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Hello, everyone.
My goal is to achieve a emergency light, capable of running long time, with a decent light, and a small current draw.
I have played, during last years, with Joule thiefs, and recently, I made one with 18650 Li-ion batt, with some modification to last longer, and to give a usable light.
Output of joule thief is charging other 18650 batt, while giving light from two 12 volt / 1 watt led bulb, and each of those bulbs are connected to a pancake coil.
Both batteries was charged when I started the test, and, from time to time, batteries was exchanged from charger to source and viceversa.
A small reminder. Those 12 volt led bulb can`t be fired up by a single 18650 li-ion batt...
Just for fun, I compared the charger with a „simple” Joule thief, similar setup with charger, except no charging second battery.
Also, I`ve tested a „conventional” way of lighting the led bulb, with a step up module.
So, the result are as following:
1. Conventional setup: run time almost 42 hours, initial current draw 40 mA (and 176 mA in the end);
2. Joule Thief classic: run time almost 80 hours, initial current draw 44 mA (and 30 mA in the end);
3. Joule thief charger: still running, 180 hours run time until now, initial current draw 66,3 mA (lowest current draw, until now 47,7 mA)
Setup 1 and 2 was running from a 2900 mA battery, while setup 3 was running from two 3250 mA batt (i was tried to compensate bigger juice from last setup with a bigger curent draw). All Li-ion batteries are new.
Photos and schematics in following posts.
My goal is to achieve a emergency light, capable of running long time, with a decent light, and a small current draw.
I have played, during last years, with Joule thiefs, and recently, I made one with 18650 Li-ion batt, with some modification to last longer, and to give a usable light.
Output of joule thief is charging other 18650 batt, while giving light from two 12 volt / 1 watt led bulb, and each of those bulbs are connected to a pancake coil.
Both batteries was charged when I started the test, and, from time to time, batteries was exchanged from charger to source and viceversa.
A small reminder. Those 12 volt led bulb can`t be fired up by a single 18650 li-ion batt...
Just for fun, I compared the charger with a „simple” Joule thief, similar setup with charger, except no charging second battery.
Also, I`ve tested a „conventional” way of lighting the led bulb, with a step up module.
So, the result are as following:
1. Conventional setup: run time almost 42 hours, initial current draw 40 mA (and 176 mA in the end);
2. Joule Thief classic: run time almost 80 hours, initial current draw 44 mA (and 30 mA in the end);
3. Joule thief charger: still running, 180 hours run time until now, initial current draw 66,3 mA (lowest current draw, until now 47,7 mA)
Setup 1 and 2 was running from a 2900 mA battery, while setup 3 was running from two 3250 mA batt (i was tried to compensate bigger juice from last setup with a bigger curent draw). All Li-ion batteries are new.
Photos and schematics in following posts.
For this setup, I spend almost 15 bucks, so it`s not so expensive. Anyway, think about this experiment at a greater scale: using big batts, and big coils, running a load, and recovering energy by charging a second and maybe a third batt, like in 3BGS setup. I think with an automatic switching between batteries, they wil run much longer. One thing, interesting, about pancake coil: shorting the pancake recovery coil, does not affect too much main coil, like them are isolated somehow! 
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