To unlock Battery in Black Ops 4 Blackout, you need to find the “War Machine”, defeat 2 enemies with it and finish the game. If you fail to complete the character mission for any reason in one match, you need to find the War Machine again in the next game again.
The War Machine mission item can spawn exclusively in the supply drops from planes (Not the supply stashes on the ground)
BEST STRATEGY TO GET SUPPLY DROPS
There are multiple dedicated Helicopter spawn locations on the map (00:23). When the match starts instantly drop to one of these locations and get into a helicopter. Now stay out of the action and wait for the announcer to call out the next supply drop.
If you are lucky and focus on supply drops, you can get 2-3 supply drops each match and have a chance to get the war machine
COMPLETING THE WAR MACHINE MISSION
After you find the War Machine in a supply drop, you have to defeat 2 enemies with it. Keep in mind you only have 6 shots with it and you can’t refill its ammo, so make every shot count. As soon as you down 2 enemies you have completed the War Machine mission and can finish the game