Given how much torch you can power off one of these, I'm not clear why you'd need two of them for a badge, since any conceivable use for that much current is going to start heating up the badge PCB fairly quickly. They're usually sized for >1A each, and you can get >10A off them for short periods, which is very lively for a badge pinned to flammable clothing.
Assuming decent cells with low ESR (say, <30mOhm), one such cell will deliver hundreds of amps when shorted, making things a little bit more lively than your estimation. :)
(A few hundred amps isn't a lot for a shorted battery, but these are tiny cells so that's what you'll get.)
Two cells was probably selected for one of: Voltage to avoid boost converters, capacity to avoid having to do extensive power optimization to make it run the whole event, balance to make it hang even off your neck.
> Two cells was probably selected for one of: Voltage to avoid boost converters, capacity to avoid having to do extensive power optimization to make it run the whole event, balance to make it hang even off your neck.
It's likely not voltage because they're connected in parallel.
Quite oversized amounts of power for 2 ESP32s running, last I measured a ESP32 board I have running it would consume some 120-180mA.
That is highly dependent on the exact ESP32 model and current power state. They can use in excess of 500mA with peaks of 800mA, and can easily use >250mA constant at 3.3V. Some draw much more than that.
A board with a few bits and bobs on and a single 18650 cell might only last, say, 8 hours on a charge.
Now, a well optimized board with a low-power ESP32 and proper use of sleep states would make that number go from 8 hours to over a week, but that does take a lot of extra effort and may not be worth it over just slapping on another cell.
2 ESPs and a 4” color LCD screen (and a keyboard).
Depending on how bright the backlight was, that could eat through battery. And if they were using the wifi for any active communication, that increases power too.
I suspect they wanted it to last the entire weekend with the display always on. The original design probably only had one cell (maybe even smaller battery with built-in protection) and they hurriedly switched to two 18650 cells at the last moment.
They probably went with parallel because that seemed easier, no need to switch to another voltage regulator and charge controller.