Battery charging issues - YBR125

[sabian92]

Hey,

I posted a while back about the battery not charging - replaced it and thought all was well. I've replaced the headlight bulb with a brighter bulb but the same wattage (35w) so that shouldn't be an issue.

The engine runs rough at idle (rev needle jumps up and down) and on occasion cuts out. The electric start doesn't work most of the time unless it's been running for a good 10 minutes before. Multiple starts in a short period of time are impossible - kickstart is a lifesaver! I've got heated grips but I don't use them as it's not cold enough but with them on the battery doesn't charge at all.

Obviously it's an issue with the charging system but I can't work out what from the Haynes manual I've got. Any ideas?

[moonzoomer]

Have you checked the reg/rec for good connections and operation , also check the sidestand switch for good operation and connections as these can cause problems with engine running but are unlikely to have an effect on charging. I would also suggest you disconnect the heated grip circuit from the battery just to prove it is not the cause of the problem.

[Islander]

Measure the voltage at the battery terminals with no engine running and the ignition off, With a good battery you should see 12.5v ish. Now run the engine and measure again. You should see a slightly higher voltage rising to around 14v as the engine is revved to around 4-5k.

If the initial voltage is low then the battery is stuffed. If the voltage doesn't rise when you rev the engine then the charging system isn't working properly.