Anyone use a battery isolator on a dual battery drag car

I was reading that a relay type isolator does not suffer from these diode problems. These type simply disconnect the isolated starting battery. When the engine is started, a 12 volt ignition trigger wire
Rejoins the two batteries together to function as a normal two battery parallel system. Any thoughts on this?

That is what I always used to use, another word is "continuous duty solenoid." Looks something like a Ford/AMC fender mount solenoid, but designed to be "on" continuous. Another thing you could do if you are just manually charging it, is just use a disconnect switch to jumper them together.

The really best way is to use two chargers. That way neither battery will try and pull the other and the chargers can properly sense voltage Whichever battery is your starter battery will undoubtedly be "down" in relation to the other through a race weekend