Why Lead Acid Batteries
Lead Acid batteries are used in UPS applications. This is primarily because of cost. Newer technologies such Lithium-ion are not considered generally due to their high cost (approx.3x). Li-ion and other technologies under development for renewable energy application may become viable at some point, but not in the near future.
Lead Acid Technology – VRLA AGM Lead Acid Batteries.
The most common battery deployed for UPSs’ are sealed, valve regulated lead acid (VRLA) AGM (absorbed glass mat) batteries. VRLA batteries are basically a very high quality car battery. We recommend deploying 10 year design life batteries. 10 year design life means, if kept at the correct temperature and constant trickle charge of 13.6 -13.8V, and used in a standby mode only, the battery will have a life of 10 years. However, if they are discharged significantly even for a few cycles, their “design” life is reduced dramatically. This is because the active chemical coating the battery plates (lead sulphate) actually erodes off the plates during discharge. This erosion becomes severe when the battery is discharged deeply.
Factors affecting battery life. - Temperature
Lead Acid batteries are very susceptible to temperature. VRLA Batteries should be kept at an ambient temperature of 25 degrees C. Every 2 degrees C above 25deg C ambient can reduce the battery life by approx. 1 – 1.5 years. We recommend that the UPS’s ambient temperature is closely monitored using a suitable IoT Monitoring Portal.
Depth of Discharge
The charge and discharge cycle of a battery reduces battery life dramatically – and is very dependent on the depth of discharge (DoD). A car batteries for instance are relatively reliable for a 3-5 years plus, as their DoD normally less than 1 or 2 %. And then immediately charged again as you drive off. However, in Southern Africa where extended power outages are common, the depth of discharge of the UPS battery can go as deep as 80 to 100%. For this reason it is highly recommended that UPSs be monitored by an IoT Monitoring Portal. This monitoring system should monitor the UPS’s DoD and advise operators to stop the discharge at maximum 60 – 70% DoD,
Expected Battery Life
Typically the battery manufacturer’s a, return to factory, 1 year warranty which covers manufacturing defects only. In the South African load shedding environment, UPSs’ using a 10 year design life battery can expect the useful life for batteries should comfortably reach 5-7 years. This pre-supposes a 7×24 IoT Monitoring service, regular on-site servicing and an air-conditioned environment.
Install the highest quality 10 year design life, sealed, VRLA batteries in a cool air-conditioned environment. Insist on regular servicing and consider using an IoT based Monitoring Portal. If these conditions can be achieved you should be able insist on at least a 3 or 5 year on-site battery warranty from your supplier.