really surprised no one one said mekanism mod
this is my battery reservoir for my entire base about 125 ultimate energy cubes
I supply it with power from a Big reactor that is set for low power output, basicly it trickle charges the batteries but when i need a burst of power like when a quarry is running, that needs power and then as the ore is ender chested home it is automated into my mek triple ore processing system that for about 8 hours needs lots of power to run non stop. and my batteries will hold for it, that resover will drop to half power storage but by then quarry is done and the big reactor is trickle charging my batteries again back to full power
Note: these batteries are also portable, you can break them and they retain there power