Project to send a balloon into lower space with payload
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Joined: Mon 12 Oct 12 2009 9:17 pm


Postby Rris » Thu 09 Dec 09 2010 11:48 am

We need to test batteries which we might want to use onboard.

I think at this point the options we have for batteries are:
A123 cells
Standard LiPo cells (Flightmax for eg)
Newer LiPo cells (Turnigy Nanotech)
NiMH cells
Li-ion cells (like phone batteries)

I require 13013mW of power including the regulator loss, assuming a 3.5hr max time required that's 45547mWh.

Using a 6s LiPo (2.7v nominal) that would be 2811mAh, so a 3000mAh 6S battery would supply the maximum current draw i can provide (including the HD camera, and comms transmitter running at full power 100% tx time). This will be between 450-500G with a LiPo.

Not powering the camera, and going to a 50% comm transmit time (as in the datasheet) will pull this down to 1663mAh required. A 2200mAh 6S lipo is about 350G. The camera runs for 2.5hrs with it's own battery. Powering the camera for 1hr would being the draw up to 2217mAh over the 3.5hr period.

Tests to run on batteries (room temp battery placed in -30C):
* Battery temperature curve at 10,000mW of draw (can it self heat at all?)
* Battery capacity at 10,000mW draw (how much is lost to the cold)
* Voltage curve at 10,000mW draw
* Battery resistance when chilled to it's self heated temperature - including wiring.
* How long the battery can supply 10,000mW of power for before reaching minimum voltage.

Posts: 8
Joined: Thu 02 Dec 02 2010 3:05 pm

Re: Batteries

Postby chris1seto » Wed 15 Dec 15 2010 1:15 pm

Are you also going to test how the battery performs in a vacuum?

Better safe than sorry.

Daniel Wee
Site Admin
Posts: 2052
Joined: Wed 25 Feb 25 2009 8:00 pm

Re: Batteries

Postby Daniel Wee » Wed 15 Dec 15 2010 2:52 pm

By putting it in a vacuum. Those are not hard to create in lab conditions. In all the cases reported thus far, none have mentioned any problems with batteries failing due to the low external pressure though.


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