I use a Y harness and 2 -2cell lipos. Have been for 4 years on the same box. No issues so far. Since its under load 99% of the time, free wheeling speed is not an issue. Also, at a higher voltage, the current draw goes down so it runs cooler. And considering it runs for seconds at a time are all reasons its lasted. That said, I wouldnt even consider higher than this...