Solar panels that power a rotary converter to act as a day time charger for batteries.

[deathincarnate]

This would make the bases silent in the day time too. except for the electric motor for the rotary converter but you could then use a single beat truck in the whole map with a dead pimp you have to go through to get it and he could be severely mutated with a cut scene showing how he ate an infected bear and that is how he got his huge size. this would be like a mission given by the traders for stalking and hunting. like a holy grail mission. ( The last one. The big one.)
 

by the way a fun pimp beat truck would have four beat alternators. that is four silent motor cycles. don't you would need a hydraulic motor and that could be found inside a mine shaft or forklift or then different ones like the big scoop machine.