any luck
The relay he has cuts out at 4.4v and turns on around 5.8v. The beer was good.

I don't have any easy way to draw the circuit, but we need two resistors (2k, 3k) to make a voltage divider, one of these brown-out reset chips, or something like it:
4.5 Volt brownout reset chip
and a transistor strong enough to drive 250ma to hold the relay on.
Or there's this, for $25: http://www.safetycentral.com/batprot.html
Last edited: