Recommended · for some experience
How to Make a Battery Protection Circuit (over-discharge protection)
Why people recommend it
DIY Perks builds an over-discharge cut-off for lithium cells using a low-voltage alarm module to trigger a relay; used as the starting point for home-made protection boards.
Watch for: relies on a battery alarm buzzer module
In their words
This video on a battery protection circuit is the basis for my cutoff part, I would just need something like the voltage alarm to activate the relay.
Texas-72 on electronics.stackexchange.com, Jun 2023. CC BY-SA.
I can see from this video that it is not a big deal to build one, however, I don't have a battery alarm buzzer.
Physther on electronics.stackexchange.com, Sept 2017. CC BY-SA.
Here is a link to the video, it may help you:
JosephFTaylor on electronics.stackexchange.com, Jul 2015. CC BY-SA.
