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Update on Homemade Zinc Copper Battery Experiment

Update on Homemade Zinc Copper Battery Experiment

Here is an update on the Joule Thief Kit experiment, where I was trying to charge a NiMh battery using a homemade single cell Copper Zinc battery. See this post from October

The first experiment using a zinc plated bolt failed as the zinc plating came off of the bolt in about one day. So I set off to make a much better zinc plate. I found a certain unnamed Copper coin made after a certain date was greater than 97 percent Zinc. Zinc has very low melting point of 787.15 degrees Fahrenheit. I have a wood burning stove that makes for a nice melting furnace. I took about 50 coins and stuck them into a tin soup can and inserted them into the fire and after about 10 minutes I had a nice molten Zinc soup. ( I do not recommend doing this because it is dangerous )

I carefully removed the soup from the fire and poured it slowly (to prevent the copper chunks from coming out of the bottom of the can) onto a large #10 sauce can that was inverted. I let it cool for a long while before removing the zinc slug from the can.

I put this battery together using a plastic peanut butter jar, a 3/4inch x 8 inch Copper pipe and the zinc slug. added some water, salt, and vinegar. I connected the Joule Thief Kit with clip leads to the Copper and Zinc. Took the output from the Joule Thief Kit and rectified it with a 1N4001 diode and put that into a completely depleted NiMh battery ( I use a white LED in series to indicate if the circuit is operating). This is the same schematic circuit from the late October post. This battery charger has been running since November 1st and the NiMh battery Voltage is up to 1.237V. Since I am not exceeding the 1/40th current rating this battery will not overcharge.

The only maintenance I have been doing is adding a little vinegar every time the liquid level drops from evaporation (that is about 1/16th cup a week), I will post another update when I find time.

I suspect that I can charge 4 NiMh batteries in series with this circuit, and that might be a future experiment.

I know many of you think how can this be useful since it takes a month to charge the NiMh battery, but there are many situations where I think this could come in handy. This low cost circuit provides a source of light as well as being a battery charger. There are plenty of places in the world where electric power is not a luxury of life, and there are plenty of things that you can make low voltage sources with that the Joule Thief circuit will happily run off of. This is what energy harvesting is all about, lets make some use out of something that we could not use before.

Joule Thief Copper Zinc Battery Low Voltage Energy Harvesting Experiment

Joule Thief Copper Zinc Battery Low Voltage Energy Harvesting Experiment

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.