I'm playing a lot with solar powered systems using ultracaps for energy storage. I'm also powering some small ~3.3V systems directly from LiFePO4 cells, charged by solar power.
In both cases I'd like to be able to power on the load when the ultracaps / battery reaches a specified voltage V(on), keep it on until the voltage falls below a second voltage V(off), and then keep it off until it rises back to V(on). V(on) > V(off)
Ideally, the circuit to achieve this should be as simple as possible (fewest components), cheap and all components readily available. It must also not draw much power itself (max. a couple of mA).
So what would people recommend? I've searched online and found microcontroller based solutions, but this seems like overkill and simple Schmitt triggers, but these don't quite fit the bill either - at least the simple implementation I tried never worked reliably.