Maybe your controller is setup slightly wrongly for a current that eventually above the fuse rating.
If true, reduce the current setting.
I am assuming that you have the infos on controller setting up.
Remember, as battery voltage drops, current will increase, so as to get the same amount of power from the battery, that in this case, your bike needs to climb that hill.....
Power = Voltage x Current.
If your battery cables are all thick enough, a slightly stronger fuse would probably "fix" the problems, but I cannot recommend that safety wise!!
I hope this helps.
The (few) controllers that I have seen, they have a setting for the maximum current that may be drawn, this is partly to make sure that the batteries are not "aged" too quickly by supplying too much current.
Finding the Manual can be a problem, maybe someone here has the same controller AND the details you need, assuming that you don't.
It can be as simple as a setting on the LCD display!!
Guessing only, whoever set it up initially, was a bit over optimistic about the ability of the battery to supply a lot of current.
Best guess is reduce the max by 30% first. Then see how that works out for you.
That will also tend to lengthen the lifespan of the battery as well.....
You don't need a fuse because your battery should already have over-current protection in the BMS.
Current in an electric bike isn't very stable, which is why most controllers have big capacitors across the battery wires, so fuses will always have a hard time. They need to be rated much higher than the controller's rating. For a 25 amp BBS02, I'd use a 40A fuse. What's the rating of the ones that keeps blowing?
Sorry vfr400, I didn't see your post. The fuses that blew were 20A. I thought a lower rating amp fuse was the way to go to avoid damage to the controller. I now use a 25A but I take your point and I'll fit some 40A. Thanks for the info.