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.
Best Answer
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.