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I've been checking the forum and Google but still haven't got precise solution to my current question. In short, we are looking for rechargable batteries for Arduino that survive under -40 Celcius degrees.

Our group is going to deploy several sensors in the Polar Region, Arctic, to study the permafrost.

These sensors are dispersed in the area around a community, within some kilometers. The data collected by the sensors are to be saved with Arduino-based nodes, and then uploaded to cloud for quasi real time.

Hence, the Arduino modules serve as dataloggers and LoRa nodes. In the community, we've got power line to power up the LoRa bridge. But all the end nodes out of community cannot access AC power source.

Lacking a source of power, the end nodes rely on batteries and solar panels.

There are several considerations here.

For example, sensing and LoRa transmission need to be set to very low frequency, like, once per 15 minutes, to reduce the power consumption. We would set it via programming, and set Arduino to sleeping mode for the rest of the time.

Here comes the question I'm having trouble with:

What kind of battery and solar panel should we use? The temperature on site is very low, going to -40 celsius degrees in deep winter.

Most commonly used battery types cannot survive these temperatures. We also need the battery to be rechargable, which could be charged with solar panel (of course, mostly during Spring to Fall while there is sunshine.)

Our technician used lead acid batteries in the past but the performance was marginal.

The batteries on some sites were severely damaged and even broken during winter. And solar panel and power source regulator? We plan to shorten the operating time so we can reduce the size and cost of solar cells, but still, we need them to stay alive.

Any suggestions?

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    \$\begingroup\$ Why wouldn't you just use the same kinds of power systems that are already in use in that region? Surely you're not the first to face these requirements. \$\endgroup\$ – Dave Tweed May 18 '19 at 13:33
  • \$\begingroup\$ I wonder if you couldn't make a solution out of the problem. Thermoelectric generators operate on temperature differences. If you've got -40 degrees at the surface, you can dig down below the frost line and get zero degrees. That's 40 degrees of temperature difference. I don't know the frost depth where you are, or the efficiency of thermoelectric generators at those temperatures. Or how hard it'd be to dig a deep enough hole. \$\endgroup\$ – JRE May 18 '19 at 16:23
  • \$\begingroup\$ Or just dig a deep hole and keep your batteries down at the bottom (well insulated and water proofed.) Deeper is better. \$\endgroup\$ – JRE May 18 '19 at 16:24
  • \$\begingroup\$ Why rechargeable? What is your expected lifetime? How often must it report in? A primary battery might be cheaper overall, and spend your effort reducing the power consumption of the sensor. I've made gadgets with a regular Arduino mini that last 6 months on a little 9 V battery, but there are things that last a year or two on a CR2032, like a heart rate strap. And you can have a pack of D-cells. \$\endgroup\$ – tomnexus May 19 '19 at 6:13
  • \$\begingroup\$ A quick check on google returned a number of results which one you choose depends on the detailed spec for the battery which you need to develop. \$\endgroup\$ – RoyC May 19 '19 at 12:43
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Some Lithium primary cells are rated for military temperature range (down to -55°C). Check out the Israeli company Tadiran.

Maybe you can combine the primary cells with rechargeable cells to extend the life, just ensure that the storage temperature of the rechargeable cells includes your lower limits.

You could also consider insulating the battery and using some of the battery power to keep the battery itself warm enough. This could cause problems with overheating during charging conceivably but maybe slow charging is acceptable since more hours of light are available when the temperatures begin to rise. This also works for LCD displays that need to work in extreme cold (film heater attached to the back of the display). There might be a fix with a damper and/or ducted fan too.

The ultimate solution is an RTG, but that's probably impractical for you.

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I suggest that you reconsider using rechargeable batteries. Instead, use something like Energizer Ultimate Lithium batteries (not rechargeable) which operate down to -40 and up to 60C.

My thinking is that you will have many months of time you need to operate without solar power anyway. So you will need a big battery. How much smaller can the pack be if you use rechargeable and add solar? Is the solar really going to improve your system design?

Here is a link to the battery technical data sheet: http://data.energizer.com/pdfs/l91.pdf

Here is an excerpt from that data sheet showing the relationship between temperature and capacity: Temperature Effects on Capacity

At the very minimum, you should calculate how many of these cells you would need for your project without solar, and decide if it is reasonable, rather than rejecting it without consideration of the details.

It will be difficult to have something work reliably, unattended in that environment. I think eliminating solar will be a big win for system reliability, if it is possible.

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Many years ago (47) we used carbon batteries in a couple of Navy sensors I worked on. We were able to recharge them, but I don't know how efficient they were.

When Alkaline batteries became available we tried them and found they freeze and burst at -17 F. The carbon batteries worked no matter how cold the sensors got.

Just a thought...

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  • \$\begingroup\$ How low in temperature were the carbon batteries able to go in your application? \$\endgroup\$ – mkeith May 19 '19 at 17:52
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    \$\begingroup\$ As I recall, the coldest the sensors reported was -52 F. I don't remember how low the carbon batteries were rated... \$\endgroup\$ – Wendall May 20 '19 at 0:08

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