overcharging issues

A little background: My bike seems like a shoe-in for corrosion in voltage regulator wiring. The battery wouldn't hold charge no matter what, so I checked the charging system. At 2000 rpm, and higher the voltage at the battery holds at around 17.5v. Jumped from a car battery the bike starts right up. I'm going to clean the contacts and go from there. What are the chances that I'll need a new R/R unit? There is one on ebay for about $35 shipped, should I be bidding?

Also, is it possible to find Yuasa or other applicable batteries at a major auto supply chain? Thanks guys.

 

While you're checking the charging system also check the battery fluid level (if it's a maintance type).

The car wasn't running was it?

35$ sounds good to me but I've never bid on one... never hurts to have a spare. Problem with used spares is you don't know how long they'll live either.

 

The battery fluid level was fine, I checked that first. In any case, whatever condition the batter was in, it shouldn't be charging at 17v when the alternator is going.

First time (a couple of days ago) I was stupid and the car was running. Now I know better, so when I jumped it yesterday I left the car off. At least I didn't take the battery out.

 

Split-open the plastic quick connection attaching the Voltage Regulator to the Wiring Harness.

Look for evidence of the wires having had a heavy load melt the connection around the terminals inside the connection clip; particularily the RED wire.

If the plastic is melted from being subject to high amps passing through that connector ... the Regulator got cooked.

Check the Alternator Brushes; too.

 

So, what exactly happens if you jump your bike from a running car? I haven't done it, but I'd like to know why not to do it in the future.

 

What happens is you're feeding 60 amps into a tiny little battery with thin plates. At best you might just warp the plates. At worst you'll get to see what the plates look like up close.

 

The electrical system on the bike is rated for 15 Amps. A running car's alternator, particularly one with sound system amplifiers, plus a full load of electrically operated creature comforts, can easily triple or quadruple that output > at idle!

All those high amps, getting crowded together, along the narrow-gauged wiring on the motorcycle's wire harness, finds resistance's at points where mechanical, quick-connecting, splices are added to facilitate assembly ... and the wiring heats-up - fast.

What also heats up as fast, are the soldered connections of transistors, diodes and junctions on Integrated Circuits. Those connections melt and become OPEN, or cannot handle the surge and become destroyed.

Twenty-five years ago ... with roll-up windows and a AM-FM tuner; the car's output was about the same as the bike's.

Twenty-five years later ... it's a different story.

 

I hear what you all are saying but I think there is some confusion about jumping from a running car. The electrical system on the motorcycle will only handle up to 30 amps so I can totally understand the desire to avoid pumping more through it. The key here is that the bike's system will only pull what it needs out of the other source, be it just a battery or a running car. The trick of the running car is to hook up the bike to the car without the car running. Once connection is made, then you can fire up the car. The problem with hooking up the circuit with a running vehicle is the resulting voltage/current spike that could very easily fry components in the electrical system. If the connection is made with the car turned off, the potential difference is minimized and the car can be started up safely. Remember, the bike will only pull as much current as it needs so don't worry about using a car to jump (or just a car battery). Just don't forget to have both vehicles turned off when you connect them. Hope that cleared it up.

 

Good to hear that I'm safe. Even though I never actually knew why, I never jump anything without turning off both vehicles. Someone somewhere must have told me not to do that.

 

Thanks for the info guys. I'll have to remember this, in case I ever get my XJ running consistently again.