DO NOT disconnect the positive whilst the engine is running, The battery releases Hydrogen Gas, which is highly explosive, disconnecting the battery with this present will ignite and boom, uve got a battery exploding in ur face.
Best way to check is with a multimeter.

a fully charged battery will hold 12.6v.
A fully functional charging system on an older vehicle is around 13.8 or higher

continuing from bailz..

and when you rev the engine, the voltage should not rise.
If the regulator is broken, the voltage will go well above the expected (normal) 13.8v -> 14.4v

check battery voltage when off... start car then re-heck voltage,,, voltage will be higher when running

Warning:
1. do not try this with newer cars. Those with electronic ignition or integrated-regulator alternator can sometimes be damaged. Like some late 70s Datsuns

2. do not leave the cable off for more than a second. The alternator output can go super high as it tries to regulate the voltage.


A more reliable test, easier too because you don't need to unbolt anything, is to use a voltmeter. At 1100 RPM, the battery terminals should read 13.5-15.0 volts. Too high is a problem you won't catch with the cable-off test, but you will with the voltmeter.

Positive sumith, thats where the batt gets it charge from, through that fusible link wire thats attached to the pos battery cable.

Hi Whitesedan

Thanks, no matter if it is positive end or negative end of the battery ?

Thanks
Regards
sumith

Disconnect battery while engine is running, engine should continue to run on charge from alt.

Hi Guys

how do you check whether the alternator is charging you battery or not in a simple and easy way ?

thanks
Regards
sumith