I wonder if black holes might be usable as cosmic-scale batteries. Suppose your civ was preparing to settle in for long-term survival into the super distant fut

I wonder if black holes might be usable as cosmic-scale batteries. Suppose your civ was preparing to settle in for long-term survival into the super distant future. You might not need high amounts of energy, just a low constant supply for incredibly long amounts of time. You could drop a good percentage of a galaxy's mass into a black hole, then use the evaporated Hawking radiation over cosmological time scales to power your civ. Suppose that the entities living inside this civ are simulations. A second to us might be tens of thousands of years to them, because their hardware processing runs very slowly because of the low amounts of available energy.