split charge relay wire

Hello, What size wire (AWG) would you recommend to use with a split charge relay? Thanks

I really have no idea what you are asking, nor do we have enough info to help you, but just to be safe, the same size as the original charge wire.

LOL! Not a splitter that charges one battery before the other, or monitors, and regulates... etc etc. I use an ordinary relay. (Which is triggered by the charge lamp, else a voltage circuit could be used - but that has complications, and expense.) If the 2nd battery is only charging, then size the wire for the maximum charge you expect. That depends on battery size & type eg, my 40AH AGM after cranking charges at 40A dropping to under 10A within 1 minute.) If the 2nd battery is also supplying a load, then add the load current to the above. Take into account voltage drops along the cable's length (only important for loads; it's not critical for charging only (because as current drops, so too the voltage drop)). But hence why cable sizing generally reflects the load since the long term battery current will only be a few amps.    And don't forget to fuse EACH end near each battery. I recommend self resetting circuit breakers due to the often high initial current.