CJ750 toolbox
An ammeter for a CJ by Ross Kowalski

"I was thinking on the subject of ammeters and forgot the best thing about them—they tell you when your battery is getting ready to die (maybe taking other components of the charging system with it.)

The classic reason to have an ammeter is to see that the needle does not go back to 0 (or very near 0) ever. This can mean several things but it always seems to mean get a new battery.

Usually after a few minutes of charging the battery will no longer accept electrons (it is full) but if the battery has a short across its internal plates from vibration it will never stop accepting electrons and the ammeter will always indicate a 5A or so charge.

You might think, "oh the battery is getting 5A all the time, great!" but what you should really be seeing is a 0 and saying "oh the battery has been recharged and everything is in balance with the electrical system, great."

If you think about what the ammeter is doing it all makes some sense. If you have any questions, feel free to e-mail me and I can try and answer them."


Ross (ross.kowalski@gmail.com)

"On either a 6V or a 12V bike, cut the wire that charges the battery and put the ammeter there. The ammeter has two terminals on the back, attach each to the ends of the wire you just cut.
I drew the ammeter in the proper location on the 6V bike diagram.
I just highlighted the wire on the 12V diagram because it was too dense.

DC ammeters are all the same voltage so a 12V works as well as a 6V. If it reads backwards flip the wires. That's it.

The only problem is finding one that has a narrow enough range to be useful. A 30-0-30 ammeter is designed for cars with big generators or alternators. A 10-0-10 is more what you are looking for.

They aren't common anymore but you could check out old tractors on eBay. They charged with about the same amperage as the Chang.

Once you have the ammeter installed here is how it should work. With the engine off and switch to the left (no lights) the needle should be in the middle (no charging or discharging.)

With the engine off and the switch to the right (lights on) the needle should be on the — side by about 5~7 amps (discharging 5 amps.)

Immediately after starting the engine the needle will likely be still read as discharging until you rev it a little and the charge light goes out. At that point it might might read as charging 1~3 amps at idle. (Not much charging takes place at idle.)

Running the engine at driving speeds (either really driving or just maintaining a high rpm in neutral) the needle should be on the + side by about 5~7 amps (charging the battery which was depleted in starting.)

After charging for awhile at 5~7 amps the needle should drop back to 0 or just to the + side of 0.

When I start my 6V bike which only uses the battery for the ignition and lights, the battery recharges in a minute or two because the only thing it really needs to do is replace the electricity that was going to the headlight just prior to the engine starting.

I am sure our 12V bike takes longer to recover after starting because the starter uses a lot of electricity."