I’ve got an opportunity to potentially loft a small camera module on a high altitude balloon launch next month. I had written some very simple code for an ESP32-CAM module which can be had for about $7 direct from China, or 2 for $10 from Amazon with Prime. The other day I decided to see how long I could expect the battery to last. I grabbed four fresh Alkalines from the Dollar Tree, and measured the voltage for the 4 pack as 6.45V.

I then did something really dumb: I hooked the voltage up to VCC and GND on the module. I should have checked the schematic. The appropriate way to hook it to 5V and GND. Net result, one module no longer responds. I might be able to repair it. Stay tuned for that.

But I then put it on the dashboard of my car and let it sit for the entire workday. After recording something like 1450 images (about 8 hours) the battery voltage had dropped to 5.784V (or about 1.44V per cell) which suggested that they actually had no problem at all. This suggests to me that we probably don’t really need to go to any kind of exotic cell: even at low temperatures, even cheap alkalines will have enough oomph to power the thing for the 4 hours or so that we estimate will fly. I haven’t done the math comparing their relative weights which is another metric we might use in evaluating them.

But in any case, here’s the video, mostly just showing clouds zipping by for about eight hours.

A few other things I learned:

The camera has a fairly narrow field of view. Similar modules are available with fisheye lenses: I ordered one via Amazon, as well as a couple more ESP32-CAM modules to replace the one I killed. I also learned that the AA battery holders I have do not really secure the batteries very well. In the real launch, I should wrap some tape around the modules to keep the batteries from dislodging in flight.

I’m also not sure that the auto-exposure stuff is working entirely correctly. I’ll have to read the datasheet for the camera module a little bit more carefully.

More work in progress.