ExU2 Generator Manager

local side = "back"
local battery = "xu2:tilepowerbattery_0"
local function energy(x) return peripheral.call(x, "getEnergyStored") / peripheral.call(x, "getEnergyCapacity") end
while true do
    rs.setOutput(side, energy(side) < 0.9 or energy(battery) < 0.3)
    sleep(3)
end