Battery keeps depleting over night

[colinwoods]

Hi all,

I've just had my car repaired following a small crash into the back of a Volvo. The garage dos a great job however my battery keep depleting every night. Something is draining it but I've checked that the interior light, radio and headlights are off and still it depletes.

Is there anything simple I should check? I'm guessing something under the hood is sucking the power out?

Any thoughts?

Thanks all

[tony g]

Have you checked the boot light?

Tony

[cliftyhanger]

You really need to get an ammeter and check circuits if you can't find it easily. I have a couple of these (similar at least)
http://www.ebay.co.uk/itm/DIGITAL-LCD-M ... SwMmBV3sPJ

and they will measure up to 10A, more than enough for your purposes.
Put it between the neg terminal of the battery and the battery lead, and you can then start disconnecting circuits. Soon see which circuit the issue is on, and then it gets easier (sometimes!)

[Mad Mart]

Yep, what he said ^^^. It's called parasitic drain.

[Jon Tilson]

Almost always the boot light.....

Jonners

[Mahesh]

Good to hear your car is back on the road, there aren't many I see in this part of London.

[colinwoods]

Thanks all. Excellent responses...

So, I've ordered an ammeter as I think these are good to have anyways. I don't have a light in the boot, so it can't be that.

I have had the battery drain all the way the past a couple of times by leaving a light on (classic) of which I understand can kill a battery. And, the car has not been driven for nearly two months whilst the rust was getting sorted. Would this have killed the battery?

[cliftyhanger]

That, along with the cold weather, will deplete a battery. But you said it was going flat overnight?
If the battery is a few years old that won't be helping either.
I would start by getting the battery fully charged, and take it from there. You can take it to a garage and get a drop test done to check the battery health.

[MIG Wielder]

Hi all,
I've just had my car repaired following a small crash into the back of a Volvo. The garage dos a great job however my battery keep depleting every night. Something is draining it but I've checked that the interior light, radio and headlights are off and still it depletes.
Is there anything simple I should check? I'm guessing something under the hood is sucking the power out?
Any thoughts?
Thanks all

If you have had recent body repairs done and it involved welding near the front, then another possibility is that one or more of the " Live side output diodes" in the alternator has gone faulty. There is a recommendation to always pull the plug on the alternator before welding.
How to diagnose this ? Fully charge the battery and then disconnect the large 3-way plug at the back of the alternator. It is held on by a wire clip. If the car starts O.K. the next morning then its a replacement alternator.
If this is not the cause, then remove the fuse running between the Brown and Purple wires overnight after charging the battery. If the car starts first thing the next day then there is a problem in one of the other "always live " circuits. ( Clock / courtesy lights / radio memory keep alive circuit etc; ) Then its down to checking with the multimeter. Anything more than 25mA would be suspicious.
HTH,
Tony.

[Jon Tilson]

Nice one Tony...

That;s my 2nd most common cause of battery discharge after the boot light...

Jonners

[colinwoods]

Thanks guys, this is awesome advice.

Just a footnote, should my Vonts gauge show the battery at 12v?

[GTS290N]

No, it should show around 14.5 volts iirc. Your alternator is not charging, obviously check the wiring first. A DVM is your best friend.

[tony g]

If volt meter shows 12v while running its not charging enough, but when ign on it may show 12 (if its anywhere near correct of course.
Tony (migweider not me) is possibly on the money again. If its been welded and the alternator has suffered a surge then battery will deplete even while driving. First basic check with mutimeter will be engine running and meter terminals across battery + and -. If no more than 12.5 with no accessories or lights on its not charging enough (duff alternator) Stop press: make sure the fan belt is not embarrassingly loose

Tony

[tony g]

GTS290N you beat me while I was waffling lol

Tony

[Toledo Man]

Don't trust the in-car voltmeter. It might not give an accurate reading. Take a reading across the battery with a digital multimeter to get an accurate voltage. You can also use a multimeter to measure a parasitic drain if it can also measure amps (most do). If the diodes have gone in the alternator then it might be worth repairing it. You can also fit new brushes at the same time and your alternator should be as good as a new one.

Let us know what you find out.