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I am building a PongSat and I need some batteries that can withstand the temperatures found at very high altitudes. The pongsat is planned to go up to around 100 km altitudes where the temperature is around -90 degrees Celsius.

I was planning to use a lithium thionyl chloride (Li-SOCl2) battery since it supposedly can take a beating in terms of low temperature but it is a bit bulky and still doesn't go low enough.

The battery I need has to be as small as possible since it will be housed in a ping-pong ball with the "flight computer" and sensors. It also has to supply 5 volts with at least 25 mA of current.

If anyone knows of anything that could work, please share since I've been trying to get this done for quite a while. I started the project in August 2014 and haven't made much progress because of the battery. More documentation of my project is here: K-Labs PongSat.

Greg d'Eon
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Koppany Horvath
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  • 5V at 25mA is 125mW. That's substantial. Could you use high performance insulation, perhaps in combination with a phase-change material to keep the battery temperature above -55C (for long enough)? – Spehro Pefhany Jun 10 '15 at 22:20
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    How long is it going to be up there? Any reason you can insulate and heat the battery? – Samuel Jun 10 '15 at 22:36
  • People (general public) have already build microsats, are there designs you can use for reference? – pjc50 Jun 14 '15 at 21:47
  • Half the time you will have the Sun for heating. Although all this "keep it warm" talk (as well as your own residual heat) kind of interferes with the idea of measuring temperature. – gbarry Jun 14 '15 at 22:01
  • 4+ years on: 1. Did you do it? If so, how did it work out? 2. My new answer here may be of interest. https://electronics.stackexchange.com/a/467545/3288 The water thermal battery may be of interest - even at such low sizes. Maybe. – Russell McMahon Nov 16 '19 at 12:31
  • @RussellMcMahon I never went through with the project. By the time I would have had the money to invest in the battery, I was no longer interested. All the parts are still sitting in a box just as I left them in 2014. – Koppany Horvath Mar 14 '20 at 21:23

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I agree with the previous answer: Five volts at 25 mA is a lot of power to fit into that small a volume, unless you need it only for a short time. I just grabbed the spec for a standard cylindrical Lithium Ion battery, and see that it has a capacity of 2400 milliAmp-hours, in on order of the total volume you have available. If you had nothing but that volume of battery and a load resistor, you'd get just under 100 hours at 25 mA, though at only the nominal battery voltage rather than 5 Volts.

If you have a short "mission time," where your device sleeps until apogee, then draws 25 mA, you might get away with something like a super capacitor. You'd need a switching supply to convert the (dropping) output voltage to the constant 5V you want.

A better answer approach might be to re-examine your power requirements. Could you use a smaller processor, one that might run directly off a small battery, at much lower current? (You can slow down the clock on many parts to reduce current draw.)

The PongSat page to which you provided a link shows photos of two devices with what look like standard coin cells. While that approach might not produce a design that could go into volume production and reliably work at low temperatures, it might suffice for a one-off unit.

William Watson
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  • The mission time should not exceed two days maximum, but even if it does, most of the significant data will be collected within the first few hours, so a dead battery after 24 hours will not be a problem. Also the processor I'm using is a TinyDuino and I'm not sure if it's possible to change the clock speed on that. – Koppany Horvath Jun 12 '15 at 04:46
  • The TinyDuino seems to use the ATmega328P processor, and is designed to run on small batteries. I found a datasheet on Atmel's web site (tiny URL here: http://tinyurl.com/krefnf8). Amongst other points, it says that active power consumption is only 0.2 mA, that the processor can run on 1.8 to 5.5 Volts, and that it has "Six Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, Standby, and Extended Standby". Two low power modes draw only 0.1 uA or 0.75 uA. What else draws power? Perhaps you could cut that back? Maybe you need to re-examine your assumptions? – William Watson Jun 15 '15 at 20:51
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Apparently, the primary battery in the Philae comet landing module was of the type you proposed (Li-SOCl2). That battery lasted dormant for 9 or 10 years in interplanetary space before it was used during the landing of Philae on a comet. I suspect that you are not being realistic in expecting to operate at -90C. The ambient temp may be -90C, I don't know. But your PongSat will be at an acceptable temperature prior to launch, and will not cool instantly. And, assuming the battery is powering a load, the heat generation inside the PongSat will keep it above ambient temperature.

I would also like to point out that high-altitude air does not transfer heat as well as air at sea-level. The lower the density of the atmosphere, the less relevant air temperature is, and the more important radiation is in determining temperature.

I have not gone through the calculations on required power vs available volume to see whether your requirement are realistic from that perspective. But I think you are imposing unrealistic thermal requirements on your project.

user57037
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