How to test charging sytem?

[chiroken]

Hello,

Couldn't find the "dummies" version in the archives.

I've just bought a 2007 Tohatsu 9.8hp 4 stroke that has 5 hrs on it. The previous owner has never used the electric start or charging system and I would like to test them. Once on a battery the start button is a no-brainer but how can I test that the charging system is working correctly?

I do have a voltmeter but limited knowledge. Am I testing across the 2 battery terminals and what exactly am I testing for?

Thanks in advance,

Ken

 

[waterinthefuel]

Re: How to test charging sytem?

Ken, this is a very basic and simple test.

First, without the engine running, check your battery voltage by placing your voltmeter on volts DC either in the up to 20v range or in the auto detection range, depending on what voltmeter you have. Put the red voltmeter lead on the positive and the black on the negative. Read the meter. It should be somewhere between 12.6 and 12.8 volts.

Now, start the engine and slowly open the throttle to rev it to about half throttle or a little less. Place the voltmeter leads the same as you did with the engine off. You should see the voltage start climbing, it should climb above battery voltage by at least a volt. If it makes it to 13.5 volts I would say its working fine.

Hope this helps.

 

[Silvertip]

Re: How to test charging sytem?

Adding one other little tidbit to the above: Before starting the engine, and depending on the state of charge of the battery, it may not read 12 - 12.6 volts. That does not mean there is a problem. It only means the battery is not fully charged. Even after starting the engine, it may take awhile for the meter to begin climbing.. Again -- it all depends on if the battery is fully charged or not to begin with.

 

[chiroken]

Re: How to test charging sytem?

OK, thanks to you both for the info. I know better than to assume, but I'll assume my battery is well charged. I will watch to see what it initially reads though.

Thanks