atrflyguy, one of the reasons for APU starter limitations is the load on the battery, not just the electric starter unit. One of our horror displays for the 747 was an APU battery where the starter limits had been ignored. For the Classic 747, the heat generated by a start was quite intense. Ignoring the limitations caused a complete battery metdown- the casing melted as well. I would think it is not different for the 737, so it is not just starter unit heat that is the problem.