charging system redux

[zipster]

Any help appreciated. My '77 is still charging at 17 volts. Just replaced the voltage regulator last week. Can't the rectifier overcharge the system? I've tried the trick where you jump battery to black at the voltage regulator...and it still is driving the voltage too high.
Thanks,
Ray

[zipster]

Turns out my DVM battery was bad. Shame.

[gregforesi]

No fair solving your own problem with a simple fix.
Unusual for a battery to put out such a high voltage on its own though. I have to wonder if it went bad due to the overcharging.
The rectifier just cuts out the negative part of the voltage coming from the three phase AC stator so the answer to "does it affect charging voltage" is no. The voltage out of the rectifier is dependant on engine rpm and can (should) be as high as 25 volts (1/2 of the 50 volt AC max stator output). The regulator then knocks that down to 14.25 or so for the DC side of the system.
The caveat here is "...what Greg doesn't know about electricity fills libraries." - Dr. Hoppe PhD EE

[zipster]

Yeah, when these digital volt meters go bad they read high. I'm presently chasing demons related to converting my turn signals to LED, so when they stopped working I assumed high voltage had burned them up.

[gregforesi]

I just noticed the scooters in your signature. When you get a chance, post a picture of the Lambretta.

[OhioBill]

I have a question along the same line. Sunday while coming off the highwway my digital voltmeter shot up to 17 volts. First time ever that high, normal is 14.6 . Return trip it stayed at 14.6. Is this a prelude to my regulator going bad? Glass mat battery.

[CYBORG]

17v for any length of time will fry the battery. I would check all my connections in the charging circuit for corrosion/ or loose connectors . Also the battery connections and frame ground