Battery choice for powering 3 servos

[mikami2020]

Hello,

My project is going to be a simply airbrake device for model rocket.
A BMP280 will read the altitude and trigger the three servos to pull open three flaps when it reached a preset altitude threshold.

I read from other posts to learn that I shouldn't power the servos through my Arduino nano and that the servos are operational at 4.8-6V. I also read that a single servo usually draws around 500 to 700 ma when it operates, and only a few ma when it's idled.
I powered it with a 4.8V NiMH 2000mah battery during experiment, and the servos seemed to function just fine. The problem is that the battery is quite heavy for the rocket and I would love to cut weight...

I am exploring options to cut weight and came across a 4.8 NiMH 220mah battery on Amazon during research, which seemed to be much lighter than my 2000mah battery.

Since I only need to supply enough power to the servos to operate for a few seconds and maybe several minutes of standby time before launching it. Three servos will operate at somewhere between 1500-2100 ma, and a 220mah battery should be able to operate the three servos for around 6 mins and idle for hours, which maybe all I need.

I wonder if my assumption is correct and can move forth to get and use the smaller battery.
Any advice or explanation would be appreciate.
Thanks!

[anon57585045]

Rockets are so weight sensitive. Batteries, always heavy. As are three servos. So, why not use a spring operated mechanism instead, as it will only deploy once in flight? You could use a small solenoid or electromagnet latch to release the spring.

[jremington]

Consider a low voltage, lightweight (12 gm) solenoid, like this one: Mini Push-Pull Solenoid - 5V : ID 2776 : $4.95 : Adafruit Industries, Unique & fun DIY electronics and kits

Much smaller ones can be found -- these ones weigh only 1.6 gm

2 Pieces Linear tiny Miniature Solenoid Suction 2x Pull Micro Pneumatic push...

[anon57585045]

You can also reduce the current requirement of the solenoid by driving it from a decent sized capacitor. It will supply the transient current that the solenoid needs, without requiring a huge battery, as would be needed to hold the solenoid in an active position (which you really don't need to do). Just keep the cap charged through a resistor. Caps tend to weigh less than batteries.