Just in case you're an idiot like me, this needs to be in COOP fleet battles.
I've just done about 10 in solo and of course that doesn't count. There can be population issues so i'd suggest doing this when the US is on so at least you can find some people to do it with. Searching for Easy and Any Team will speed up your search.
If your team is very bad/feeding, i'd suggest taking the support ship with targeting beacons and Rocket turrets. On offence take out enemy fighters and AI units until the shield drops on a cap ship, then spam your turrets and stay alive. They'll do most of the work and if you aren't dying you won't be losing morale as fast. On defence you just focus the raider once its shield is down and farm AI ships, that's the fastest way to get it to turn.
This build works in ranked too by the way, in my experience. Helped get me to valiant.