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Regulator Voltage

Jed

Joined Mar 2003
8 Posts | 0+
Blackfoot, Idaho USA
My 2002 FX 470 has had a harder time starting with the battery. I charge the battery and it spins fast and starts. After an afternoon ride it is difficult to spin engine. The battery is new. I tested the voltage at the battery terminals and it reads 12.1 volts and the same when the engine is at high idle. What should the Voltage be at mid rpm? Could I have a bad regulator?

Thanks
 
I am not sure about the bike, but I am an electrian "residential" and I do almost all of the work on my farm tractors. A 12 volt system should generally have 12.7 volts on a fully charged battery. If it is less than about 12.5, then there is a problem somewhere. When a voltage regulator works like it should on other equipment, like one of my tractors, at a higher idle or midrange rpm the votlage should increase to around 14.4 to 14.7 volts. If it reads more than that, you are overcharging the system and burning your battery up. The battery will get too hot and boil the juice out of it. If your voltage doesn't increase at all when the bike it running, I would check the obvious first. Check all conections and check wires for possible breaks. Then go from there to the more complex issues. Good luck.

Jay
 
14.4-14.7V is a bit high & will boil a battery if it is held at that voltage too long. Generally 14.1 to 14.2V is about right. The way they seem to test the state of charge on the sealed batteries in these bikes is to accurately measure the terminal voltage at rest. A full charged battery should show about 12.6 volts - I'll check the table at home to be sure. 12.1 volts indicates your bike isn't charging at all. Likely fault is a wire off somewhere or a crook rectifier. A crook regulator will tend to let the voltage go high & overcharge the battery rather than not charge at all.
 
The reason I said that I wasn't sure about the bike is because mine is kick only. 14 volts on the high side of the charge is fine, but the 14.6 or 14.7 will not boil a full size 12 volt battery. Though is might upset the small bike battery. I still would say it would be fine as long as it is not above that. I say this because I have fixed several farm tractors and all of them call for between 14 and 14.6 volts per service manuals on the high side charge. Maybe someone could be of a little more help and check the voltage on their charging system for you. Brad and I will just have to agree to disagree on the high side voltage, but that's fine with me. I am not trying to argue with with him.

Jay
 

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