well if you do decide to replace with another electric setup, definitely look at the CFM ratings for the fans. Basically the higher the CFM the more air it pushes through.
Also when you reinstall the new electric ones, use a high amperage relay and put a fuse on the hot side so that you can insure the electric fans will be able pull enough current. I think some people try to splice electric fans into existing wiring, but the correct way to do it is to use a properly gauged wire with a relay.
It sounds like who ever installed your previous fans that failed did it incorrectly, the fans pulled too much current and fried the existing wiring because they were too small(thin).
Do it right and run thicker wires with a relay, and you shouldn't run into this problem again.