All project data can be found under the following link : https://www.instructables.com/Joule-Thief-Power-Bank/

https://www.instructables.com/Joule-Thief-Power-Bank/

Hundred millions of electric batteries are thrown away each day because their voltage is not enough to be used. Although with lower voltage, these batteries still contain a lot of energy. In this way millions joules remain unused and are forever lost. The idea of the presented in this instructable device is to try to extract as much as possible energy of these batteries and to help in this way keeping our planet alive.

The principle of work of this device called further Joule thief power bank (JTPB) is based on the parallel work of multiple Joule thieves. The reason to use this approach is the following : There a lot of different step up DC/DC converter on the market, but all which I found work with voltages over 0.8V. Some of the Joule thieves (JT) I made was able to work at voltage close to 0.2V. As reference design for the Joule thief I used this site.

My primary idea was to force multiple JT to work in parallel. As beginning I created a PCB supporting 6 JT's.

Their output voltage should be applied to the input of step down 5V converter, which could supply or charge some external device. It also should supply an Arduino used to measure the battery voltage and to display it on some screen. I chose to use small OLED display because of the low consumption. During the design different weak points in the planed approach appeared and solved them in different ways. Keep reading to learn more :-)