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I am attempting to design a Low Voltage Cutoff (LVC) circuit to safeguard against overdraining my 12V rechargeable battery. The objective is to halt circuit power once the battery voltage drops below a set threshold, say 10V. However, I'm encountering issues with the following schematic:

Schematic Image

Furthermore, the simulation results at 12V and 9V are as follows:

12V Simulation

9V Simulation

What potential issues might be present in this design, and how can they be addressed to ensure effective battery protection? Why at 9V there is still voltage output?

EDIT 1: Updated schematic. Same issue.

EDIT 2: Tried the circuit linked by @Neil_UK in the comments. I think that I copied correctly. However it is still not disconnected once the voltage falls.

Circuit from another question on the site

12V simulation 2 9V simulation 2

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  • \$\begingroup\$ Q1 shorts the 5 V supply to ground when Q1 turns on. Fix that first. Then figure out how you are going to get sharp relay switching and some hysteresis so that the circuit doesn't oscillate when the battery voltage rises again due to switching off the load. \$\endgroup\$
    – Transistor
    Commented Apr 7 at 17:18
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    \$\begingroup\$ Reposition components on your schematic to minimise kinks, etc. In your case move U2 to the left so that the 5 V rail drops vertically to Q1 collector. A clear schematic will reveal design errors more easily. \$\endgroup\$
    – Transistor
    Commented Apr 7 at 17:20
  • \$\begingroup\$ Rather than re-inventing the wheel, you might want to consider this arrangement and what it has to offer \$\endgroup\$
    – Neil_UK
    Commented Apr 7 at 17:29

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