Topic: still having charging issues...its a mystery

[markiemark]

Hi all,

I went on my road trip up to Monerey, CA from Southern CA.  About 400 miles each way.  She ran perfect all the way up, then on the second day, I was cruising around town, and I lost power, and it died at a stop.  I was able to kick start it and get it back my friends house where we were able to charge it (thank god I decided to bring my battery tender plus!).  After a full overnight charge, she ran fine all the way home the other 400 or so miles.

So since I got my '73 cb500 back in april, I've had issues with the electrical and charging of the bike.  I've posted questions, checked stuff, and haven't found a whole lot wrong.  I bought a new battery pretty much right away as the old one didn't seem to hold a charge.  That worked for a while. I bought the battery tender as I mainly drive in the city to and from work and rarely get up to 5000 rpm's for any considerable amount of time, and I usually hook the tender up every night. (It's the kind that when it gets to a full charge, it floats and doesn't overcharge)  Blew a fuse, turns out the rectifier was shot so had that replaced.  Blew another fuse 6 weeks later replaced old tube style fuse with more modern blade type (as per suggestions on this forum). 

Would that kind of power loss be considered normal for these old bikes?  I would think not, but i am not sure...

Any help, suggestions, thoughts??

Thanks

[Gordon]

That's definitely not normal.  With the battery fully charged and able to hold its charge when a load is placed on it, test the voltage at idle, and then test it while revving at around 4K.  The voltage should increase to around 14.5. 

[TwoTired]

Probably should consider the load placed on the system.  Has it changed from stock (new coils, brighter headlight, coffee warmer, beer cooler, etc.).

Make sure none of the stator wires are open w.r.t. each other or shorted to the engine case. (Can check this at the rectifier's harness plug.)

Find out if, while in operation, the Vreg is getting full battery voltage (Black wire), or if system drops are reducing power to the Vreg/Field coil.

Wouldn't hurt to verify the field coil winding resistance ~ 4.9Ω

Remember, in a pinch, turn off the headlight to save 4-5 amps battery drain or charging system loss.

Certainly RPMs at or near idle mean the alternator can't keep up with full system load, so the battery depletes.
You could learn at what RPM this occurs by making an RPM vs Battery voltage chart.  The battery will begin to increase voltage when the charging system takes over the power distribution duties.  Best to measure this when the battery is at full charge, though.

Cheers,

[markiemark]

So the load weight matters?  I didn't realize that.  I failed to mention (because I didn't know it mattered) that when it died I had a friend riding on the back (a full grown 180lb man).  I just took him around a couple blocks and that is when it died.  So could the extra weight have been an issue?  But what if I want to go on a road trip with my lady one day??! (she's not 180lbs by the way...lol)

[markiemark]

Oh and as far as I know the bike is completely original, except for the bassani pipes, no beer coolers lol, and been mostly in a garage since the 70's.  When I bought the thing it only had 3900 miles on it. 

[Gordon]

He's talking about the load on the electrical system.  Do you have any "upgrades" like an H4 headlight, electronic ignition, small kitchen appliances, etc? 

[TwoTired]

So the load weight matters? 

no, not really....Electrical load.  As in, you plugged in too many toasters to the same outlet.   ...Poof!

It canna take the load Captain, it's gonna blow!!!

[number13]

Remove the electrical panel, it's easy, and have a look at the
wiring. That part is exposed to the elements and just hidden
enough that you wouldn't ordinarily think to look there. I had the same charging troubles
on my 500 and found the main red wire was corroded down to just a few strands.