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