[PvK]

A good battle can give as much as +1%, but often it seems to be less than 1%, but greater than 0, and it adds up. Having more than one fleet in a combat either divides the gain, or negates it completely.

Note that if you have a fleet (or ship) with less than the experience to gain a whole point, and then you train that ship up to the max for your training facilities, it will still have it's fractional experience. I.e., a ship with 0.3 experience seems to be trainable up to 20.3 with a facility limted to 20 experience. At least, that's how it seems, by looking at the descriptions, because inexperienced but trained ships and fleets show as "Veteran +20", while those that have seen some action will train up to "Elite +20".

Not that it makes much difference.

PvK