3S Lipo Low voltage cutoff

Other Hardware General Electronics
1

Hey guys

Im doing a project at the moment where i need a lipo low voltage cut off. The lowest the lipo battery can go is around 9V so it needs to cut off at bit above that, I have found this schematic (below) and i was thinking off replacing the mosfet and diode with these (Diode) (Mosfet). Would with work, I'm not sure about the diode.

Thanks Ian

2

This FET has a typical gate threshold of 3volt, +/- 1volt, plus the zener (9.1v) = 11.1-13.1v
That is, if the parts would have perfectly sharp cutoff voltages. They don't.
A zener, loaded with only 100k has a very "soft" kneepoint.
And the FET is a resistor in the Vgs area. it could heat up, depending on the load.
You could try a 5.6/6.2v zener, and replace the 100k resistor for a 10k trimpot.
That way you can adjust the cutoff voltage to ~9volt (for 3 cells).
Leo..

3

Wawa:
This FET has a typical gate threshold of 3volt, +/- 1volt, plus the zener (9.1v) = 11.1-13.1v
That is, if the parts would have perfectly sharp cutoff voltages. They don't.
A zener, loaded with only 100k has a very "soft" kneepoint.
And the FET is a resistor in the Vgs area. it could heat up, depending on the load.
You could try a 5.6/6.2v zener, and replace the 100k resistor for a 10k trimpot.
That way you can adjust the cutoff voltage to ~9volt (for 3 cells).
Leo..

Thanks

do you know of any better ways of doing this?

4

As always when comparing voltages a comparator is the device you need :slight_smile:

5

Make sure you know the difference between a 2S and a 3S battery.

6

michinyon:
Make sure you know the difference between a 2S and a 3S battery.

I only ever use 3S batterys