battery elimination

[mysta2]

I'm still figuring out how these old bikes work, and I keep seeing race bikes without batteries, (vintage 60's - 70's cafe racer types) and I just came across a battery elimination kit (no explanation, just a photo of a small cylindrical thing)... how does this work. What does the battery really do on a kickstart bike?

[niterider]

The ignition system would have to be somewhat like that of a lawn mower, run off of a magnito. And tha battery on a kick start bike helps the generator run the lighting system at low idle. I don't know any thing about the cylinder thing you talked about.

[flynrider]

I've seen these kits. They are for simple bikes with no electrical system. That big cylinder thing is a large capacitor that holds a small charge of electricity. Just enough to run the ignition system long enough to kickstart the bike. Once started, a generator (alternator will not work) can recharge the capacitor for the next start. These things are designed primarily for race bike to save the weight of a battery. I've seen a couple of folks try it on street bikes with little success.

[BuzZz]

Aside from being a stable resevior of electricity for your lights and ignition, the battery acts to eliminate the spikes and dips of the generator/alt output, giving a nice, consistant wave-form of elecrical current to anything that uses it on the bike.

[Aggroton]

the couple indian larry bikes ive seen use magnetos and not batteries....

[flynrider]

Magnetos will work, but they complicate matters somewhat. You have to figure out a way to drive the magneto, plus magnetos with variable timing can get quite pricey. On a street bike, you're still left with the problem of lighting.

My plane's engine uses magnetos for ignition, but has an entirely separate electrical system (alternator, batt., etc...) for everything else. The beauty of it is that a complete electrical system failure doesn't affect the engine one bit.

[mydlyfkryzis]

The bikes with permanent magnet type alterantors can work with these. These type systems (my CB360t has a PM alternator, my NH750 doesn't) use a zener diode to regulate the voltage. Since the permanent magnets are not "controlled", the faster the engine turns, the more they put out. The zener diode just shorts to ground anything over 15.6 volts.

The battery on my CB360t does 2 things. It supplies stored voltage to start the bike and then acts as a reference for the zener diode. Without the battery, the zener diode would not know when to shunt the excess voltage to ground. The battery ellimantor kit, as described above, provides the reference voltage for the regulator. It does not supply the starting motor voltage, so kick start is the only way (or push start) to get the motor going.

A PM magnet alternator provides just barely enough current to provide a spark with the points/coil system when you have dead battery. I would believe a bike like my CB360t would be troublesome to start without a battery as it is definitely a PITA when the battery is dead. (But it will start)

A magneto system is a little different then this and wouldn't need the battery eliminator kit as it is designed to provide a spark with a constant voltage source like a points coil system.

[flynrider]

You are correct, Richard. When I posted that alternators won't work, I was thinking of the more modern ones with external excitement of the primary field. A permanent magnet alternator should work as well as a permanent magnet generator. That is, not extremely well. The downside of those alternators and generators was that they didn't generate much power at low rpms.

[BuzZz]

Even with a magneto, you need a battery and some way to charge it to run everything else that draws electricity. Even if you did get a mag mounted and timed correctly, they ain't cheap and tend to failure. Sudden failure, no warning. Aircraft must run redundant systems for a reason.

I wouldn't want to even try converting a bike to mag ignition if there was anyway to run an alternator. I don't need the headache....

[kar_the_terrible]

Yeah I had a magneto run scooter and my uncle had a motorcycle. Buzz is right in the fact that it provides a stable power source. Essentially your battery acts as a ballast for the varying power that comes out of the alternator.

So on non-battery bikes you'll notice that the headlight and taillights dim considerably when on low idle. Also you wont be able to have too many running lights and such. In other words, with the way people drive out there, you probably will *never* want to take this bike out at night and stop at a traffic light.

However, that said. eliminating the battery also takes a bunch of junk out of your electrical system that will make diagnosing probs even more easier