How Do I Check The Alternator Is Charging Properly ?

[jkspoff]

I had a flat battery this morning and have read a lot of the forum about people checking that their alternator was working correctly using a meter, how do I do this before I splash out on an unnecessary new expensive calcium battery, which is now working ok after a trickle charge and drive out, but I've had a new alternator pulley fitted recently and wanted to make sure that its not the alternator that playing up again, the Unipart battery thats in has a sticker that says 'recharge 01/08', does this mean it from January 2008 or it was recharged then ? Edited December 28, 2009 by jkspoff

[Richard gal]

The recharge means it was on the shelf in late 2007.

 

If you have a voltmeter put it across the battery terminals, with engine off it will be about 11v, start it up and should be able to get to about 14.5v after a few mins, dipping to 13v with lots of things on.

 

Checking Amps is a little more difficult

[RADIOTWO]

I had a flat battery this morning and have read a lot of the forum about people checking that their alternator was working correctly using a meter, how do I do this before I splash out on an unnecessary new expensive calcium battery, which is now working ok after a trickle charge and drive out ?

 

Have you got a digital multi meter ?

 

If yes, check the battery voltage when the engine is not running, you will get about 12.0 to 12.5 Volts depending on how well the battery is charged up(or not)

Then start the engine, and the voltage should go up to about 14.5 Volts, then turn every thing on you can think of, ie, lights, heated rear window, blower motor,

and any thing else you can think of, again check the voltage, and should be about 13.8 Volts or more, and just to say, you need to run the engine @ about 2000 RPM.

 

there is another test, but you need a high amperage Amp meter that will read up to 200 Amps (or so)

 

You also say about the battery, you need to do a drop test on that(no I don't mean drop it from 4ft) its a load put on the battery for a certain time, but you need to

make sure the battery is fully charged

 

Radiotwo

[jkspoff]

This is great information, I will invest in a digital multi meter today and try all the above mentioned, as it'll come in handy anyway. Will see if it starts and keeps the charge today, as a calcium battery from 2007/8 should still be keeping power. I suspect with recent short journeys and lots of electrical equipment turned on it might have just lost its full charge for a while.

(If I do need a new battery Halfords are selling a Bosch silver calcium battery with 5 years guarantee for

[RADIOTWO]

This is great information, I will invest in a digital multi meter today and try all the above mentioned, as it'll come in handy anyway. Will see if it starts and keeps the charge today, as a calcium battery from 2007/8 should still be keeping power. I suspect with recent short journeys and lots of electrical equipment turned on it might have just lost its full charge for a while.

(If I do need a new battery Halfords are selling a Bosch silver calcium battery with 5 years guarantee for

[jkspoff]

All seems fine now, the battery kept its charge overnight after trickle charging it for a few hours, had a run out to the coast and it appears to be charging ok. I will put it down to the extreme cold weather we've had recently and will still buy a voltage meter at some point to double check all is ok. Thanks for all the advice.

[jkspoff]

I have just tested the alternator and battery.

The battery is showing over 12 volts when engine is switched off and nothing switched on, so I take it that the battery is ok.

With the engine running and everything switched on including the electric windows going up and down the reading with alternator running is around the 11-12 volt mark, is this right at tick over only revs, maybe 2000 revs would show better, will try again ?

When nothing electrical is switched on and the engine is running, the reading is over 14 volts, so the alternator is doing its job it seems, but sufficiently ?

Edited December 30, 2009 by jkspoff

[bj2004]

yes thats fine

[Mirez]

The battery is showing over 12 volts when engine is switched off and nothing switched on, so I take it that the battery is ok.

 

No, depends on the exact voltage, an ok battery is over 12.4V with no draw (a good battery is closer to 12.6V) anything below 12.4 and its on the way out.

 

When nothing electrical is switched on and the engine is running, the reading is over 14 volts, so the alternator is doing its job it seems, but sufficiently ?

 

Yes-ish, again depends on exact voltage but over 14V is ok, the closer to 14.4V the better but at idle you may not achieve that.

 

12V in electrical terms is nothing really, so getting good current at that voltage becomes tricky and hence why it'll drop off with big loads. Its the same reason truck's use 24V and why several years back the car industry wanted (still wants?) to change to 42V.

[jkspoff]

OK thanks for all the advice, I think its ok then, I realised that my ipod had been charging for 3 days that more than likely didn't do it any good !

On another note I was just wondering on the multi-meter dial which one it should be set to for the Galaxy testing ?

[bj2004]

hi

you can leave your i pod on charge that wont bother you much you want to have the meter on the 20v dc scale thats one position to left of what its on now the diode test position 25 past will be ok for testing continuity as would the ohm ranges make sure the cables are not powered tho when using those ranges

[RADIOTWO]

hi

you can leave your i pod on charge that wont bother you much you want to have the meter on the 20v dc scale thats one position to left of what its on now the diode test position 25 past will be ok for testing continuity as would the ohm ranges make sure the cables are not powered tho when using those ranges

 

Sorry BJ

 

Just look at the picture again !

 

You are right with the 20 volt DC, but the pointer is pointed at the temp setting, the meter is reading 24 degrees C

 

so turn the dial all the way round (180 degrees) and then one to the left

 

Radiotwo

[jkspoff]

So this one here circled on the pic ?

[Mirez]

So this one here circled on the pic ?

 

 

Yes!

[RADIOTWO]

So this one here circled on the pic ?

 

Yes that is correct ! but make sure the bar in the dial is pointing to the 20(as circled) with the mark pointing at the 20 Volt DC (at the moment its pointing at the temp setting)

 

Radiotwo

[Sweulf]

HI !

 

Black&Decker have a "smart" battery charger that can check that the alternator is working properly.

regards ulf