You could, perhaps, use an SSR, but it would need a drive circuit that detects battery voltage dropping below a threshold and switching off the control LED.

The one I've linked to needs less than 1mA to stay off. However that will cut into battery life. It's a changeover (Form C) type.

Analog switches are possible too, but they usually need some voltage to turn on at all.

All in all, I think a mechanical switch would be your best bet. Quick and easy to flip and generally reliable.

You could, perhaps, use an SSR (Solid State Relay), but it would need a drive circuit that detects battery voltage dropping below a threshold and switching off the control LED.

The one I've linked to needs less than 1mA to stay off. However that will cut into battery life. It's a changeover (Form C) type.

Analog switches are possible too, but they usually need some voltage to turn on at all.

All in all, I think a mechanical switch would be your best bet. Quick and easy to flip and generally reliable.

You could, perhaps, use an SSR, but it would need a drive circuit that detects battery voltage dropping below a threshold and switching off the control LED.

The one I've linked to needs less than 1mA to stay off. It's a changeover (Form C) type.

Analog switches are possible too, but they usually need some voltage to turn on at all.

All in all, I think a mechanical switch would be your best bet. Quick and easy to flip and generally reliable.

You could, perhaps, use an SSR, but it would need a drive circuit that detects battery voltage dropping below a threshold and switching off the control LED.

The one I've linked to needs less than 1mA to stay off. However that will cut into battery life. It's a changeover (Form C) type.

Analog switches are possible too, but they usually need some voltage to turn on at all.

All in all, I think a mechanical switch would be your best bet. Quick and easy to flip and generally reliable.