Battery drain overnight?

Disconnect one of the battery terminals and put the multimeter between the terminal and the end of the lead. If it shows a current with everything switched off (which it almost certainly will), then you have a drain. Question is, how much? I would expect about 35 milliamps or so, because even with everything switched off current is still needed to maintain some functions.

Rob Graham

But don't do this before you've made sure that you've got your radio unlock codes. ;-)

It's quite likely that it's just that your battery is nearing the end of its life and needs replacing.

Tim

You have to use guile when carrying this out with some cars as the inrush current when connecting the battery can blow the DVM fuse. So best way is to make the connection with the DVM shorted, then remove that short after a short time.

Check the boot light and bonnet lamp (if you have them), switch breaks and the lights stay on and off course are un-noticed

Battery is only 6 months old.

then assuming that the vehicle gets reasonable use and is charging then it should stay charged. first thing I would do is check the charging, then charge and test the battery (even though it is recent don't discount it), then look for drain currents. you could also try disconnecting the battery overnight.

Only if its a bag of shit you bought from the Pound Shop.

Actually, you can trace the current drain quite easily and quite specifically - without disconnecting the battery.

1. switch everything off
2. open fuse block lid
3. take out one fuse and connect ammeter leads across the socket - make a note of the current if significant
4. replace fuse
5. rinse and repeat

that would not trace one of the most common drains: the alternator

there is often a very healthy crackle when connecting the battery, some vehicles fire the central locking, so the initial current can be far higher than is safe even for expensive multi-meters, and in any case why risk it? just connect the meter to the battery terminal, hold the battery lead against the terminal and connect the other meter lead to the battery lead, separate the battery lead from the battery keeping one meter lead on the battery terminal and the other on the battery lead, simples. read battery drain with little risk to anything.

Rubbish!

Some cars can take quite a bit of initial in rush current when the battery is first connected, more than enough to wreck a meter set on a

If there is any substantial discharge, as in a fault, then the meter is still at risk. Rather than using a meter for the first test, safer would be to insert a low wattage lamp in series with the battery lead to see if it passes enough to light it up - say a 16w indicator lamp, or a 5w tail lamp.

The best way is to short the meter terminals out until it has settled and make sure no doors are opened or lights are turned on with the meter in line. 35mA - ish is about right, though some cars may initially show more and the current required decreases over the first

It might also be worth checking the voltage across the battery with engine running, with various loads on and not running, to make sure it is getting a good charge.

I'm fairly certain that's not very common, it's just very troublesome.

The pound shop don't sell spare fuses for Fluke 867s so either your accounts been hijacked by the Tiscali idiot or you've lost it.

It would certainly trace the light in the boot and all that sort of problem.

In fact, I first did this over 40 years ago, when I had just learnt about electricity at school. By the time I located the problem (light in the boot ofc), my dad had already been sold a new battery and dynamo by the garage. If I hadn't found it, I think they'd have sold him a new car.

Shows how much you know about such things.

Oh - I suggest you look up how much a fuse costs for a Fluke DVM...

I've had the fuse go on the 10 amp range...

Isolate the different circuits in turn in the following order until the excess current stops.

Pull out each fuse in turn.

Pull out each relay in turn.

Remove the plug in the back of the alternator. (Usually involves accessing from underside of car)

GB used his keyboard to write :

The easy test is to open the boot, feel the light and if it is warm - it is staying on. Though some cars are fitted with a battery saver relay, these turn of the supplies to such things around 30 minutes after the car has been left undisturbed for that length of time. In other words leave it parked in the garage with a door open, the interior light should go out after 30 minutes and not come back on unless you close then reopen the door.

It's far more likely to be a shagged battery than a leak. The volts across them drop due to the overnight cold especially at this time of year.