MTFCA Forum

Home depot has these small 12V batteries for emergency trailer brakes, house alarms, etc. I would like to use one to power a tail/brake light. Can I use it as battery power to start the engine or is 12V too much?

12 volts is not too much, the mag can put out 18 volts so there is lots to spare, I use dry cells.

It won't turn the starter if that's what you're asking, but it will power the coils for crank starting, then switch to mag. You could probably do a full days touring with it running on battery even. The coils don't draw that much.

Jon

more importantly is the question: "Where does the battery attach to?"

do you know for certain where it attaches?

There are 8 insulated posts on the coil box that deal with timer and plug wires. Then there are two lower insulated posts which deal with current sources (battery or magneto). One post should have a wire running from the top of the transmission hog's head to the post. The other post should have no wire on it and if nothing is botched up, that is the one for the battery (lower corner of coil box on passenger's side). DO NOT DO ANYTHING WHICH WILL SEND BATTERY CURRENT DOWN TO THE MAGNETO POST ON THE HOG'S HEAD.

I have used a 12volt motorcycle battery temporarily for a while before getting a proper one for lights and cranking. It is close to the size of the trailer battery but with a lot of cranking power. It is the -Bike Master lithium ion battery DLFP20HL-BS. 12.8 volts and 500 A cranking amps. Look it up under bikemaster.com. I am not suggesting it may be the one you are absolutely looking for, but you could look and see if it may or not suit your needs. Frank

I use a 12 volt Duracell in both of my '13s. The touring has one under the back seat, and the roadster has on in the tool box in back of the gas tank. They are the size of a Model T coil, and are rechargeable.