just one battles per turn

[Suicide Junkie]

In the B5 mod, supply restrictions would force most common designs to fight only one battle per month. If that becomes a problem in game, the player can simply mount more reactors on the ship...
Of course, in B5 you would be certaily fighting the second battle with a fleet full of partially damaged ships (no shields, all leaky armor)

In standard SE4, a ship can fight at least 4 typical battles before running out of supplies.
I once had a Dreadnought take on 10 lightly damaged enemy dreads, though, and my ship nearly managed to finish off all of them before running out of supplies. Fortunately, reinforcements arrived in the nick of time, and saved the day!

In an evenly matched battle, however, one side would be long dead before the other ran out of supplies.

Running out of supplies in space is much more dangerous than running out of supplies during a ground campaign on a habitable planet like Earth, so ships carry many more supplies that you would expect a comparable ground force to carry