Well I thought they had!
I’m hoping to use my Kodak Zx1 camcorder to video the entire journey from launch to (crash?) landing. Running on normal alkaline cells it only manages 45 minutes before switching off, which isn’t nearly enough for the flight. Besides, alkaline cells are poor at the low temperatures the payload will face, so instead everyone uses Lithium cells of one sort or another.
I intended to use Energizer AA Lithium cells, as these are intended to be a direct replacement for AA alkaline cells. So as a test I put 2 in the Kodak camcorder and switched on to see how long they would last. I was expecting 2 hours+. I got about 2 seconds! The battery symbol flashed up a warning and the thing switched itself off!
Now, Lithiums start at about 1.7V so my assumption is that the device has an over-voltage check in the software and it’s trying to protect itself. I’ve emailed Kodak to ask what the voltage limit is, but I’m not expecting a useful reply. So this weekend I’ll try a couple of options:
- Put a Schottky diode in series to drop the voltage a bit. This option would then make it easy to put extra Lithium cells in parallel (adding a diode for each pair) to get a longer run time. My calculation is that 2 AAs will be a bit marginal so 4 AAs will be fine.
- Put 4 AAs in series (so delivering up to 6.8V) then putting this through and low-voltage-drop regulator and then into the 5V power socket on the size of the camcorder.
I need to measure currents and running times with both, and then decide on the best option (one that will give me the longest running time).