Amateur hour: How do I shut off a path if the supply goes under n volts?

Hello, all. First post. I searched the forum but didn't find an answer.

I'm trying to build a battery meter for a single cell Li-Ion Mintyboost. I was going to use the **broken link removed** but I'm afraid the required source voltage is too high to run from an almost-dead 2.9v, and I didn't really want that many LEDs in the array. What I'd like to do is create a circuit that I can have 5 or so LEDs, with the top one shutting off under 4v, the next at 3.8, the next at 3.6, etc. I'm very, very inexperienced with circuit design (but trying to learn) and would appreciate any help anyone wants to give me. Also, feel free to correct any incorrect or confusing nomenclature I've used.

Thanks!

The LM3914 is probably your best bet. It should work down to 2.9 volts if you choose the Vf of the leds to be under that by a few tenths. You can adjust the dividers to use 4 or 5 leds and leave the rest unused. The alternative is a couple of comparators a voltage reference and all the resistors that come nicely packaged in the LM3914.
If you would rather build one we can do that as well.

It is a bad idea to use LEDs as a Li-Ion battery voltage indicator because the continuous fairly high current of the LEDs (and LM3914 IC) will quickly make the battery dead and might kill the battery.

Instead you should use a very low power comparator to blink an LED when the battery is fairly low and disconnect everything when the battery voltage is 3.0V per cell.

RonV: I'll pick one up and give 'er a try then.

AG: Thanks for the warning, but I was just planning on hooking it to a momentary switch.

I use Li-Po batteries in my electric RC airplanes now but when I used Li-Ion cells robbed from a laptop the voltage slowly dropped as they were used until it reached about 3.2V when the controller turned off the main motor. After a rest of a couple of minutes (maybe cooling the cells) the voltage was back up and I flew the battery a few more flights before charging.
So your idea of measuring the battery voltage might not be accurate.