[lstodd]

3.3V, that's pretty standard nowadays.

I don't have a breakdown, it was cobbled together from whatever was around, an STM32 devboard, some regulators, some half-dead li-fe-pos, almost useless BMS from ali, this sort of stuff. Obviously that ate significantly less than an RPi, but I can't say how much, don't actually remember since that wasn't the problem.

Another take was a weather station, basically an ESP on a ~2500mAh 18650 li-ion.

That lived for like a week on a charge, stuff being fetched from it every minute over wifi.

I would recommend against using NiMH for that, just get some 18650s and work them between 80-40% charge, they'll last forever.