Help needed on Koso

[Trojan]

If its been covered my apologies... I have a Koso Rev counter Analogue type with FOUR wires coming from the gauge RED BLACK WHITE have all been sorted but a little apprehensive about the brown??? it states DC12V MAIN POWER SWITCH on manual, now im no sparky but it does say later on NOT TO BE IN PARALLEL TO BATTERY so any suggestions as to what wire would be the best GREEN ??? all my set up is BGM 120W STATOR RECTIFYER THAT CAN TAKE A BATTERY FEED IN THE CENTER, so obviously thats where all the supply is coming from as its a FIVE PIN TYPE .....thanks in advance chaps ..hopefully this will get me on the road shortly........