This one is becoming more popular and important, as more uninterruptible power supply systems are in demand. These systems provide power to ensure the ongoing operation of critical systems (e.g. those used in hospitals, banks, hotels, etc.). 

Stationary battery systems can pose a number of hazards including fire, explosion, high voltage electricity, electrical and acid burns, and acid contamination. All stationary storage battery systems having an electrolyte capacity of more than 50 gallons (189 L) for flooded lead acid, nickel cadmium (Ni-Cd) and valve-regulated lead acid (VRLA), or 1,000 pounds (454 kg) for lithium-ion and lithium metal polymer, used for facility standby power, emergency power or uninterrupted power supplies, must be under the general supervision of a person holding a B-29 Certificate of Fitness.