I am designing a small network deployment for several buildings without temperature regulation. In planning the power, I can find very little about acceptable UPS batteries for these conditions. Lead acid batteries won't handle the year-to-year temperature changes (potentially -10°F to 115°F [-23°C to 46°C] indoor at site), and I have found very little about alternatives that would be appropriate to provide for "turnkey" UPS solutions like a 2U rack-mount UPS (12V F1/F2 terminal).

It seems like there are a lot of batteries out there that do work in temperature extremes, but they haven't really reached the UPS market. There are some Lithium Ion and some Lithium Iron Phosphate batteries that claim to work with existing UPSs.

If I drop either of these types in a standard UPS (1, [2]) that is not quite rated for the temperature (most are rated for 22°F to 110°F [-6°C to 43°C] ), would this be safe and last a few years?

I also haven't found much discussion on these kind of scenarios, at least from a networking perspective. Is there any obvious information I am missing?


I settled on including two thermostat switched 50W heaters in the cabinet, about 5 inches below the UPS. It is ventilated, but I think these should keep the batteries above freezing. Leaving this question open, as I don't think this is really an answer to my overall question.

  • \$\begingroup\$ Are you sure you have the degF correct? seems well within the automotive environment where SLAs are in wide use. \$\endgroup\$
    – kenny
    Commented Jun 4, 2014 at 1:12
  • \$\begingroup\$ They may work well for starter batteries, but for SLA UPS batteries (which I guess count as deep discharge), I have read that the lifetime is seriously shortened by heat and have some other complications in cold weather. \$\endgroup\$ Commented Jun 4, 2014 at 1:51
  • 2
    \$\begingroup\$ @metatheorem -10°F [-23°C] indoor doesn't sound right. Did you mean outdoor ? \$\endgroup\$ Commented Jun 4, 2014 at 2:10
  • \$\begingroup\$ How much power do you need to deliver, for how long? (KW hrs?) Are you locked in to using batteries? How about a fly wheel based UPS? Bit more expensive, different lifespan concerns, and more energy efficient. I haven't seen any that are small enough to be rack mountable, (but I haven't looked too hard) \$\endgroup\$ Commented Jun 4, 2014 at 2:15
  • \$\begingroup\$ @NickAlexeev No, these are unheated buildings; basically really big sheds. \$\endgroup\$ Commented Jun 4, 2014 at 11:22

3 Answers 3


The new Lithium batteries can withstand high temperatures and variations, compared to standard vrla batteries. The upfront capex is 3 times though.Li-Ion TCO


I have had cause to revisit this problem for a new project, and have learned quite a bit more about batteries to understand this problem. There is lots of information out there; marine and solar power are applications where battery use (and charging) at varied temperatures are common.

I still think the EE exchange site was the best location for this, though it may be relevant to folks on Server Fault, Network Engineering, and Robotics as well.


  • Know your energy needs before planning.
  • All batteries work best near room temperature.
  • Batteries can be used at widely different temperatures but unattended batteries should always have some amount of temperature regulation, and should be checked on and tested regularly. If you live somewhere unusually hot or cold, take extra precautions in regulating temperature.
  • Use lead acid batteries for UPSs.
  • Find a UPS or charge controller that charges based on temperature if possible. This will extend battery life.
  • Allow batteries to vent.
  • Heated battery mats are a good idea for cold.
  • Read the battery spec sheet before buying.

For my application last year (that caused this question to be opened), a standard rack-mount UPS worked out well (temperature range of 0°F to 95°F) as a backup battery. It has some heaters beneath it. Its batteries may last another year or two but probably not more. We only needed about 300W for minimal 5 - 10 minutes of backup for this.

Some accumulated knowledge that anyone in IT working with batteries outside of the data closet should know:

First, batteries have three different conditions where temperature matters: on the shelf (when stored unused), during charging, and during discharging. Shelf storage temperature is not really a concern for this problem, as batteries are always online.

Batteries can typically be discharged at a wider range of temperatures than they can be charged. For stationary applications though this means we have to ignore the discharge temperature and find a battery whose charge temperature range is wider than the environment temperature range.

Example temperature ranges taken from a Power Sonic gel battery are:

Charge: -4°F (-20°C) to 122°F (50°C)

Discharge: -40°F (-40°C) to 140°F (60°C)

This is pretty good, but: at colder temperatures battery voltage drops a bit and discharge capacity drops a lot; in higher temperatures the overal lifetime of a battery drops the longer it is exposed to higher temperatures. Around 68°F/20°C is considered ideal for lead acid batteries.

Charge rate also matters for temperature, and most of the UPSs (UPSes?) we use in IT do not offer any control over this; charge rate is how many amps are pushed back into the battery. Lower charge rates are safer for high temps and do not wear down the batteries as much.

Specialty outdoor UPSs exist but as a market does not have the range of products that data center UPSs do. Alpha Technologies has some good stuff but they are not plug and play (you will need an electrician); I mention them as they have a great web site with all information available, including specs and manuals.

user43325 is right that lithium batteries also have similar tolerance for high temperatures as lead batteries, and longer life. But they perform poorer in very cold (freezing) temperatures are also more expensive out of the gate. Most lithium batteries are also more prone to thermal runaway than lead batteries (google "laptop fire"). Development of lithium batteries may make it a reasonable choice for UPSs in the future, but I would not put any in a server room today. Budgets are too small, the risks too high. Here is some good info on lithium use in UPS applications


It takes very little energy to keep the batteries warm in a well-insulated container. Can you use the waste heat from whatever you are backing up?

  • \$\begingroup\$ Just backing up an 8-port switch and a power brick. I'm uncertain how I could measure the temperature increase this would provide. \$\endgroup\$ Commented Nov 21, 2014 at 3:49
  • \$\begingroup\$ You can't make well insulated container if temperature at summer is high. Unless you open it after winter. \$\endgroup\$
    – Kamil
    Commented Dec 21, 2014 at 16:09

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