Perhaps you need a UPS to keep them running?
Are you able to find out what power they use?
(they should have a plate on them saying the power usage - watts etc).
This would keep them running when the mains power goes off, if your power use is low then they may be able to run for a few hours with a UPS.
(UPS = uninterruptible power source/supply)
Uninterruptible power supply - Wikipedia, the free encyclopedia
ups : Maplin Electronics