load factor vs battery life

[Anonymous user]

Hello,

We use Smart UPS 750 units and experience 10 - 14 month battery life.  I assume this relates to our high load: 3.2 Amps at 220V. Is there a chart or documentation available documenting load vs battery-life-expectancy?

My thanks in advance,

Bruce

[BillP]

Hi,

Please review Schneider Electric FAQ FA158934 "What is the expected life of my APC UPS battery?"

We do not have a chart based on load and usage. We do have runtime and efficiency charts available at http://www.apc.com/shop/ro/en/products/APC-Smart-UPS-750VA-LCD-230V/P-SMT750I

 As the FAQ lists there are many causes of battery degradation. If the load is greater than 80% and the UPS runs on battery often the battery will need to be replace sooner than the expected life. 

[MarkC_apc]

The Schneider "FAQs" are a good source of information.  However, for SLA batteries (in my experience) being used in most UPSs, one of the additional factors not mentioned is the "drying out" of the very small amount of electrolyte in the battery.  The  pop-valve arrangement is, by necessity very cheap and subject to production tolerances that could lead to early loss of electrolyte - especially in services where high power levels are required for "backup" at frequent occasions.  IMHO, it is time that really "smart" charging techniques be built into these "smart" UPSs that allows for 95% SOC limits to minimize "boil off" - especially if Lead acid is going to continue to be pushed for these critical systems!  As UPSs move to good BMS (battery management systems) that are absolutely required by the lithium based battery systems, this will be the needed results of long battery life and many cycles available even when "stressed to the limits" of the systems.  Just my honest opinion.

[MarkC_apc · Accepted solution]

BTW, these APC "smart" UPSs are already so smart, programming in really good BMS should not be much of a problem!