battery = peripheral.wrap("left")
reactor = peripheral.wrap("top")
charging = false


while (true) do
  p = battery.getEnergyStored() / battery.getMaxEnergyStored()
  if p <= 0.75 then
    reactor.setActive(true)
    charging = true
  end
  if p >= 0.99 then
    charging = false
    reactor.setActive(false)
  end
  sleep(0.5)
end