Hi Wuming. A lot of us here have used this power supply for our GPS's, but I would be apprehensive about using it for a greater wattage.
I personally use a relay powered from the rear brake circuit to supply all of my ancilliaries. This keeps the system relatively inclutteres and simple. It gives me the opportunity to add on more 'bits' and is cheap to make.

Search on 'Relay' to find details and pics.

The main reason that I did it this way is that the wire to the aforementioned connector is very small and compared to the wires for my heated jacket is well out of proportion. The last thing I want is to melt any cables within the loom.

Hope this helps

SteveD

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