Special Polar Equipment

Rechargeable batteries are used for summer-only and year-round polar seismic experiments. For summer-only experiments, due to the roughly continuous sunlight, stations can be powered solely with rechargeable batteries.

For EPIC Polar experiments the preferred rechargeable battery is an AGM (Absorbent Glass Mat) battery manufactured by Concorde Battery Corporation. Both the Sun Xtender PVX-420T and PVX-560T work well for a summer deployment where only a limited amount of storage is required for cloudy days.

Primary batteries are usually not necessary for summer only deployment due to the ample amount of sunlight available.

EPIC's Polar Group specifically designed a power management module to control the charging and manage the power system in extreme-cold temperature environments. There are two main parts in the power box:  The solar charge controller and the power switcher.  The solar charge controller, as the name implies, takes care of the proper and efficient charging of the batteries when solar energy is available.  The power switcher takes care of switching from the rechargeable batteries to the primary batteries when the rechargeable batteries' voltage dips below a threshold, and switches from the primary batteries to the rechargeable batteries when the rechargeable batteries' voltage gets high enough from solar charging.  Both the charge controller and the power switcher were tested successfully for operation at -55C after having been subjected to -70C for several hours.

The Cold-rated Guralp CMG-3T seismometer is described in detail in the Polar section article "Sensors for Year Round Polar Programs".

Rechargeable batteries are used for projects using solar and/or wind charging systems. EPIC's Polar Group has used SunXtender AGM batteries by Concord succesfully for many deployments. These batteries, aside from being reliable, offer several advantages. They are sealed and non-spillable, which makes then safer and easier to handle in the field; they have a low self discharge rate, which is important for a low power system, with extended periods of time between charges (arctic conditions); and they are exempt of DOT HazMat requirements (49 CFR Section 173.159) provided that they are shipped in their original package or in a package that satisfies the requirements of 49 CFR 173.159(d).

Most electronic equipment and batteries used for seismic stations become unreliable at temperatures below -45C.  For this reason, it is very challenging to make year around seismic studies in the Arctic and especially the Antarctic, where winter temperature can dip below -80C. On the East Antarctica Plateau, ambient temperatures a couple of feet below the snow surface are between -50C and -60C.