Battery Pack

Author: Alexander Doknjas

The battery pack is a critical component of the spacecraft. Not only is the battery pack required for continuous operation during the eclipse periods, it is also required to supplement the solar array for peak-power load conditions. Peak power loads such as the radio transmitting, or the deployment mechanisms draw too much power for the solar array to handle, so the battery pack helps out and discharges slightly to prevent the spacecraft from browning out in these situations.

We finally built up a prototype battery pack, and we thought it looked cool, so here are some photos of it. The ORCASat battery pack is unique in that it uses Lithium-Titanate-Oxide cells. While these cells have lower nominal voltage and capacity, they have an order of magnitude lower internal resistance and are able to be charged and discharged down to -30°C without any significant changes in recharge efficiency and capacity (both temporary and permanent). This battery pack can discharge up to 8 A without any issue, and can be fast charged at 6 A. Its total capacity is only ~12 Whr however, but ORCASat is very low power and only requires a battery of ~ 5 Whr, so the trade-off is worth it.

We also wanted to thank our local industry sponsor, JS Foster for manufacturing the battery pack holders, which are the aluminium brackets securing the cells and the electronics together to form the battery pack. These parts are machined right here in Victoria BC, and as you can see from the photos, JS Foster did a fantastic job. Check out their website at https://www.jsfoster.ca/ if you are interested in getting some parts made that look this nice!