Hey everyone,
I just recently bought a 05 rebel cmx250c, and have been doing some work on it. I'm having a possible issue with the charging system.
When I charge up the battery to 12-13 volts and put it on, the bike will start right away. While the bike is running I measured the voltage on the Battery runs steady at 7.5-7.8 volts.
Is this an issue with the charging system or a bad battery?
I just got the bike, so I'm tracking down all the bugs. Any help would be appreciated
Welcome. Sounds like a bad battery to me. Measure the voltage at the battery with the engine revved and see what you get. Like many motorcycle electrical systems, the charging system barely breaks even, if that, when idling.
You can also take the battery to many auto supply stores and have them do a load test.
Motocross and Yuasa batteries are very high quality and last a long time with normal care. Yours takes an AGM type battery.
another 'easy' test...disconnect the battery negative terminal while the bike is running, and measure the voltage across the wires (not the battery) and see if the charging system is delivering 13-ish volts...
Well, I'm not sure that I agree with the majority here in this case. It could be a bad battery, but if it was that bad, I doubt that it would have cranked the bike.
I agree that the battery needs testing to determine if it is bad or just needs more charging.
One test is to charge it fully overnight on a trickle charger or other automatically controlled charger that won't overcharge the battery. Then remove the charger and check that the voltage remains at least 12.6 volts or higher. If it falls quickly to 12.0 or less voltage, then take it somewhere to have it professionally charged and tested, but be prepared to buy a new one since it is likely dead.
Another test is to charge it, then use it to crank the bike, and measure the running voltage. If still reading 7-8 volts, then stop the bike and measure the voltage. If it stays at 7-8 volts with the bike and all lights off, then the battery is bad. If it recovers to 12+ volts, then your alternator is probably not charging enough and the lights are dragging the battery down. If revving the engine does not increase the voltage to 13+ volts, then you probably have alternator, regulator, or something else going bad in the charging system.
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