I was thinking what else could I use this Joule Thief kit for? It dawned on me that I could harvest energy from a homemade battery. So this morning I set out to make a zinc copper vinegar battery. I took a piece of copper pipe and a zinc coated bolt from my junk pile. Cleaned the copper pipe with a sanding sponge. Placed the two pieces in a plastic container, poured in some vinegar, connected to the JT_kit001b and wow it worked!! There was light coming from the LED!!! I measured the voltage coming from the homemade battery at ~550mV and the battery current was somewhere around 15mA.
Next I thought, well I could remove the LED and put a rectifier diode on the output of the Joule Thief board to see what kind of voltage I was getting. I put a 220uF capacitor on the rectified output and it charged up to >10VDC in a few seconds.
Well onto the next experiment, trying to recharge a depleted AA NiMh battery with the Joule Thief harvesting energy from the zinc copper battery. Will update with results at a later date as I think this may take a couple of days. Here is the Joule Thief schematic showing what I was doing.
Joule Thief Circuit Battery Charger
Update: 6:40AM Oct 31st : Last night I started with completely depleted NiMh (520mV with 10mA load) After charging overnight the static value is sitting at 1.210V. The Zn Cu battery is not fairing so well the output voltage is sitting at 425mV and the output current is now at a paltry 2.9mA (the JT circuit is still running, LED is still lit) The bucket of vinegar is looking really ugly. I think I may have to find a more robust source of Zn or another material to make the ‘battery’ out of.
Update: 9:20AM Oct 31st after running the JT charger circuit on the Zn Cu battery for about 12 hours the input voltage dropped too low (about 390mV) to keep the circuit running. The NiMH static voltage is at 1.225V. Time to try a different input battery.
Another experiment will be trying to harvest the low voltage output from a thermal electric cooler (TEC, Peltier device or Peltier cooler) when heating one side and cooling the other.