Hi all,

I am planning a home project, that will be powered by a 3.7V battery.
I was looking around for a 3v cut off circuit for battery protection. I searched this forum, but the many discussions over a thread confused me even more if the circuit works or not.

If you can point me to some diagrams that work, I would appreciate it a lot.


Thanks in advance!

PS: I am a complete noob in this area, have some basic know-how on electronics.

 

By no means is this the only schematic to do it, but simple it is.

 

You want this ----> https://www.ebay.com/itm/173687423956?hash=item287093c3d4:g:r0gAAOSwvVBZeihZ

Or a lithium cell with such circuit disc built-in ----> https://www.orbtronic.com/protected-3400mah-18650-li-ion-battery-panasonic-ncr18650B-orbtronic

----> https://lygte-info.dk/info/battery protection UK.html



There is many flavors and vendors for protected lithium cell

 

What is the maximum load current?

Below is the LTspice simulation of a cutoff circuit using a TLV431 1.24V reference as a comparator:
R4 provides a small amount of hysteresis to avoid chattering of the switch around the set point.
Pot U2 adjusts the set point.

 

By no means is this the only schematic to do it, but simple it is.

That circuit, of course, needs a voltage reference and some resistors to set the trip point at the op amp input.

 

A battery life is shortened when its is discharged below 3.0V to 3.2V.
The datasheet for the very expensive "protected" battery cuts the load at only 2.5V
so the battery needs to be replaced soon and they make more profit.

A battery life is shortened when it is stored at a full charge.
They say to recharge soon so that the battery dies sooner and they make even more profit.

 

What is the maximum load current?

I think max 200 - 250mA -> Arduino and a small water pump(~ 150 mA) and some leds are powered with it.

 

By no means is this the only schematic to do it, but simple it is.

Can you please be more detailed about where these endpoints are coming?
And where is the Output?

 

Here's another option using an Infineon IRF7317 dual complementary MOSFET (a Fairchild/On-semi FD9330L is similar). The circuit is initially off. Pressing the push-button turns it on. The Arduino starts and checks the voltage on A0, if its 1.5v or higher then it sets EN (GPIO3) High, holding the system on, A0 is checked periodically, eg on timer. and if below around 1.25v drops GPIO3 turning it all off.

 

Finally here is arguably the simplest - though it does require soldering of 1.6 x 1.6mm and 2.5 x 2.5mm SMD parts... Provides overvoltage charge, undervoltage discharge, overcurrent charge & discharge protection. Parts cost at Mouser <$2.5 ex p&p