Voltage at Terminals

[henry F]

Following the numerous flat battery threads
(and not wishing to add another)

how with a voltmeter can I best detect failing battery on my surf.
placing meter across batteries pre-start would show 12V right,

so with someone cranking engine
another quick meter check, would that show dud battery.



or have I got wrong end of stick?

[Apache]

Not as easy to do as it sounds really. With the Surf, you'd need to disconnect one at a time and see if they hold up under load, otherwise you've no way of knowing which battery is low.

However, to do this properly, you need a known load rather than cranking, though cranking will give an indication if one holds the voltage up MUCH better than the other, in fact you'll probably find the duff one wont spin the engine over properly.

(Apologies if I'm teaching gran how to suck eggs here) Batteries are specced with a cranking current capability, and an Ampere Hour rating. In other words, they will provide a certain current for a certain length of time before keeling over.

[NiftyNev]

Proper load testing is needed but you can do a basic check one battery at a time. Do the first test as normal by placing multi meter on the battery posts. Crank the engine and make sure battery does not drop below around 10V. If this is ok then do a basic load test. If voltage drops to below 10V then do not do the next test. The battery will be in poor condition. Before starting turn on headlights with high beam, turn on blower fan at high setting and allow to run for a couple of minutes. Crank engine with these still on while checking voltage at the battery posts. A voltage drop below around 10V would suggest suspect battery.

Nev

[henry F]

Guess to be sure its off to another battery supplier probably then

just thought there might be a good indicator that was all