They definitely need to be safe for indoor use so they can't vent, they should probably support deep cycling due to the nature of backup power supplies, and I imagine they should have relatively long life under near maximum charge to be ready.

Do most manufacturers use some flavor of AGM batteries? Any NiFe due to the robust, long life? Are they customized in any way that makes them different from a typical deep cycle AGM you'd buy at the hardware store?

I'm interesting in building my own (non-solar, just grid-tied) indoor backup power supply and I imagine whatever batteries are used by UPS manufactures would best since our requirements match almost exactly.

  • \$\begingroup\$ Domestic use UPS designs typically use lead-acid sealed batteries. A quick search for technical specifications of products from APC and other UPS manufacturers will confirm this. \$\endgroup\$ Commented Apr 5, 2013 at 11:43
  • \$\begingroup\$ Actually, you are wrong. UPS batteries are not Deep Cycling. They are meant to be on full charge most of their lives, and when the power goes out, the ups circuit cuts off external sourcing when the batteries get to a reasonable low, not a deep discharge. It's cheaper that way. \$\endgroup\$
    – Passerby
    Commented Apr 5, 2013 at 11:50
  • \$\begingroup\$ NiFe is probably not used because they off-gas a lot of (flammable) hydrogen and oxygen gas when charging, so they have special storage conditions and you need to water them. That wouldn't work for most residential UPS owners \$\endgroup\$ Commented May 18 at 2:49

2 Answers 2


Lead-acid is still very common. Higher end and newer devices seem to be using lithium ferrophosphate (LiFePO4).

For building your own, lead-acid is probably the most accessible and also one of the easiest to manage electrically.

  • \$\begingroup\$ I'd expect a UPS to use AGM or Gel versions of lead-acid batteries, although sealed (maintenance-resistant) liquid electrolyte types may also be used. \$\endgroup\$ Commented Apr 5, 2013 at 17:32

I think NiFe is not used because it lasts too long. A manufacturer wants to earn money, so it does not make sense to use a battery that never needs to be changed.

e.g. Jay Leno bought a Baker electric car that was in a backyard for over 80 years with dead batteries: http://www.classicandperformancecar.com/features/columnists/292504/jay_leno_hotrods_a_100yearold_detroit_electric.html

batteries are dead, flat tyre.

Later he said that he replaced the acid and now he is able to use them indefinitely: http://www.popularmechanics.com/cars/jay-leno/vintage/4215940

My Baker still has some original alkaline batteries. These have lead plates and use acid; we wash them out and refill them regularly and I'll use them indefinitely.

But is is strange that he was talking about an acid. Baker electrics sold this car with Edisons NiFe batteries:


One was sold to Thomas Edison as his first car.[1] Edison also designed the nickel-iron batteries used in some Baker electrics. These batteries have extremely long lives with some still in use today.

NiFe batteries are working with electrolyte: http://en.wikipedia.org/wiki/Nickel%E2%80%93iron_battery

The nickel–iron battery (NiFe battery) is a rechargeable battery having nickel(III) oxide-hydroxide positive plates and iron negative plates, with an electrolyte of potassium hydroxide.


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