Dreaded White Wire - 6V 30W Spotlamp?

DuctTapedGoat

DuctTapedGoat

Active Member
I want to hook up this 6V 30W spotlight lamp up to the generator without risking burning it out with too much voltage. It's rated 7.5V .5A on the Raw 2 stroker. I'm taking the multimeter to it later this afternoon to get my motors specific output. Should I use 6V worth of resistors to prevent it from shorting out the bulb, is there another electrical component I should use instead, or will the light only take 6V and no more than that?
 
Alternators on cars actually charge the battery at roughly 13.7 vdc, so all the electronics in a car are basically designed to handle that much or more. You can reduce the voltage by either resistance in series (using Ohm's law) or with a step down transformer.
 
30W off the white wire? Seriously? It's good for 3-5 watts at the most, unless you have one with upgraded magneto.
 
1/2 watt load is enough to over tax these magnetos. I ran a Vapor Tech speed ohmmeter temporally on a china mag to see if it would work. It did but barely worked the light display. Its said to run on a 9v battery supply for up to 4 months.
 
I don't know weather or not these motors will handle it, but a 6v bulb will generally handle over 12v for a short period of time. Running higher voltage (within a reasonable range) will not short out a bulb, it will just make it really bright, and burn out sooner. My Packard still runs 6v, and the voltage regulator lets out between 6.12 and say around 7. Usually 6v generators put out around 8v depending on RPMs, and my headlights that are ran directly off the battery (fused of coarse) work fine at 8 volts. A 12 system charges at 14.7, and take, for example, a test light that uses an 1157 12v bulb; it does not burn out when testing if an alternator is putting out.

On a side note, 6v systems demand a MUCH HIGHER amperage. A 6v headlamp usually runs at least 30A, and some use up to 50A. Something with that kind of draw would almost definitely kill the motor. Perhaps you should try something that uses a 6v maglight bulb? Im pretty sure those don't use much amperage....

Anyhow, let me know what you discover. I've been wondering if the gens on these things put out ok or not. Good luck, man!!
 
Pick up a 6v SLA battery at the hardware store, They run about 18 bucks, I think mine is rated for 4 amp hours. They are the batts used in emergency lighting. A simple charging circuit with about 5 dollars worth of parts from the Shack and you should be able to poweryour spot light with the white wire. The batt will also help smooth out the current so the light does not pulse with the RPMs of the engine.
 
7 and a half volts at half an amp is less than 4 watts.

If you connect a 30 watt bulb to it your motor won't run.
 
.5A 7v max.. That is only around 3.5 watts. And since the winding for this shares the mag winding.. anything larger will hurt if not kill the spark.
 
Within half an hour I realized that it wouldn't work - where I'm at now is thinking how to supplement the power that is there via rewound roller generators, ac/dc inverters, battery packs, 12v magneto addin etc.

It's easy enough to say it won't work - but does anyone have constructive input as far as how to get it to work?
 
You can charge a 6 volt battery with 7.5 volts. Make sure to install a full wave bridge rectifier between the coil and the battery or the battery will fry the coil.

Battery will not charge if the 30 watt light is on though, just when you are running and the light is off.
 
To see with and to be seen - safety, I ride in some rural areas, which has some horrid road conditions and people driving 20 miles over the speed limit at night. It's a spotlamp that was used for coyote hunting, which I figure would be perfect for me.
 
Yeah, riding a bike at night on a country road would scare me.

Enough that I probably wouldn't do it.

Yeah it could work. You may have to add some series resistance too if the motor dies. As long as you have the rectifier in there the battery won't back drive the coil and fry it. The coil puts out AC, so the full wave bridge will get both sides of it.
 
I try not to, but sometimes it's unavoidable, and I would like to be prepared.

Ah, nice - I'm going to have to jump on making a diagram and locating parts then! Thanks Mike! :D
 
One of my other projects (it does not work yet on hold till my bike is ready for riding) is a small two stroke generator. It is a weed wacker engine attached to an old electric chain saw motor. I don't have much hope of it being useful for much, but it is small and portable it will easily fit on a rear rack. So a similiar idea might be used to give you enough pwer to light your bike up like a christmas tree.
 
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