It doesn't.
Example with diodes:
EDIT:
So in this case if the main power generators fail, the two tiers of batteries that come first will still feed energy to the critical grid part until they die.
And tier 3 will never supply energy back to the less important systems, keeping it's own availability up to the very end or till the problem is fixed.
You could even imagine multiple of such tiered "trees" and limit failures of more generic sections to their direct sub-sections while not sacrificing supplemental effects during normal operation.
A beautiful cascaded energy network.
Example with diodes:
Code Select
PWR Gens -> generic consumer
-> batteries tier 1 -> diode -> more important consumer
-> batteries tier 2 -> diode -> critical important consumers
-> batteries tier 3
EDIT:
So in this case if the main power generators fail, the two tiers of batteries that come first will still feed energy to the critical grid part until they die.
And tier 3 will never supply energy back to the less important systems, keeping it's own availability up to the very end or till the problem is fixed.
You could even imagine multiple of such tiered "trees" and limit failures of more generic sections to their direct sub-sections while not sacrificing supplemental effects during normal operation.
A beautiful cascaded energy network.