Cold weather battery power

Question

I've built a temperature sensor module that runs off of 4xAA batteries and sends data back to a computer via XBee. Works great, until the weather gets cold. At that point, the rechargeable AA batteries (I've tried duracell and eneloop) die very quickly. At 40 or so it seems like they can hardly muster the 3.3V needed to power the wireless.

This needs to be battery powered - running a wire to it isn't an option.

I'm trying plain old alkalines right now, but I was wondering if anyone had any tips on getting enough power out of batteries during the winter. Do I just need to double up and use 8 batteries? Do NiCad or LiPo cells work better than NiMH? Would switching to a different wireless module that can handle lower voltage solve the problem?

Answer 1

Are the batteries actually dead or will they start to work if the temperature is increased? Is the XBee on all the time or does it spend most of its time sleeping?

Assuming the batteries just need to be warmed -- if the XBee does not have to be on all the time you may be able to perform a startup sequence that consists of drawing current from the batteries to warm them up and then enabling the XBee.

A wide input range DC-DC converter would also enable you to startup at lower voltages.

One other note the XBees can be run at 3V. They also draw very low currents in the hibernate modes when run at 3V. I have some plots of duty-cycle and current draw for different operating modes at http://wiblocks.luciani.org/white-papers/intro-to-zigbee.html

Answer 2

Lithium-Ion batteries might be your best option for rechargeables...They have a low self-discharge rate, and apparently work better in cold weather. Unfortunately, all of the popular types of batteries basically stop working at temperatures approaching freezing.

What you might consider doing is putting up a small solar cell for trickle charging, and insulating the batteries. If you can get the insulation right, the trickle charge will warm the batteries during the day, and the insulation will keep them warm at night.

Energizer claims that their Ultimate Lithium works well all the way down to -40ºC

Answer 3

Use something like the Energizer Lithium AA's - they're rated to 40 below zero, and they're not too expensive if you look around. I use them in high altitude balloons where temperatures can get as low as -55 C, and they work a treat for me :)

Answer 4

Lithium thionyl chloride (Li/SOCL2) cells work well at low temperatures and are rated from -55 C. to +125 C.

Here's the datasheet for the Tadiran Extended Temperature TLH Series Batteries.

Here is an article on their application written by Tadiran.

The Cyclon sealed lead acid batteries may be a good choice if you need rechargeable batteries for low temperature. The company name seems to have changed, so I suggest looking up Cyclon at Digi-key.

Answer 5

Try LiFePO4 rechargeable batteries. You can get them in 18650 form-factor on eBay or Aliexpress, there are matching sockets with wires attached for sale, too.

Notice that these cells need lower charging current than typical LiIon - 3.6 — 3.65 volts instead of 4.2 — 4.23 volts.

Cyclists use these in winters for flashlights - even at -20C a fully charged cell can release about 50% of its nominal capacity before voltage drops below critical 2.7V