12 Volt Charging Question

Sun Jun 06, 2004 7:34 am

Any idea what the voltage across the battery terminals should be on a 12 V system when charging. Trying to diagnose battery versus generator ?

:?: :?:

Sun Jun 06, 2004 1:04 pm

If a generator is charging as designed it should put out 13.5 V plus or minus a 1/2 V. A full charged battery will show 12 V plus . First check your voltage from terminal to terminal with a Digital volt meter . Then crank engine and bring engine speed up 3/4 throttle. Then check again, it should be putting out around 13 to 13.5.V's Say from terminal to terminal not running you you have 11.5V you crank and have 12.5V you are charging and at 12.5 it will keep the battery charged but when you turn the lights on or crank it 4 or 5 times in a row you have a dead battery. Also there is the (how many amps are you putting out ) Charge the battery then carry it to the auto parts store most can check it for a bad cell or battery. if it is not charged it will check bad or need charged so charge it first. Starters can also be bad when they get hot they can drag and not turn over. Pup

Fri Jun 18, 2004 8:28 am

I'm pretty sure the battery is not the problem, it takes a charge fine via a battery charger but is dead before I get the grass cut. Can I take a reading at the genaerator for the 13.5V and if the is good I guess I go to the voltage regulator.

Do you think this could also cause rough running under load as the battery die out ?

Fri Jun 18, 2004 4:32 pm

I think it was George Willer that had a very good article in Red Power Magazine on the charging system. Maybe it will make its way to the manual server with the other good information.

Fri Jun 18, 2004 10:02 pm


I think that was Jim Becker's article. And sorry they will not be made available on the manual server. :cry: Once submitted I guess they become the property of RP and not getting into that one...... :?

Course, if Jim or someone was to write an article like that FOR the server, :idea: that WOULD be a different story :D and be up faster than you could say POST IT :lol:

Sat Jun 19, 2004 7:38 am

Do you think this could also cause rough running under load as the battery die out ?

Yes as voltage drops the spark gets weaker.
Blue spark w/full batt.
Yellow to orange w/ weak or almost dead batt.

Sat Jun 19, 2004 2:18 pm

Thanks Dale

Any idea how to tell whether it's a generator or regulator probblem ?


Sun Jun 20, 2004 8:13 am


How long do you mow before the batt dies?
As for where to start I would do as pup posted then start checking all terminals for good connection.
Then start with the points in the regulator then go to the brushes in the gen.