i had the same issue, but ultimately the problem was that i had grown too reliant on the blue cable
SPOILERS AHEAD FOR ANYONE WHO HASN'T FINISHED THE GAME
the strategy is to first off, try to always have the floodlight on, no matter what you plug it to
- your default behavior should be to make a sweep and then crank the generator
- if the skeleton arrives, do one or two more sweeps and plug the blue cable into the speakers, then plug the spotlight with the pink cable and get cranking
- if lizzie comes down while you have the blue cable on the speakers, use the pink one on the shock cage like normal. by the time you deal with her, the speaker should have finished doing its thing, so put the pink cable into the nav and the blue cable into the spotlight, get some power back and start doing sweeps again
- keep in mind, the nav drains 1 power every 2 seconds, so once you unplug it it's best to keep it unplugged til the last moment