My batteries overheated after a 13 hour drive on a hot day (approx 98F) and again after an 8 hour drive in similar conditions another day. Relatively flat terrain, but a two hour traffic jam the first time. I couldn't tell when the warning code occurred, because I had the beeper turned off. I cleared the code both times, but never could put a finger on exactly what caused it. The battery compartment is pretty well sealed, no vents, and the engine exhaust muffler is nearby, so I can see how they would get hot, but don't know what to do about it. Was running genny and both roof airs when it occurred. After the second occurrence, I didn't run jenny or airs and problem did not reoccur. Can't figure logic why that would have made difference though.