lm431 - Circuitos electrónicos
The high power "zener diode" circuit presented here can be used for obtaining a highly accurate, temperature and voltage stabilized outputs from high current sources, safely. The low power zener diodes that we normally use in electronic circuits are specified to work with low currents, and therefore cannot be used for shunting or stabilizing high current supplies. Although higher rated zener diodes are available, these could be relatively expensive. Nonetheless, it is actually possible to make a.......
http://www.homemade-circuits.com/2016/02/high-power-zener-diode-circuit.html
https://jopewiring.blogspot.com/2013/03/making-simple-smart-automatic-battery.html
http://dangerousprototypes.com/blog/2012/03/12/digitally-adjustable-precision-reference-driven-via-pwm
https://felicinwiring.blogspot.com/2013/07/flat-battery-indicator.html