Battery drain - how much is too much?

[DuraAce]

How much should it be?

Is about 140 mA excessive?

[Alpha Omega]

Measure the current draw after the car has been left standing for an hour
0.14 of an Amp is too high, 0.05 of an Amp Max is a borderline acceptable figure but there are different draws on different vehicles and you do need to find out the acceptable figure for your vehicle - Contact the dealer
A higher draw than the above will not flatten a big battery of a vehicle that is in everyday use but this doesn't in any way mean that it is acceptable

[DuraAce]

Hmm, thought it might be a bit high. that was taken after car had been stood for an hour. Battery doesn't go flat if car is used daily but when I leave it for 10+ days it is sometimes flat.
More investigation required..

[GreenV8S]

140 mA is enough to drain a 50AH battery in about a fortnight. There may be a few old cars that would have a current drain this high (my V8S is one of them) but any modern car should have a drain of less than half that.

Worth checking that the stereo is switching off with the ignition, the alarm isn't triggering (that can suck a lot of current), and no door/boot/bonnet switches are failing in the closed position.

[DuraAce]

Some good ideas there, ta.
I'll get the multimeter out tomorrow and see what I can find.

[Alpha Omega]

As GreenV8S has mentioned, incorrect stereo wiring is a favourite, many stereos are wired incorrectly, if your stereo is wired to a permanent supply rather than a switched supply from Aux ignition key position that is enough to put a drain on

[buzzer]

I find the battery isolator below great for checking battery drain... they are about £5 on Ebay. you can connect the ammeter across the clamp and turn the know which makes things easy. Lots of cars take time to fully switch down and I find it a fiddle to use the ammeter without the clamp.

recently had an issue with a jeep where I could not find an intermittent drain... after literally weeks of trying I had the ammeter connected across the isolator and it was showing a few low amps.. the door was open so I expected to see a few. then all of a sudden, the wind moved the door slightly, and the ammeter shot off the scale!

That gave me a clue... I looked at the wires from the body to the door and found one broken! hard to find as the copper in the wire was broken, but the insulation was OK. it was only when I tried to stretch the wire I could see the break.

[DuraAce]

Well, after messing about for several hours we have a possible solution....
Tried fuse removal and voltage drop tests across fuses. Couldn't get it to drop below 90mA.
Checked battery voltage and it was only 12.2v. Popped the charger on for a couple of hours. Tested again at 12.6v
Drain is now 20mA!
Borrowed a friend's battery tester, only manages 340cca against stated 640cca on the battery. Tester says battery health is only 50% and should be replaced. Perhaps the failing battery was causing issue in the ecu's, making something not shut down correctly.
I'll test the drain again in the morning after it's sat for 12 hours.

Edited by DuraAce on Thursday 8th June 18:08