76 XL250 Charging question

Its a 6 volt system, I know that much. I also know that the batteries in these act as a voltage soak (or something) to help regulate and absorb excess voltage. I was doing some testing, and at the plug for the battery Im getting 3 volts at idle, and it had gotten up to 20+ volts before I got to 4000 rpm (this was without a battery installed). Is it just me, or does that seem really high? The original regulator is hooked up, and so is the headlight. I can run it with the headlight on and it wont blow. I want to make this thing street legal, but I dont want to fry the electrics. Any insight? Thinks in advance!

Edited by Thurman95

Hi Thurman:


You're right the battery acts as a voltage sink.  The alternator coils connect to a full wave bridge (pink and yellow wires I think) and the bridge rectifier makes DC to charge the battery.  There is no regulator on the battery circuit,  The battery absorbs the high voltage and because the output of the battery is always 6.3 to 6.5 volts, the output voltage is regulated and smoothed.  The bike won't generate a charging voltage at idle and the voltage across the battery will fall to the general battery voltage...If the battery is dead, you could see 3 volts, but if the battery is good it  should be around 6 volts or a little less at idle.


With a good battery, charging will start at about 2000 rpm and the voltage across the battery terminals should be 6.5 to 7.5 volts DC or thereabouts and it should climb to 7 or 8 volts as RPMs increase.  If your voltage is low across the battery terminals it's probably because the battery is shorting the current to ground.


Without a battery connected the voltage could easily be 20 volts because there is no load.  I think your bike is fine,,,,but your battery is crap.  Is that possible?



Edited by patuca

Well there is no battery at the moment. Thanks for the reply, the bike never came with a battery and I just bought a new one, but I wanted to make sure everything seems alright before I hook it up. Thanks again!


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