Design of a single cell low voltage reverse battery protection circuit
Seems like a lot of hassle for just a reverse battery protection.

An alternative solution I can think of:







simulate this circuit &ndash; Schematic created using CircuitLab

If the battery is reversed, a lot of current flows through the diode. Many circuits (chips) can handle such a small reverse voltage but do check that. The large current blows the fuse. For an evel lower diode voltage drop, use a Schottky diode but beware that these leak reverse current at higher temperatures.

You could make the fuse a standard replaceable glass fuse or a polyfuse (these recover after some time).

Yes another solution is a mechanical solution. I once worked on a product running on a single AAA cell. It had a non-electronic reverse battery protection. The positive battery contact was recessed slightly into the plastic case. Therefore the flat negative terminal of a battery cannot make contact with it. But the positive battery pole protrudes a little bit, just enough to make contact. Have a look in some devices (like a remote control) which work on AA or AAA cells and you'll see what I mean.