I have a load of used AA/AAA batteries (0.9-1.2V), that I keep to run my LTC-3525 enabled projects like Funky v1 and v2; however the LTC-3525 will work down to 0.8V so the batteries are declared ‘dead’ for a second time after their voltage drops below that level.
I decided to try out such a battery with the LTC3108 energy harvesting board as it can handle inputs as low as 0.1V or 0.02V depending on the build (solar vs TEG) and pump that input up to 3.3V. I used the setup as per the picture below so that the output is available on VOUT2 and it is enabled when voltage reaches the 3.1V threshold. Supercap on the VOUT ensures sufficient pulse load times:
and the physical setup:
.. and a video of it running, as a load I used a LED with a 220ohm resistor:
So as a conclusion, it is an interesting alternative power source to the more expensive TEG/solar cells, plus gives you a satisfaction for sqeezing out all the possible power out of the battery 🙂