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Can a bike run without a battery?

33K views 12 replies 5 participants last post by  reflectedstatic 
#1 ·
I apologize in advance. This is a question about my wife's V-Star. It's been hard to start lately. The battery is obviously weak. We hadn't ridden for a while because it's been too friggin' hot. I start it weekly. It cranks slowly buy eventually catches and fires. I took it out yesterday and it died several times. Felt like it was starving at higher rev's then died at stop signs. I had to leave the key off for about five minutes before it had enough juice to start, I eventually got it home and let it idle for a bit in the garage. After that it would start instantly. Bad battery? I thought that once it was running you could pull the battery out. Of course...I guess the headlight/tail light/brake light might be a factor.

Thanks in advance.


Cheers,

SK
 
#5 ·
Just drag the battery to a chain auto parts store, get them to hook it to the machine, and they should be able to tell you pretty quickly if something major is wrong with it. If it's not that, check the voltage regulator, since most dead alternators are actually dead voltage regulators. If it's not that, start to look elsewhere.

To answer your question though, in theory, it is not necessary to have a battery in an alternator-powered electrical system once the engine is running. The battery is absolutely necessary to power the field windings while the engine is starting, which is why you can't bump or kick start a bike with an alternator if it has a dead battery, but IF there's never more current drawn than is being produced, a battery is not strictly necessary once the engine is running. That's a big 'if', though, because most bikes' alternators don't keep up with current draw at low RPMs, making a battery necessary to fill in the gaps.

Of course, if the battery has an internal short, all bets are off.
 
#8 ·
To answer your question though, in theory, it is not necessary to have a battery in an alternator-powered electrical system once the engine is running.
That all depends how the system is set up. On most bikes these days, the battery is part of the circuit such that the bike won't run without it, whether under minimal load, lights off, disconnected once running or whatever. As you say - a shorted battery certainly won't work.
 
#6 ·
Battery

My exp has been NO the bike will not run w/o a battery or w/ a dead one! I GUESS if you could kill the lights & all it might run if its warmed up, but forget pop starting it! Just bought a cheap little 150 Chinese scoot to get to the Bonne garage. 1 thing I really like @ it IS- the headlights etc wont work unless the scoot is running! MAkes starting a bit easier w/ a soso battery! As said MAGNETO!!!
 
#7 ·
I love this forum!

I just wanted to thank everyone who responded. Now all I need to do is FIND the battery and then it's off to Auto Zone.


Cheers,

SK
 
#10 ·
Yes indeed - the older stuff was set up such that the electrickery generator could power the whole system. I assume that was because batteries were still a bit iffy in those days - or maybe that's just how they felt like doing it at the time. :D
 
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