Battery dying

[Jonas]

Hi,
So I've checked my charging system and seem to get over 14 volts at the battery when it's revved over 3000. But, after prolonged riding the battery slowly goes dead. I check the alternator, checked the regulator/rectifier. Everything seems to be working fine. But, I went out for a ride with my wife (it's her bike) and on the way back it died on her. I jumped it from my bike, but once I took the jumper cables off it immediately died, unless it was revved over 3000. So, she rode it home revving the whole way and looking a little crazy. I'm at a loss of what to do now. The battery doesn't seem to lose voltage when turned off. Just when riding. Any idea of any tests I can do to check?
Thanks.

 

[mrtwowheel]

Canada, here in the states we can have our batteries checked for free with no obligation at automotive stores. You should do the same regardless of the batteries age. That's just the starting point.

 

[Jonas]

That's a good idea. I'll look around. It's done this to multiple batteries, though. It's fresh in the spring and a month later it's dying on her again.

 

[Signal]

Do you have a stock charging system, and what is your ignition system.

 

[Jonas]

Charging and ignition are stock, I believe. Someone before me chopped up the wiring a bit though. It's got three blade fuses loose under the seat.

 

[Its been a long time]

Charging and ignition are stock, I believe. Someone before me chopped up the wiring a bit though. It's got three blade fuses loose under the seat.

What year bike? There's excellent guides in the forum to assist in checking the condition of the charging system. Depending on the year the systems work a bit differently before and after 1980. The stock system is very good once it's set up with modern rectifier and regulator.

 

[650Skull]

Could also b a loss of volts going through the ignition switch. Regulator would think the battery wasn't charged. If so the regulator would b charging the battery when it didn't need it.

 

[FB71]

Check for AC voltage on the charging system. A failed rectifier diode will leak AC, and that will discharge a battery, even if there's sufficient DC voltage in conjunction. Max AC leakage should be less than 0.5v.

 

[Jonas]

The bike's an 84. All the checks I've done on the charging system have come back positive, which is why I'm so frustrated. I checked diodes on the regulator/rectifer (but will look for AC leakage next) and checked the voltage at the batteries, which seems to check out as well. That's why I'm assuming it's leaking somewhere. I'll check the ignition switch as well.

 

[Jan_P]

If it is a stock mechanical regulator it can be a problem
A voltmeter installed on the bike would be a good thing at least temporarily for fault finding
Something can short out when hot only

 

[Jonas]

If it is a stock mechanical regulator it can be a problem
A voltmeter installed on the bike would be a good thing at least temporarily for fault finding
Something can short out when hot only

That would make sense, as it seems to drain faster when we're putting the engine under high load for longer periods of time.