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Can I mix old and new batteries in a Smart-UPS?


Can I mix old and new batteries in a Smart-UPS?

Product Line:

Smart-UPS, Smart-UPS Online


All models, All Serial Numbers


Many Smart-UPS have either multiple internal battery cartridges and/or the ability to add external batteries. 


No, you should not mix old and new batteries within the same Smart-UPS system.

As VRLA (Valve Regulated Lead Acid) batteries age, their capacity is reduced. Your Smart-UPS batteries are connected in parallel and all batteries are charged at the same rate. Mixing batteries of different ages can result in some batteries being under charged while others are over charged, which would lead to reduced runtime. 
  • When replacing the batteries in a Smart-UPS system, you should replace all battery modules (internal and external) at the same time.
  • When adding additional external battery packs to a Smart-UPS system, you should first replace the existing batteries (internal and external) if they are more than 1 year old.
  • You should not mix batteries with more than a 1 year age difference in a single installation.
  • For detailed information on how to replace battery modules or add additional external battery packs, refer to respective user manuals

For more information on VRLA batteries, please see APC White Paper #39:
Battery Technology for Data Centers and Networking Rooms: VRLA Reliability and Safety
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