I'm working on designing my cooling loop. The idea is to control flow via two solenoids to control flow to the original heater core when cold, and to the batteries to warm them on cold days, or bypass these for ordinary cooling. The "battery valve" in the diagram is a 2 way solenoid driven switch, sourcing coolant either from the coolant heater path or not, depending on whether the battery is below ideal temp. Here is a quick, dirty, terrible diagram. My question is am I off base, #1, and #2, what solutions are out there for the coolant heater I've indicated with a question mark below.