right the feed that comes from the split charge goes to two battery kill switches, breaking the live feed to both batteries respectively, the sensor wire for the split charge that tells it when to charge was reconnected to the split charge instead of battery, to charge either battery i choose which kill switch is connected, simples. i always make sure there is a t least one battery taking a charge and i dont change them whilst engine is running, this way i can leave the fridge battery running the fridge and recharge every 4 days or so, i know it can do this because i've it here without starting it for longer than that without a problem, this leaves the third battery to run everything else,spotlights, inverter, compressor,horn, etc. also what i've done is any feeds that were taken from either battery i've run the pos and neg back to both each respective battery, so when its not on a charge cycle it draws only from battery and can't create a circuit via the earth. hope this makes sense.