ok here goes. the breaks are triggered by the brake lights but draw power from the sidelight circuit. the most common controller i fitted was elecbrakes out of australia. you can get a lead that plugs between car and caravan and its plug and play or get an auto sparky to alter the trailer wiring for you. takes 30 minutes.
the breakaway cable can trigger the electric brakes but yes there is a standalone batter in the van to do this.
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