Here is a little tip that can make you save big money and prevent you of frying your ESC.
We frequently connect and disconnect battery packs of our vehicles. Sometimes we plug our battery packs without paying too much attention to what we do or we do it quickly while running to the track because the race starts in few seconds. Inverting the polarity can be catastrophic for any electronic speed controller and LiPo packs.
It may be really hard to clearly identify the positive pole from the negative pole on some type of LiPo packs. This is especially true for packs that use bullet type connectors.
To prevent polarity inversion, I simply put a little piece of red electric tape on the positive side of the battery pack. You can find red electric tape in any one dollar stores.