Servos for HAB

[Oandu]

Hi,
we have the problem that we want to use servos on our balloon, but we didn't find servos for temperatures up to -70°C jet. We have already tested the AM Racing 1151 Digital Servo which is waterproof and has a metall gear and one of those standart cheap 9g servos. Both failed at temperatures under -50°C. Both of them also moved slower at lower temperatures. We tested both servos with and without lubricants, (without seemed to work slightly better) but all of our tests failed.
Do you have any experiences with servos or other motors at those temperatures and could help us?
Thanks a lot in advance!

[David Johnson]

Hi

At high altitudes (often below −40 °C):

• Chemical reactions inside batteries slow down
• Internal resistance increases
• Voltage under load drops more quickly

This means:

• The servo may receive lower voltage than expected
• It may move slower, stall, or jitter
• Battery capacity can drop dramatically (sometimes to 20–50% of normal

Dave

Sent from my iPhone

On 6 Apr 2026, at 21:06, Oandu <oan...@gmail.com> wrote:

Hi,

we have the problem that we want to use servos on our balloon, but we didn't find servos for temperatures up to -70°C jet. We have already tested the AM Racing 1151 Digital Servo which is waterproof and has a metall gear and one of those standart cheap 9g servos. Both failed at temperatures under -50°C. Both of them also moved slower at lower temperatures. We tested both servos with and without lubricants, (without seemed to work slightly better) but all of our tests failed.
Do you have any experiences with servos or other motors at those temperatures and could help us?
Thanks a lot in advance!

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[Nick McCloud]

On Monday, 6 April 2026 at 21:06:54 UTC+1 Oandu wrote:

Hi,
we have the problem that we want to use servos on our balloon,

Both failed at temperatures under -50°C. Both of them also moved slower at lower temperatures. We tested both servos with and without lubricants, (without seemed to work slightly better) but all of our tests failed.

Where are these servos located - inside, outside but vaguely covered or just strapped to the box?

The time a payload is at -35, I rarely see -50, is quite short and if there is some thermal mass &/or insulation, the servos may never get that cold. But I'd certainly strip them down to re-lube them with something suitable for cold weather. So sticking them in the freezer for an hour isn't a realistic test. You can download temperature data from Grafana on SondeHub to see what you are likely to encounter in your region.

Alternatives may be something like a solenoid.

As for the batteries, hopefully they are inside a polystyrene payload box as it's game over if they go out of temperature spec - even Lithium batteries have their limits!