/diy/ - Do It Yourself

>>1466943
Well you might be able to get away with RF energy harvesting, if you so desire.

The problem with just having multiple batteries to make the desired voltage is that they have a range of voltages. AA cells for starters come in a variety of different chemistries, ranging from 1.2V to 1.5V, but as they discharge they will get down to 1.1V and 1.3V respectively, meaning the total voltage of 2 cells can vary from 3V to 2.6V. If your load draws higher current every now and then (which it will) than the voltage will drop here also, and a 0.2V drop for 0.5A would not be surprising. Using a supercapacitor to buffer this may help however.

I'd check the voltage ranges on your components to see how generous they are, but chances are they won't like dropping to 2.5V at all. Running it off 3 ~1.5V cells in series with a low-dropout linear regulator would hardly take up much more space, and would last a bit longer. A single lithium ion/polymer cell has a minimum voltage of 3.2V, which is also usable to this end.