Ok so here's a little run through of my sorta say problem. 110cc mini hummer has had a few electrical problems but this one is just weird.

First the relay for the starter motor craps out on me...TWICE so I get fed up and replace it with a larger relay and then no problems there it starts fine.

I then got fed up with the battery being so junk so I got an 18ah 12v battery and wired it up and zip tied it to the back rack (yes it IS super ghetto) and haven't had a problem with the battery dieing. I had it like this for about a month and haven't had to charge the battery once.

The problem is one day I was bored so I thought I'd meter the battery to see if it was charging like it should or if I'll have to put a charger on it myself. Well I got some weird finding.

Off: 12.3v
idle:12.35V
about 1/2 throttle 9-10v

So my question is what the hell would be causing this?

 

A bigger battery does nothing except make your quad heavier (and top heavy at that), and increase the time you can crank your starter before it goes dead. A good small battery can crank the quad for two minutes or so. But my reasoning is that if it doesn't start in two minutes, then why would it start in the next five minutes? A bigger battery offers no advantage at all on a stock quad in my opinion.

If you're running a winch, or something else that draws a *lot* of current, that would be a different story.

This is a very strange problem. Where are you measuring this voltage? Right on the battery terminals?

Lets assume for the moment that your battery is fully charged, and good. For you to drag an 18 amp hour battery down to 9 volts would take a load of 150 amps. That's roughly 1350 watts. 1.5 horsepower! I would think smoke and fire would accompany these conditions. Do you have a main fuse? It is only 7 amps or so. This does not compute.

Thus I suspect you aren't measuring right on the battery terminals, and there are other things going on like bad connections somewhere. Or your battery isn't charged, or it is ruined from being drained slowly without beng recharged promptly. Or simple measurement error. It happens to me too. Measure this again and see if the results are the same. If you get the same results then disconnect the regulator and see if it that changes anything.

If your big battery is toast then it is possible to suck it down with a lot less current than 150 amps. This would make a lot of sense if your charging circuitry is not working and you've been slowly sucking the battery dry and leaving it sit discharged. Leaving batteries sit in a discharged or semi-discharged state ruins them very quickly.

Maybe your first battery became junk because it wasn't kept charged up?

 

Yah I was going right off the battery terminals. I'll test it again in a bit.

Thanks