Buck Convertor

These little units are so useful for electronic projects, and are really cheap and readily available. I got mine from Communica Electronics in Johannesburg online, and I have a few deployed all over the place. You can use any Lipo/Lithium or lead acid battery as an input source, giving you a variable output voltage, as long as the differnetial is 1.5V (Input). I have a few variants of these things, as some have an LED voltage display if you dont have access to a multimeter or need a small bench supply. This one runs at 3A max current and cost me 24 ZAR.

BMT ADJ DC/DC MODU 3A I/P4,5-40V

Lipo Rider

These are great for powering remote sensors using a solar panel and a battery. I have the older version 1.0 which is a bit outdated. There is a newer version from SeeedStudio.

https://www.seeedstudio.com/Li-po-Rider-p-710.html