Hi all, can anyone recommend a circuit to me. I have a 20 volt lithium battery I want to disconnect when it drops to 16 volts I'm new to this stuff and am keen to learn. I don't want Hi-tech, I know I should be monitoring each sell. but its not needed in this application. Your help will be very appreciated.

Regards Harry

 

What current are you taking on this battery, you can use a mosfet transistor and Tl431 zener or window comparator op amp?

With the circuit shown, make
R2 5.6K,
R3 1K,

this will give you a cutoff of 16.5V.

 

Here's an LTspice simulation of Dd's slightly modified circuit:
I added R1 to provide about 100mV of switch hysteresis to minimize oscillations around the switch point.
Also used a value of 5k instead of 10k for R4 to sharpen the switching action.

The circuit shuts the output off at a nominal 15.95V.
If you want to be able to adjust that voltage, you can change R2 to a 10k trimpot

The MOSFET can be any P-MOSFET with the appropriate voltage and on-resistance rating.

How much load current do you expect?