Control module will need a lot of Energizer bunnies to keep it going:
|Component||Work cycle||Current draw|
I’m planning to run it on 8xAA Energizer Ultimate Lithium batteries, wired 4+4 in parallel. Total capacity will be about 6,000mAh at room temperature, reduced to ~2,000-3,000mAh at high altitude, where temperature drops to -40°F.
Lithium batteries are expensive ($2 each) so I did a test with standard alkaline batteries:
Battery voltage dropping to zero means the unit stopped functioning due to low voltage or battery protection.
Burn wire requires a lot of current (1.5-2A @ 3V). It will use a dedicated lithium 123A battery, so that high current draw does not impact control module. I ran ten 5-second burn-wire tests from the same batter, it accommodated all of them with no problems.
Backup radio beacon
I tested Big Red Bee transmitter with standard and high-capacity LiPo batteries. Work cycle was set to 25%: 0.5sec beep — 1.5sec pause — call sign every 5 minutes:
Beacon kept going for 4 days!!! I think I might reduce duty cycle from 25% to 15%-20% to let it run for a whole week.
I will need to test LiPo battery in cold temperatures – I hope it will freeze and loose capacity during ascent, but regain it back as it warms up during descent. So far, I put beacon into freezer and it ran for 4 days – similar to test at room temperature.