Audi A4 battery going flat all of a sudden

Auntie · 20-03-2023 6:38pm #1

I've had flat batteries before - left lights on or some such. Jump start, run a few miles and it's fine.

Flat battery this morn, jumped, drove 30 miles to work. Battery flat again this evening going home.

It's charging and holding - I cut the engine out a few miles into the journey and started it again on the battery.

When I came home, I locked it up, but then removed the earth strap (I need to go out later and wondered was something draining it unseen). I notice there's a fair bit of sparking if I touch the lead to the battery terminal. As if there's still a decent draw from the locked up car.

At the weekend I changed a blown taillight bulb is all but can't imagine that affecting anything.

I suppose the battery could be knackered - I'll leave the earth strap off overnight and see. But anyone any insight into how to trace an invisible draw when the cars locked up?

Cheers

dontmindme · 20-03-2023 7:19pm

https://www.youtube.com/watch?v=KF1gijj03_0&ab_channel=EricTheCarGuy

Watch this

Dirty Nails · 21-03-2023 12:01am

https://www.boards.ie/discussion/2058289030/audi-a4-battery-going-flat-all-of-a-sudden

The spark is pretty normal & the video only applies to very old cars, Connecting & disconnecting the lead is waking up all the brains in the car, he should have waited for 5 mins before he decided he had a draw. Also cars with bonnet switches, you'd need to snap the locks shut to bypass them.

My advice get your battery tested first before looking for problems that mightn't exist

mikewest · 21-03-2023 12:10am

How old is the battery? Are you getting any warning lights? Have you had any random warning lights the lady while?

If it is starting fine after leaving the negative disconnected then you may have a phantom drain but I would suspect the battery first off.

Auntie · 21-03-2023 11:25am

https://www.boards.ie/discussion/comment/120381766#Comment_120381766

Can't remember whether I replaced this one or not but surely a car ought not drain a battery

artanevilla · 21-03-2023 11:27am

Probably just needs a new battery. Generally they last from 3-5 years.

artanevilla · 21-03-2023 11:28am

By earth strap do you mean the negative terminal?

Auntie · 21-03-2023 11:32am

https://www.boards.ie/discussion/comment/120382658#Comment_120382658

That's the one. Disconnected overnight last night and the battery was fine this morning (say 12 hours later) Whereas it discharged over an 8 hour working day when left connected yesterday.

BENDYBINN · 21-03-2023 11:35am

Would you ever have left the wireless on?

Auntie · 21-03-2023 11:37am

https://www.boards.ie/discussion/comment/120382675#Comment_120382675

It's an 07 car. No wireless that I'm aware of:)

Auntie · 21-03-2023 11:39am

I've noticed a warning light sometimes hang after starting since this flat battery thing started. Looks like skid control. Ought I pull the fuse for that and see?

Got a low brake pad warning about a month ago and ue to replace those with upcoming service

artanevilla · 21-03-2023 11:40am

Have anything plugged into the cigarette lighter? Dashcam, phone charger etc?

cml387 · 21-03-2023 11:42am

If you can't remember changing the battery it's probably old.

A dodgy battery may have enough volts to start the car immediately after a journey but it will soon discharge enough to cause the car to fail to start overnight.

Auntie · 21-03-2023 11:42am

See above re warning light. Ta..

Arnout · 21-03-2023 1:09pm

Sometimes batteries just die overnight. Or over-fuelstop. It happened to me that one day I was still driving no problem, the next morning the battery was dead as a dodo. New battery and all was well (and still is almost five years later). I had already owned the car for six years and the battery probably wasn't new when I bought the car, so it didn't do too bad anyway.

Over-fuelstop: my father left work one day, no problem. Stopped for fuel on the way home and the car wouldn't start anymore. Again: new battery and all was well.

Auntie · 21-03-2023 1:28pm

https://www.boards.ie/discussion/comment/120382693#Comment_120382693

Nope, nothing at all.

Auntie · 21-03-2023 1:31pm

https://www.boards.ie/discussion/comment/120383023#Comment_120383023

Except the battery is holding charge fine so long as I disconnect the negative lead each time I get out of the car.

Flat one morning - jump start

Charged on the way to work (30 miles). That would normally sort an accidently discharged battery

Went to go home that evening and the battery was flat again - jump start

Drove home and disconnected the negative lead for the evening/night

Reconnected battery lead next morning and the car started fine - battery plenty of life in it

Conclusion (logical enough): it's not the battery, it's something discharging the battery even with the car locked up.

Arnout · 21-03-2023 2:10pm

Good point there then...

Maybe interior light is on, or something like that? My kids keep playing with the switches...

Auntie · 21-03-2023 2:42pm

https://www.boards.ie/discussion/comment/120383392#Comment_120383392

Nothing obvious like that. I replaced a burnt out taillight bulb at the weekend but it's hardly that??? If it was consuming power, it'd light up :)

greasepalm · 21-03-2023 2:53pm

I had an old Gunson Testune Multimeter which i bought because it had a feature to show battery drain to help find the unit that was killing the battery like a stuck relay.

One would be removing the fuses and checking the needle to see it drop and then identify what circuit was causing it . Even car radios caused it.

cml387 · 21-03-2023 2:53pm

If you are determined it's a battery drain you need to connect an multimeter set to amps between ground strap and vehicle chassis.

It shouldn't measure more than 0.1 amps at the very most with ignition off.

Auntie · 21-03-2023 9:59pm

That's the ticket - put a meter on it and pull fuses. why didn't I think of that!!

I'll borrow a meter at the weekend and get cracking. Else route a big switch to the car interior where I can switch in and out the negative lead.

Contact!!

thanks for the advice folks - saved me a trip to the garawwwge, perhaps.

greasepalm · 21-03-2023 10:33pm

Dont forget plenty of hints and videos on YouTube

Auntie · 29-03-2023 5:06pm

https://www.boards.ie/discussion/comment/120383736#Comment_120383736

So:

Got a multimeter and hooked it up. 4amps being pulled with the ignition off.

Pulled fuses and found that the interior/glove/boot lighting accounted for 3A. A few bits and bobs from other fuses (e.g. dash clock) but couldn't make much impact on the remaining 1A. Although happy to have found 3A, I figured 1A would still drain the battery quick. "Hardly have two different problems occurring at the same time?" I thought.

Turns out that this multimeter thing is a bit of a red herring - the problem was simple and was as follows:

At some point during the fiddling around with the multimeter, I locked the car as I sometimes do: driver (or other) door open, press the central locking, then close the opened door - assuming it will now be locked because the cars been locked up.

Turns out that's false. The door which is open when the central locking operates stays unlocked when you close it. On my car anyway

And with it any manual light that happens to be on. If you have the glove compartment open or the reading light on and then central lock the car with a door open and then close that door > then the door remains unlocked and those lights stay on.

Press the central lock again and the remaining door locks and the glove/reading lights go out.

Problem solved: I was locking the car up the wrong way. The 4A drain with ignition key out was neither here nor there.

Thanks for all the assist - the multimeter helped, if only that it set me at the problem and I stumbled across the actual solution.

Arnout · 29-03-2023 7:36pm

Well done for finding the problem! Didn't think of that. Also because those lights on many cars switch off after a while anyway.

cml387 · 30-03-2023 7:41am

Top job. A future in auto electrics awaits you!

Auntie · 31-03-2023 9:07am

https://www.boards.ie/discussion/comment/120418346#Comment_120418346

I'm an engineer in industry and if I've found one thing that's true it's that 95% of problems are simple. The hard bit is finding that out.

dontmindme · 31-03-2023 11:18am

https://www.boards.ie/discussion/comment/120385658#Comment_120385658

That's the ticket - put a meter on it and pull fuses. why didn't I think of that!!

You thanked the post but never looked at the video in post #2??

Audi A4 battery going flat all of a sudden

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