Squeezing the last electron from AAs

[jdurand]

That definitely works. A couple of other variations:


1) fully charged battery pack voltage is less than the total voltage needed...use a step-up switcher that will keep on going until the batteries are sucked out.

2) battery pack starts over the voltage needed and ends below. This is very common with lithium batteries...4.2V charging, about 3V discharged and you need 3.3V out. There are switching regulators that automatically change from step-down to pass-through to step-up to cover the range.

If you plan to recharge the batteries, NiCd shouldn't drop below 1V per cell. With lithium it's around 3V, check the battery specs.

When you pull batteries to really dead quickly they will get hot. Also may leak. So watch your application.