Here is what… I love camping – which means that in the summer i find time to go camp somewhere with my friends, usually in the middle of nowhere, get a fire going, grill sausages and play the guitar. But when the night falls, we need light. Full moon cannot be considered as a sufficient light source. Some years ago i made an LED camping light which works still today (and frankly i’m surprised how well it works).
What i want now, is something to spice up this hack. So here is what – I used the MCP1640 boost converter to drain the last electron from the batteries. This chip can work with a ridiculous low voltage and provide enough power to drive a couple LEDs. Which means the 2 AA batteries will operate even longer and the LEDs will be much brighter.
Moreover, rechargeable batteries can be used. Each rechargeable battery provides 1.2 volts. So 2 batteries provide at best 2.4 volts, which is not enough to drive effectively an LED. The MCP1640 chip boosts this voltage to the required levels of an LED, and maintains this voltage (roughly) even when each battery is as low as 0.8 volts, less than half its capacity!
For more detail: High Efficiency Battery Boost Regulator using the MCP1640