Renogy sells a 10A charge controller (https://www.amazon.com/Renogy-Wanderer-Amp-12V-24V/dp/B07NPDWZJ7 https://www.amazon.com/Renogy-Wanderer-Amp-12V-24V/dp/B07

Renogy sells a 10A charge controller (https://www.amazon.com/Renogy-Wanderer-Amp-12V-24V/dp/B07NPDWZJ7 https://www.amazon.com/Renogy-Wanderer-Amp-12V-24V/dp/B07NPD...) that frequently goes on sale for around $10. It has a RS232 port, and there are libraries for ESP devices and/or ESPHome that can read all of the (modbus) data from the controller. You need a serial adapter or level converter to adapt the serial voltages to 3V and a RJ-12 (6p6c) wire... or you could just buy their bluetooth module that does it for you. Typically used for solar panels, but you could always hook up a 18-20v power supply and let it manage/charge your battery. The nice thing about these controllers is that they can handle multiple battery types and have multi-stage charging algorithms.