Testing a Battery/Alternator with a Voltmeter...

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gerpena · #1 Unread post by **gerpena** » Fri Sep 23, 2005 4:09 am

I am trying to figure out if i have a battery that needs to be replaced. 2 weeks ago i had it recharged and it worked great until yesterday when my bike wouldnt start.

how can i figure out if the battery needs to be replaced or if there is something else draining it? perhaps the alternator is bad?

BudmanTom · #2 Unread post by **BudmanTom** » Fri Sep 23, 2005 4:34 am

Correct me if I'm wrong, but I thought that if the bike was running and you pulled the positive cable off the battery and the bike died it was the alternator?

gerpena · #3 Unread post by **gerpena** » Fri Sep 23, 2005 5:25 am

BudmanTom wrote:Correct me if I'm wrong, but I thought that if the bike was running and you pulled the positive cable off the battery and the bike died it was the alternator?

Thats a great suggestion.

Is this a reliable way to determine if the alternator is good guys?

Iain · #4 Unread post by **Iain** » Fri Sep 23, 2005 7:29 am

Couldn't you check the battery with a voltmeter? If you don't have one I'm sure you can pick a multimeter up from radioshack pretty cheap.

If you have both an ammeter and voltmeter, or a multimeter that will do both at the same time, couldn't you connect the negative lead of the ammeter to the positive lead on the battery, then connect the positive lead of the ammeter to the cable that normaly connects to positive lead of the battery. Then you would be able to read the current flowing from the alternator as the bike runs. Then just connect the positive side of the voltmeter to the positive lead on the battery, and ground the other lead on the engine or frame, whatever you want. Thats assuming your bike is ground over the negative terminal. Then when the bike is running, check to see how much of a current the alternator is supplying the battery, and how much voltage.

Someone correct me if I'm wrong, but this is what I would do for my bike.

-Holiday · #5 Unread post by **-Holiday** » Fri Sep 23, 2005 7:38 am

I've suggested testing the battery with a meter in every one of your threads about your battery problems...
The answer is still the same. Get a meter and test your battery, and your alternator.

gerpena · #6 Unread post by **gerpena** » Fri Sep 23, 2005 8:59 am

-Holiday wrote:I've suggested testing the battery with a meter in every one of your threads about your battery problems...
The answer is still the same. Get a meter and test your battery, and your alternator.

Holiday,

I am actually getting a meter today, thanks for your suggestions. I actually printed out your previous advice and plan to look into it. I will check it out tonight. I didnt meant any disrespect.

gerpena · #7 Unread post by **gerpena** » Fri Sep 23, 2005 9:06 am

Iain wrote:connect the negative lead of the ammeter to the positive lead on the battery, then connect the positive lead of the ammeter to the cable that normaly connects to positive lead of the battery. Then you would be able to read the current flowing from the alternator as the bike runs. Then just connect the positive side of the voltmeter to the positive lead on the battery, and ground the other lead on the engine or frame, whatever you want. Thats assuming your bike is ground over the negative terminal. Then when the bike is running, check to see how much of a current the alternator is supplying the battery, and how much voltage.

Thanks Iain.... I am going to try this tonight.

-Holiday · #8 Unread post by **-Holiday** » Fri Sep 23, 2005 9:23 am

Not a problem, just wanted to make sure you're hearin what i'm sayin

this stuff isnt that hard to troubleshoot, you just need to test a few basic things.

Heck, if you're close to the Philadelphia PA area i'd be happy to drop by and give you a hand ...

Good luck!

gerpena · #9 Unread post by **gerpena** » Fri Sep 23, 2005 9:37 am

-Holiday wrote:Not a problem, just wanted to make sure you're hearin what i'm sayin
this stuff isnt that hard to troubleshoot, you just need to test a few basic things.

Heck, if you're close to the Philadelphia PA area i'd be happy to drop by and give you a hand ...

Good luck!

hahaha..... id take you up on your offer but i dont think you'de be able to ride to seattle and be back in time for work on monday. thatnks for the generous offer though.

i am excited to do some testin' tonight though!

Nibblet99 · Fri Sep 23, 2005 9:38 am

easiest way to check your alternator is to have the engine idling with the headlight on... then put a couple of revs on.

If your headlights get slightly brighter, then your alternator works.

also if you put a voltmeter across the battery terminals whilst the bike is running, the volts registered should be ABOVE 12V (Possibly 6V if you've got a wierd bike)

I'm not sure all bikes will run without a battery, depends on how many coils in the alternator, and their positioning

***EDIT***

Oh yeah, and putting the ammeters in line with the battery, and starting it is A BAD IDEA... Most ammeters won't take the amount of amps pushed through whilst running the starter motor
I don't know how many it'll try to draw, but cars typically take between 40 and 80 amps, so I'd guess around 20-40 amps for a bike

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Testing a Battery/Alternator with a Voltmeter...

Testing a Battery/Alternator with a Voltmeter...

is that right?