My battery died..

The only thing they clean is where the fan is. That blocks airflow to the battery. When the battery gets hot its output is limited first along with degradation of life. The stuff in the ECUs can easily take 85C all day long, you'd be dead. The part where "transistors and diodes" will blow up is under the hood in the inverter. The IGBTs in there are liquid cooled and less-than-stellar cooling on the G3 (Toyota skimped after building the tank that is the Gen-2). If your inverter coolant pump fails and it doesn't cool, the inverter will get hot and limit its output as its life is degraded. Then the car will just shut off and refuse to move because it is too hot. Having the inverter blow up would be super catastrophic failure I've never heard of.