does anyone else suffer from their battery dischaging? i can loose about 0.4v overnight which isn't good.

it's not the battery or alternator as these have been changed/uprated. i am yet to have a complete flat battery but leaving the car stood over the weekend always hammers voltage!

is this a common fault with octys and may it have anything to do with the k-wire on my aftermarket headunit?

Hi Marko

You say you are loosing .4 of a volt over night, but when are you measuring it ?

If you measure the voltage just as you pull up then you will get a say fully charged battery, but if you leave it for a couple of hours then the voltage will drop.

The other thing, when did you notice the volt drop? just the last few days/weeks ?

as the colder the weather the lower the voltage of the battery, so if its just started being a problem, then it poss down to the colder temprature that we are having.

and I would not worry about .4 of a volt, if you said 4Volts then it might be a diffrent matter, just a test, with every thing turned off, what is the current draw?

Steve

it's been an on going issue since owning the car ( a year). i know where your coming from as regards just turning the engine off! my currant battery is a hawker 1700 deep cycle monster of a battery and this still looses a bit of charge over night! if i disconnect the battery over night it doesn't loose voltage

i'm thinking either there is a short somewhere or the aftermarket alarm (cobra) is to blame. i'm pretty handy with electrics but this one is stumping me.

just a test, with every thing turned off, what is the current draw?

how can i test this with my trusty multi metre?

Car off... alarm/deadlocks/remote locking sensors/digi readouts etc etc all still on using power

As mentioned about voltage drop will tell you very little about a current drain. You need to know how many amps are being drawn with the vehicle at rest. When measuring current drain with an ammeter you need to have it in the circuit (dont plonk it accross the battery, it will die). Disconnect the earth and put it in between the earth and the body. Best method is to use an amp clamp (as on VAS 5051) and this will monitor the drain without interupting anything by measuring the flow of electrons through the wire.

Do remember though it will take up to 20 mins for systems to power down and ECU's to go into sleep mode. After this you shouldnt see anymore than 0.2 amp drain. Remeber also to flick the bonnet catch across when testing so the alarm (if fitted) activates fully.

Rather than checking battery voltage which varies with temperature ,how long since car ran,how long journey was etc etc,you need to put an ammeter in series with the battery + ve terminal. I would not expect this value to be more than 20 to 50 milliamp (1 milliamp + 1/1ooo of an amp (0.001 AMP) . If the reading is higher you can then disconnect items to find out where the current is going.

There will always be a small draw of current ,due to car clock,radio even if off,alarm ,and other car running electronics. Remember you may lose radio tuning data when the battery is disconnected. The way to do it is to fit the ammeter across the positive battery ,and the outgoing wire(s) before mechanically disconnecting the terminal. The meter needs to be set on a high setting ,then switched down range to get correct reading. To give an example if 100 milliamp flows for 10 hours ,then 1 ampere hour has been taken from the battery,which has a capacity of 50 to 80 ampere hours total capacity when fully charged.

I would also consider the charging circuit ,and or battery may be at fault in your case.