The rules say a LiPo battery must be fitted with a fuse that is rated below the burst discharge rating of the battery (rule 7.8.3 of the current 2018 rules).

So 3.3aH * 150C = 495 amps, which is maddeningly high. Even the constant C is still over 200. TBH, I'd fit something like a 80 amp fuse which is way below the ratings of the battery but I've yet to blow a 80A fuse in either my Featherweight or my Middleweight.