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Posted by D Sherman [72.47.153.24] on Sunday, May 20, 2012 at 19:31:39 :
In Reply to: Re: voltage reg./gen. problems 6-volt posted by JET [75.53.129.55] on Sunday, May 20, 2012 at 19:07:31 :
It "might" be working okay. 36 amps at 6 volts is only 200+ watts. Lots of modern rigs have 100 amp alternators at 12 volts, which is 1200 watts. So, 36 amps really isn't a lot of amps. Also, it's not supposed to drop off with increasing RPM. What it's supposed to do is level off once the voltage gets high enough. A DC generator usually takes more RPM to make meaningful juice than an AC alternator, though the old alternators weren't very good either. Above 1000 rpm or so, I probably should level off. Don't expect it to drop down at 2000 or 3000 RPM, though.
The behavior when you idle is normal. One of the problems with the old generator type electrical system is if you leave the truck idling for a long time, especially with the lights on, you can run the battery down, even though you'd think you wouldn't. Sometimes this a problem when using a winch for some big project, for example.
The only thing that makes me think you may have something wrong is that the battery appears to be fully charged, and yet the generator's still putting 36 amps into it (assuming you don't have some other 36 amp load on, such as the headlights or a big heater blower). One sneaky problem that happens now and then is a shorted cell in the battery, which in your case would turn a 6.3 volt battery into a 4.2 volt one, so the regulator would always be trying to overcharge it.
6.4 volts at idle, however, tells me the battery isn't shorted and it's fully charged. 7.6 when revved up is a bit on the high side. As a general rule, it's best not to go much above 2.4 volts per cell, which is 7.2.
Could be be that your voltage coil is mis-adjusted? Maybe somebody once had an 8 volt battery in it and cranked it up for that? If it's the kind with the bendable tab, loosen the tension on the spring by bending the bottom tab up VERY slightly. If the voltage is then too low, you can tap it back down a little at a time with a screwdriver and a hammer. You won't be able to get the voltage set to any better than +/-.1 volts, because the vibrating points mechanism just won't hold a precision adjustment.
If you don't find anything obviously wrong, I'd be inclined to just run it like that for a while, being sure to check the electrolyte level in the battery frequently to see if it's overcharging badly.
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