Wll bike run off of the alternater?

Just a quick question. If the battery dies or falls below normal while riding is it normal for the engine to quit? With a car you can run off the alternator if the battery dies. Last week my bike died while riding and it was a bad battery.

If the battery is just discharged from leaving the lights on or something, you may be able to run on the alternator (which will also slowly charge the battery).

If the battery is defective, with a shorted cell or 2 then the alternator may not be able to deleiver the voltage since the battery is pulling it down.

If the battery has an open cell or some other disconnection, the regulator will oscillate the power such that the bike probably won't run. The battery stabilizes the voltage. And you don't want it to run that way because without the stabilization, the regulator will put out too much RMS voltage even if the average voltage is proper. This can lead to bulbs and electronics burning out.

loudhvx, Thank you for the information. It just shut down on me while riding. The battery was toast. I'm not sure if any cells shorted or not but the hydrometer said less than 25% chrge. No balls floating.

It's possible the charging system is what actually failed. To check you need to recharge the battery and measure the voltage on it while it's running.

If it has a shorted cell, it will over pump the alternator to try to force the battery voltage up to 14.5V. Sometimes the alternator/rectifiers can handle this, sometimes not.

It the battery has an OPEN cell: you can take out the whole bike's electrical system. Seriously. The battery acts like a giant filter capacitor to smooth the alternator's output into a DC voltage. Without it, you can get horrendous voltage spikes. My battery flaked out on me and I got it kick started.... got about a block and it was blowing bulbs (the warning light for a blown brake light bulb came on). Another block and it went dead and coasted to a stop. The final body count was it had blown the elctronic ignition module, brake light, turn signal, ALL the small instrument lights and the CD ignition.

If your battery shows no balls floating, what this means is that the cell is sulfated and won't hold a charge. It won't take or hold a charge. If you run only on your alternator/stator, the bike will run terrible and if the battery won't take a charge, you will likely not get far.