+77 power generation, turrets connected, turrets not able to sustain themselves. I'd like to see or know why this is like this, or what "power generation" actually means.
The more power surplus you have - the faster turrets will charge. In your case, it sounds like +77 isn't enough. Also, remember you can store extra power in capacitors between waves.
The capacitors seem to provide instant power recharge for your turrets, basically just an extension of the turrets own battery charge. You can't rely on your power generators to get you through a wave, need to have the power stored up ahead of time.