What "direction" to I wire the breaker between the batteries and charge controller? Do I put the controller on the line or the load? Presumably power flows in both direction, which I read is unsafe for DC breaker... but this application seems very common. I am using a 100/20 MPPT with a BlueSea Series A 25A breaker.
My guess is that the batteries go on the load side because a majority of the power flows from the controller to the batteries, but that wouldn't account for nighttime when the batteries are powering the controller.
I primarily want a breaker so I can easily disconnect the controller when not in use to avoid unneeded draw.