we’re going to replace the car. Not gonna spend another grand or so diagnosing it when it already has that emissions thing going on. Gonna recruit a helpful stranger to help me jump it tomorrow morning, then go to the dealers and find a new (used) car. Already identified a handful of promising cars nearby on Goodbye to this Audi. Next car will probably be (based on what we’ve found) a Lexus, Ford Fusion, Nissan Altima, or Toyota Camry (varying from 5 to 10 years old, and all under 100K miles and under $10K).

It is possible you got a defective battery. Or it’s possible you have a problem with your alternator, so that it isn’t keeping your battery charged properly.

But at this point it sounds like you don’t want to mess with it any more.

Since I already suspected a mystery drain on the battery based on the previous battery’s problems, this seems more likely. And a bad alternator wouldn’t drain the battery to the point of being so dead that the lights are dead, as I understand it.

That’s a pretty heavy drain to do that to a fully charged new battery.

I know. It’s hard to imagine what could have sucked a brand new battery totally dry in about 24 hours.

If this were sci-fi, I’d look for some sort of energy-vampire monster lurking in your garage.

Whatever the problem was, it is no longer my problem. Traded it in for an '06 Lexus with low mileage, and before we decided, we took it to a mechanic that gave it a clean bill of health (aside from a couple of cosmetic things). The trade-in value was very low, but we’re relieved that we now have a car that all indications are should be very reliable. Everything I can find, and everyone I have talked to, has indicated that Lexus cars are both very reliable and inexpensive to repair.