Bonneville America Forums Forums Technical Forums General Tech battery/alternator question

should the alternator be powerful enough to keep the bike running if I disconnect the battery while its running?

Yes it will but don't do it. Without the battery in the loop, there is the potential for the voltage to spike and fry your electrical components. In simple terms, the battery provides some stability to the regulator circuit.

I'd have thought so

In theory, it should kick out enough juice to run the bike and charge the battery

However, the battery is also used to absorb any spikes in output and provide extra juice when needed, eg. for indicators, brake lights etc

Also, the alternator will not give out enough power to even run the bike while the engine is just ticking over

But why would you want to do this?
If you stall, you'll be stuffed

Darn it

I've got to learn to type quicker, maybe even use two fingers

I had a dead battery, charged it up, started the bike, and disconnected on terminal to see if the alternator would keep it running to see if the alternator was bad like you would with a car. It died once I disconnected the battery. I started going through the electrical to see if there were any glaring problems and the fuse connection needed a good cleaning. now with a fully charged battery it is putting out about 14.7 volts at around 2500rpms. But it still dies if I disconnect the battery.

Jason,

Trust me, disconnecting the alternator or battery while running is not how you test the alternator on anything, bike or car. It will lead to other problems.

Put your voltmeter on the battery with the engine shut off. Measure the voltage, should be 12.6 volts. Start the bike up. If the voltage rises to 14.7 like you stated, the bike is charging fine.

Thanks,I wish I had measured it before I went and cleaned everything up. But battery holds a proper charge and the voltage changes to 14.7ish with the bike running now so it looks like I am good.
That was first time ive ever tried that on a bike, now after watching the voltage reading at different rpms I can see why the bike died when I disconnected the bike at an idle. It really did not put out much of a charge until the RPMs got over 2500 or so.
I Was taught by my mechanic Uncle way back before the cars had computers that easiest way to see if it was the battery or alternator was to disconnect the battery, if the car kept running the alternator was putting out.

dont do it .. unless your workin on an old point type system. auto.. motorcycle whatever. . a modern electronic system is not NOT designed to run w/o the battery.. you can short the ecm.. or blow the diodes out of the alternator.. unless its an old .. dodge dart or something ..quit it.. before it gets expensive..
agreed .. pulling the terminal is NOT a batery test for anything that does not have points.. regardless of the number of wheels ..