A coolant system and method of operating the coolant system for a vehicle having a battery pack is disclosed. A method may include detecting a mountain grade descent condition; detecting a battery limit condition; and, if the mountain grade descent condition and the battery limit condition are detected, activating a coolant heater and a coolant pump to thereby accomplish an electric load shed. A method may include detecting a fuel cell stack warm up condition; and, if the fuel cell stack warm up condition is detected, activating a fuel cell coolant heater, a cabin coolant heater and a pump, and directing a coolant flowing through the cabin coolant heater through the fuel cell coolant heater and through a fuel cell stack to thereby warm the fuel cell stack.