Battery schemes for cold weather

Other Hardware General Electronics
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I'm planning a low power data logger deployment that needs to run through the winter, including at temperatures potentially dropping to -40 degrees. In normal operation, the system consumes an average of 290 uA, and so can last on AA batteries for 6+ months. My highest current consumptions are during data writes to an uSD card, which will be avoided as much as possible at the lowest temperatures. I'm trying to keep the deployment compact and closed, but space limitations are not too severe.

To help the batteries at the lowest temperatures, I'm thinking about having a super capacitor in parallel. I'm wondering if the following makes sense? The logger system to be powered operates at 3.3V and includes a 3.3V linear regulator (MCP1700).

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The second part of this question is about what batteries to use. One thought is to use D-cell batteries for their extra head-room, even though AAs have enough mAh on paper to do the job. I understand that primary lithium batteries have the best low temperature performance, but that's just from googling, not first hand experience. As best I can tell, nobody makes primary lithium D-cells (just rechargeables, but maybe that's a good option?). So I'm thinking to use "Energizer Ultimate Lithium TM" batteries, but maybe use 6 in combined parallel & series to make up the 4.5 V battery pack I need. Does anyone have experience with these different options (or a suggestion of a better option)?

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Degrees what?

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I was thinking celsius, but I think that 40C and 40F coincide in any case :wink:

1 Like
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  • -40°C = -40°F

  • Have not come across any batteries that are rated to -40.

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Indeed, I'm hoping others have some experience out-of-spec here...and hoping that by not demanding large currents, there will be a practical way...

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are rated to -40 (not kelvin).

and capacity is not even affected at your low discharge rate

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Indeed - should have been clear that the deployment is on Earth, not Hoth.

Ah, thanks for the figure -- where is the figure from?; I must be looking at an abbreviated version of the datasheet.

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Cool-thanks. That makes me think that I've been more worried than necessary - careful choice of the right kind of premium batteries might be the simple answer here.

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According to the datasheet, I wouldn't expect any issues.
And you can keep your circuit more efficient and simple.

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Not Lithium at -40. I doubt any 'small' battery will work, maybe something the size of a car battery with a heater.

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EDIT: Wow, that chemistry is fantastic for -40 as long as draw is kept to 25mA.

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  • I have used these at low temperatures but had problems when temps got below -34°C
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Ah, thanks LarryD, not great news for me, but good to hear first-hand experience -- What kind of peak currents were you drawing when things went wrong around -34?

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  • Definitely not more than 35mA but don’t know what was flowing when things became intermittent. :cold_face:

Edit

  • The batteries were relatively new but maybe a fresh/new battery would work at -40°C .
    When temps got slightly higher, there was no further intermittent operation.

  • Note to self, next time immediately replace battery with a new one . . . :thinking:

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  • Just to fill this out fully, an external AC powered supply was wired in, the intermittent did not return, thus eliminating a circuit problem.