View Full Version : Generator Output Test

24th March 2005, 18:51
As i have said before, i am no good at this amps, volts, watts, current, power, whatever thing. Anyway i wanted to test my generator. No problems; just wanted to do the test. Following Clymer, at the beginning of the electrical chapter.

My meter has a scale labelled mAMPS with three scales: 2m, 20m, 200m. The result i got was .015 on the 2m scale. The book says i need 10 amps or more.

Does .015 on 2m mean 15 amps? Obviously i am hoping for this.

Sometimes m means 1000; sometimes it means 1/1000. Those crazy b@$t@rds who set these things up otta be !@#$%%^.

24th March 2005, 19:15
mA is milliamps (hundreths of an Amp). So on a 2 mA scale, .015 is 1.5 milliamps. Does the test have you put the generator on a load? You won't draw any current from it unless it's loaded. Each scale setting on your meter is the maximum current expected before it goes off scale. Most meters will have a seperate input for measuring greater than the maximum current on the normal input. If yours doesn't, you may not be able to measure 10 Amps.

I'm not sure how the manual has you set up the test but it seems to me you need to load the generator, put a meter (with suitable current capability) in series with the circuit to measure current, and another meter across your load measuring voltage. Gradually increase the load until the voltage starts to drop off. That is your maximum current.

note: Never put your meter across the generator output on the Amps settings. The generator will see a dead short and you'll either damage the generator or at least blow the fuse in the meter.

24th March 2005, 20:38
mA is milliamps (hundreths of an Amp). So on a 2 mA scale, .015 is 1.5 milliamps ...

mA must be thousandths of an amp tho, not hundredths, eh?

In my math, .015 milliamps would be .000015 amps. 15 amps would be 15000 milliamps. Because i see 1 milliamp as being 1/1000 of an amp, not 1000 amps.

The rest makes no sense to me. "load the generator", "current", "volts": please do not confuse me or waste your good life time trying to commumicate this stuff to me. It did not get thru in Grade 11 Physics class in 1960, and it won't now either. Somehow, i managed 2, 1/2 universtiy science degrees without getting this part of stuff. In spite of this handicap, physics was actually my highest mark in 1st year at U!

It' all crazy.

24th March 2005, 21:37
Ugh, I misspoke. sorry.
The prefix "milli" means thousandths and in technical script is signified with "m". Millionths is "micro" and is signified with "".
1 Amp = 1000 mA = 1,000,000 A.

On your meter (I'm assuming it's a digital)...
@2mA scale, the highest it will display is .002
@20mA scale, the highest it will display is .020
@200 mA scale, the highest it will display is .200

The whole purpose of resolution scaling the display on meters is simply for accuracy. You may notice that the only thing that changes on the display when you switch through the scales is the decimal point. That just allows finer (more accurate) measurements at lower values.
In any case, those scales are not "heavy" enough to read 10 Amps.

If you can, scan and post the page with the testing procedure on it and perhaps I can see what they are doing.

EDIT: Nevermind on the scanning thing. I found the procedure in an old Haynes ironhead manual. It look as though they are just measuring the current from the output of the generator to the positive terminal of the battery with the regulator removed from the circuit. It should be a simple procedure as long as you have (get) a meter that will measure 10 Amps.

25th March 2005, 02:16
dwardy, please explain this. I don't have the grey wire in the photo going from the gen to the reg. I see the post on the reg marked as G, but alas there is no wire on it. What could this mean? Is it just an alternative ground? It would seem to me that the gen would ground to the chasis thru the engine. Or is this there for 3 brush models? Mine is the later hitachi 2 brush. Thanks!!!

25th March 2005, 03:29
This is the wiring shown for the '76.
Are you saying you only have 2 wires connected to your regulator?

1st April 2005, 01:50
nope mine looks just like that only the regulator also has a ground. I am using a later hitachi model generator.

3rd April 2005, 12:34
Unless you are running a pile of lights you shouldn't be concerned with amps.Amps is nothing more than the power being used by the components of the system.Your generator supplies power in volts 12-14,your regulator makes sure that the power from the generator stays within a small window around 12 volts so that things don't burn out.What power the light uses to stay bright is measured in amps.

How your generator is wired or how many poles you have really makes no difference,it still makes 12 volts.What it does do is give the generator more capacity for higher loads,more bells and whistles.


3rd April 2005, 14:16
I have a "battery minder" that a friend makes up for about $15.00. It has three leds (red, green and yellow) that tell me what's going on. Eliminates a lotta guess work.

3rd April 2005, 14:54
You know what? I have one of those.....its sold at Advance for about 10 bucks....same 3 leds, just have to wire it on.....They sell it as a charging system/battery tester.....helped me understand that my bike only barely keeps charging at idle..extra lights hurt at that time (take notice, those of you who are mounting passing/fog lamps hard (no switch). I find that if I idle too long with my fog lites on, the battery gets behind (so, of course, I HAVE to go for a ride then...)