checking battery leakage current

you need an ammeter.

Disconnect the battery, and connect the meter between the battery terminal and the battery clamp.

Somewhere around 0.05 amps. Probably less.

The message from "SimonJ" contains these words:

Or a professional.

But DON'T ATTEMPT TO START THE ENGINE! - otherwise your ammeter will melt or explode...

Darren

The message from "Darren Jarvis" contains these words:

No it won't - it'll just blow its internal fuse. Usually 10A. Unless of course you've an unfused ammeter.

It may blow it's fuse anyway as the ECU may want a gob of current to relock the doors as you reconnect it. Pull the central locking relay first.

Save all this trouble and use a DC type clamp ammeter. Ideal for this test and also to measure residual charging current by starting the engine, running at fast idle and switching loads on one by one and check that a few amps continue to flow into the battery. Once you have had one of these meters you won't want anything else.

Bob

Going by the battery voltage alone, 12.27 is a 3/4 discharged battery after having stoof for that length off time. A fully charged battery should measure approx. 13volts after having stood for 12 hours, with 12volts being considered fully discharged.

To check battery discharge, connect an ammeter in line between the battery negative terminal, and the vehicle earth lead. The ammeter should show less than 0.01A, although there may be an initial surge of a few amps as the battery is reconnected which should only last for a few seconds. Other option is to connect a 12 volt 5watt bulb in the same way if you don't have an ammeter handy. The bulb might light up briefly when it's first connected in the same way the ammeter might show a surge, but should go out after a few seconds.

Yes. Mine does as you connect the battery. And Fluke fuses are expensive...

The message from "Dave Plowman (News)" contains these words:

I cooked a neighbour's Fluke once - and it wasn't just the fuse. Cost me nearly £80 to get it serviced.

Heh heh. They're only for the dedicated, but super if you're into that sort of thing. They even feel nice just to hold.;-)

But an under 5 quid Maplin DVM will be fine for most. Or check Ebay - a pal got a decent one with temperature probe brand new off there for 25 quid.

The message from "Dave Plowman (News)" contains these words:

I know - mine was 60 miles away so I borrowed his.

Go on, how? (Obviously I've never fried one by letting someon else near the on button for the 15KV lampignitor, cos it would be very silly to have ones fingers in there :-( )

Thanks for the replies. Wish I had read this before starting as I did blow the multimeter fuse, Doh! (Luckily had a spare from another meter) I had it set on the 200mA fused setting but as you say it surged well past that when first connected. I'll chalk it up to experience.

I think it may be leaking more current than it should. With key removed and everything off the meter is reading 0.07 (68mA). With one of the fuses removed the current dropped down to under 0.01 (6mA). The fuse removed operates the central locking, boot release and radio. With the fuse back in place and the radio disconnected the meter was reading 55mA (so the radio backup memory is consuming around 13mA which I think is about normal). Would you say that 55mA is excessive for the central locking and/or boot release? I don't see why those items should consume any leakage at all as I would have thought they would only use current when actually operated?

For time being I'm thinking of just leaving the fuse out as I can easily live without the central locking & boot release, and rewire the radio.

The message from DuncanWood contains these words:

D'yer know - I'm damned if I can remember. I do remember picking it up from their depot in Watford and causing mayhem by paying cash for the repair.

The message from "Mark" contains these words:

Remote control locking? If so - it'll be the quiescent current of the receiver.

Just basic key operated C/L on the Nexia. I had a look through the owners handbook in case some were fitted with remote C/L but there's no mention. I'll have another look tomorrow and see if I can narrow it down further.

I still use a AVO model 10 for most stuff. OK it's not as quick as a £5 maplin job but I suspect it's still just as accurate.

The Weston Cell it came with though is now dead sadly....:-(

Ah, now is that the battery with strange terminals for resistance testing? I never heard it referred to as a weston cell, but then when I was in the REME, I wouldn't have, it would just be "battery".

I've just dug my AVO out, and looking on the back it says it's a Model 8 MkIII. I don't know when it dates from, it was ancient when I got it. It hasn't had it's battery for many years now. I took the battery to an electrical shop and they laughed at me :-((

Steve