Topic: CB650 Charging System

[Nate]

I searched through the forums to look for a similar issue with no avail.

Here's what i have.

Battery didn't seem to hold a charge. After riding for a couple hours the bike would have enough juice to start the bike for the next 8-12 hours. After that the battery would test out at around 11volts. So i replaced the battery with a new one. Set it up and charged it according to manufacturers instructions.

The new battery seemed to solve the problem. Voltage stayed in the 12.5v -13v range when the bike was off. After about two weeks i started having the same problem. So i started trouble shooting to see what i could determine.

When the bike is running at idle i was getting around 13.5v at the battery

The voltage would progressively rise adding more rpm's to the engine topping out at around 14.5v

After turning the bike off the battery voltage would drop to under 12v.

Everything in my mind says battery issues, but it's a new battery???  Am i a complete idiot? Am i missing something obvious?

Thanks for any guidance on where to go from here.

[supersport_CB400F]

I had the same sort of problem with a new KOYO battery it just drained all the time, flat from full charge in two days, I thought I had a short in the wires….bought a new VARTA battery and the problem has gone so you can get bad new batteries! What bugger that was I wasted days looking for a fault that didn’t exist.

[Nate]

VARTA? Is that a sealed or old style battery?

[supersport_CB400F]

VARTA? Is that a sealed or old style battery?

I got a lead/acid (old style) but I'm sure they also do a no maintenance version; I went to the VARTA franchise in my city. Check the website for options http://www.varta.com/eng/…… if the battery is good enough for a BMW it’s good for my Honda. 

[oldfart]

VARTA? Is that a sealed or old style battery?

German or summit like it.  Used to come in BMWs.

[750goes]

start with a fully charged battery and measure these voltages

1 motor off/ignition off - voltage across battery terminals
2 motor off/ignition on - voltage across battery terminals
3 motor on and headlight off
measure the voltage at 1000 rpm, 2000rpm, 3000rpm, 4000rpm  (hold the revs for 15 seconds at each rpm or get a maximum reading)
4 motor on headlight on
measure the voltage at 1000 rpm, 2000rpm, 3000rpm, 4000rpm  (hold the revs for 15 seconds at each rpm or get a maximum reading)
 5. motor off/ignition off - voltage across battery terminals

what are the readings


and from what you initially describe it sounds like you have a short in the wiring somewhere..

[oldfart]

Here's a good method.  Even though labeled "DOHC" the system is correct for the CB650 because the 650 has the identical system to the bigger fours. 

http://home.earthlink.net/~trinomial/DOHCcharge.html

[Nate]

Thanks for all the direction. I'll have to spend some time on troubleshooting. 

Wish me luck

[Pinhead]

Your rectifier diodes could be leaking current... Read the post in my sig.