Sunday, August 21, 2011

Voltage Regulation

... or lack of voltage regulation as the case is.  The alternator actually works too well.  I bought this cheap regulator/rectifier intended for scooters.  Its voltage stability is horrendous.  Naturally the Permanent Magnet alternator increases in voltage and frequency as I rev the S7 Deluxe engine.  The regulator should compensate for this and keep the voltage around 6.x volts and not too high such as the 7.x volts that I saw this morning.  At highway revs the ammeter was reading nearly full scale of 8 amps!  "That's WAY TOO much current", I said to myself as I sat beside the road this morning.  The voltage kept going up with the revs... its supposed to be regulated to limit the voltage so that the battery won't get overcharged.  Well, the reason I was sitting beside the road this morning was that the battery WAS being overcharged and had blown the 7.5 Amp fuse that I had installed in series with it.  I was trundling along until I dropped the revs and the alternator wouldn't produce enough voltage to keep the ignition going... at which time the bike stopped running at the intersection.

A quick disconnection of the stator leads and a jumper across the fuse, limped KYL95 back home to the workshop.

So, now I need to replace that cheap scooter regulator.  I imagine its just a simple series pass transistor regulator in there, and its not yielding good results.  The correct solution is to use a switching regulator.  Like this one:

Oh, and I've purchased a resettable circuit breaker too.  I HATE fuses.


  1. If it would stop raining, I could fully test the alternator conversion.

  2. Stupid surface mount stuff. Going Linear.