Dead car battery/jumpstart problem diagnosis

Car is an '04 Audi A6. I go for short drives (grocery store, errands, etc.) about twice a week – maybe ten miles a week on average. Both my wife and I use public transportation for our commutes to work.

About 6 weeks ago, I went into the garage and my car wouldn’t start. The lights came on, though they were a bit dim, but it wouldn’t start at all. Luckily, the maintenance guy in my building was able to drive his truck over and jump start it – and the problem seemed to be over. I was taking my car into the dealer’s shop the next day for another minor problem, so I asked them to look over the battery and electrical system to see if anything was wrong. They looked at it and said they couldn’t find anything wrong with the battery, or anything else that would explain why it had been dead.

So then the car worked fine for the last 6 weeks. No problems starting it up. But yesterday after work, I was going to go pick up my wife, and it wouldn’t start. And this time it was totally dead – no lights, automatic door locks didn’t work, nothing. I had to use the key to open the door – the fob wouldn’t work. There was someone else going to their car in the garage and I asked them to help me jump it. First, I did the jump connection like I read was safe – negative connection (or maybe positive, don’t recall exactly – whatever google told me to do) on the cables to the dead car goes to the engine body, rather than the direct terminal of the battery (with all the other cable connections on the appropriate battery terminals). Didn’t work – no lights, nothing. Then I did the unsafe connection – negative connection of the cables directly on the negative terminal of the dead battery, so a direct connection between the two batteries. This time, the lights came on, door locks started working, etc… but the car still wouldn’t start (didn’t even make the starting noise – just dead, and the lights went out again). And when I disconnected and reconnected, nothing – no lights or anything. So I gave up for the day, and my wife had to walk home.

The car is old and has a few other recurring problems, and I don’t plan to take it into the shop for any extensive work any more. My current assumption is that the battery is totally dead to the point that it won’t take a jump, and I’m planning to walk to a nearby hardware store, buy a car battery, and swap it out. But I assume I still have a slow electrical drain somewhere in the system, so I might buy a second battery, a home trickle charger, and swap them out every few weeks whenever one dies.

But I’m not a car guy by any means, so my assumptions could be wrong. Am I correctly diagnosing the problem? Is my plan reasonable, since I don’t want to do any extensive work?

If the dealer’s shop tested the battery then why would the replacing the battery do any good? [Note lots of places which sell batteries will test them.]

I don’t know, but I’m thinking that maybe when I jumped 6 weeks ago and charged it up, it was fine, but something has since drained it to the point that it won’t take a charge or a jump any more.

Your plan sounds like a bandaid and you may not even be putting it on the wound. For instance your car may be overcharging the battery, this will kill the battery. Trickle charging it will not help here and may hurt & 2 batteries will just prolong the batteries by exactly a factor of 2.

Some auto parts places will diagnose the charging system for free (or let you borrow the tool to do it yourself). That would be the cheap place to start. Or at least get a $10 plug into the cig lighter charging system indicator.

Yeah… dead battery. It was drained and jumped and it lives a sporadic lifestyle.

Replace. Batteries that live a life with low charge and are drained/jumped are on borrowed time.

You killed it dead.


If you’re right, will swapping out the battery at least allow me to start and run the car? That would be cheaper than a tow. Even if I kill another battery.

Yes it would, also a jump start kit could also be a option but one had to keep it charged.

I am also wondering if you have a defective ground since you tried to jump start it that way and it failed. That could be the problem.

Perhaps. How old is the battery?

I would concur. Obviously, there’s something draining on the battery while the car is parked, so try to suss that out asap.

How old is the battery?

eta: Too slow.

Thanks for all the help and input so far!

I’m not quite sure what you’re saying here – could you put it differently?

How would this be determined, and could this also be the drain?

Several years. Not sure exactly how many. We’ve had the car since 2012, and I can’t recall ever swapping out the battery.

Is there a way to do this without a lot of special gear? I’ve already checked all the most obvious culprits (lights and cigarette lighters).

I’m very hesitant to take it to the shop because I recently took it to the dealer shop for a warning light, and it turned out to be something emissions related that would cost over 3 grand (probably more than the value of the car) to fix, but which wouldn’t affect anything until my next emissions test. With this in mind, I figured I’d drive the car until the next emissions test, and assuming it failed, trade it in and get a more recent used car (probably a more reliable/cheaper-to-fix model). So now if there’s anything significant wrong, I’m thinking that I just want to get the car able to start and run, and trade it in for something before it’s utterly undrivable.

In situations like yours, my first step is always to check/clean my connections. I’ve had cars that wouldn’t turn over start fine after cleaning up the terminals/connections.

Just a thought.

Thanks, I’ll try that. Probably won’t be able to until Saturday morning.

I’d just replace it, at a minimum 7 years old it’s at the end of its life. Old batteries behave strangely.

you can start here:

It’s basically a battery with build in jumper cables.

It would effect charging and cause your charging system not to operate correctly and could cause your battery to not charge properly while the car is running. So no it’s not a drain so much as a failure to charge.
With your emissions problem, perhaps I would just get a new battery and have the charging system checked (for free as I mentioned) and ride it out. Also consider that jump charging kit which is also useful in your next car as opposed to a second battery which may not fit your next car, and may not be needed at all.

Kayaker’s advice is great. Let us know what you find there.

Hmmmm, troubleshooting voltage drains are difficult. I’m unfamiliar w/ those cool, little Audis, so hopefully someone with more experience can help us with that.

Buuuuut, my guess is that the computer/life-support is always pulling a trickle from the battery. You don’t drive it often enough to replace that loss, so it becomes (more-or-less) cumulative. An old battery really dislikes a full discharge. Heck, brand-new batteries don’t appreciate a full discharge, but they’re young and full of piss and vinegar, so they can bounce back a little easier than a tired, old one.

In summary, it may be as simple as your connections. And that the battery is on its last leg.

When you’re at the auto-parts store, you could get a hydrometer. That’ll give you an inside-look at your battery’s health. Might put your mind at ease, too.

If you make wine, you might already own a tool to measure specific gravity.

I would second the new battery suggestions. After 7 years, it’s probably time. They tend to last around 5-6 years for me.

A coworker suggested this morning that I should try and jumpstart it again, but this time leave the connection (with the good car running) for 5 or 10 minutes before trying to start it, to actually charge up the battery a bit with the other car’s juice. If I can find someone to help me do that, I might try it.

When a battery gets toward the end of its life, this is exactly how it behaves. It often happens on a cold morning when the load on the started is greater than normal and jumping it is only a tempory solution.

Buy a new battery, and possibly a smart charger like this