I assume that you want to use the power lead from the MH to charge/maintain the battery on the toad.
If so, you would connect the power line (Black in above diagram) to the positive terminal of your toad's battery. I highly recommend a fuse, a current limiter, and a diode be used to protect the circuit.
Diode is installed to prevent reverse flow from the toad to the MH. Current limiter keeps from blowing the fuse if you try to draw too much current - for example, trying to start the toad engine while connected to the MH.
I use a simple current limiter made of 2 60 watt headlight bulbs in parallel. It limits the current to about 10 amps.
2008 Itasca Meridian 37H & 2015 Flagstaff T12RBST
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Yellowstone Lake 6-1-2012