Charging Toad battery with 4-wire harness?

Here is how it Can work. Install a 12 volt tail light bulb somewhere under the hood and in series with your wire. The bulb will limit the current to the battery and supply enough to keep it up. As the toad battery gets closer to being full the bulb will dim or go completely dark.

I have done this as a poor mans trik-l-start between two battery banks in a previous MH. The Invisibrake toad brake uses the tail light wire to tap off about 2 amps. I have not opened it to see how it restricts current but a bulb is a cheap and easy solution.