It has been noted by battery experts that Lithium batteries can be frozen hard, at low temperatures, and recover their usefulness when thawed. This might be useful for GLXP systems planned to stay on the Moon “Overnight”. The temperature on the Moon falls quickly at sundown to about -173C = 100K (about the normal temperature of LOX and a little warmer than Liquid Nitrogen at Earth normal conditions). It stays in that range for nearly 14 days, then warms up quickly.

In order to survive such freezing, the Lithium batteries need to be in a “partially charged” state – Not Completely Discharged. Completely discharged Lithium batteries will be destroyed by freezing. Also any attempt to draw power from very cold or frozen batteries will destroy them, and make them unusable when thawed. To survive, the batteries must be charged to a planned state, and then totally isolated from all electrical loads before the rapid sunset cooling.

Several types of “Supercapacitors” including those based on Aerogel should work very well at cryogenic temperatures, although their energy storage capacity is quite limited. Solar cells normally work very well cold, even to cryogenic temperatures, if mounted so they are not destroyed by thermal stresses. Of course, there will only be Earth Shine to generate power before sunup, but this is about 100 times brighter than Moon Shine. The solar cells will not need to warm up to produce power once the sun hits them.

Electronic systems vary with cold. Micropower electronics usually sees its miniscule electrical operating currents drop much lower as cryogenic temperatures reduce leakage. Reduced clock speeds make this power reduction even more pronounced. Field effect transistors, including MOS FETS and CMOS circuits usually work even better at cryogenic temperatures, while the older “Bipolar” Transistors often stop working. Some resistors change resistance radically, while many metallic film resistors change only moderately. Normally temperature stable capacitors often don't change much with extreme cold, while liquid electrolytics freeze and become useless.

One practical technique is to place a “control core” system, with its batteries, in a Thermos Bottle. This will can reduce the cooling to a level the battery power can balance for the 14 days. Alternatively, a variety of liquids can be used to release heat as they freeze and keep the temperature in the “Bottle” from falling further. This energy density can exceed that of practical batteries.

One last, exotic option, is a form of “Nuclear Battery”. The low energy Beta radiation provided from Tritium can either be used to generate power directly, impinging on a modified form of Solar Cells, or used to produce light from a phosphor screen (as used in modern “Radium Dial” - Glow in the Dark – replacements) and that light converted by normal solar cells. This can be sufficient to keep a micropower controller in operation and even recharge the Supercapacitors for brief radio reports.

All of these problems become more severe at the interesting Lunar South Pole, “Where the Sun Don't Shine”, and temperatures are close to 40 degrees K, much colder than liquid Nitrogen for years on end.

If the “Standard” Lunar scenarios aren't challenging enough or you are tempted by the extra prize money, then dig into these little problems and a few suggested solutions.