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Dead Battery circuits.

gary350

Well-Known Member
I pulled about 15 used D batteries out of the trash can to do some experiments and learned I can more than double the life my 1.5 v batteries and use them all the way down to 0 volts.

2 LED flasher circuit needs 2 D batteries in series = 3.3v when voltage gets below 2.8v this circuit stops working. This circuit will run 1 year on 2 new D batteries.

1 LED flasher needs 3 D batteries in series = 4.8v when voltage drops below 3.3v it stops working. This circuit 3 new batteries last about 7 months. This would be a better circuit if it did not use more power power than the 2 LED circuit & only needed 2 batteries.

Joule Thief circuit will run on 1 new D battery 4 months with no LDR circuit and 8 months with the LDR circuit. With no LDR circuit stops working at .9v. With LDR circuit stops at 1v.

I started using 3 used batteries in series to run the 2 LED flasher & 1 used battery on the Joule thief. As voltage drops lower & lower when LED flasher stops working I add 1 more battery in series the circuit runs for several more months. I keep adding more batteries in series the flashers keep running several more months.

If joule thief runs on 1v why won't the other circuits run on 1v too they use the same transistors & LEDs ?

I have been using only the 2 LED circuit then throwing batteries in the trash when total voltage dropped below 2.8v but now I am reusing all the old batteries until they are all 0v.

It was very helpful to put variable resistors in the LDR circuit so I can fine tune when the LEDs come on according to how dark it is when sun goes down. Also when batteries get too low to work I can turn the variable resistor ohms down to make the circuit work again & get more life out of the same batteries.

Red LED is 2.1v and Blue LED is 3.4v I can probably make joule thief battery last a tiny bit longer by lowering the output voltage then use a Red LED..

I also learned if the discharge capacitor is smaller than 100uf LED flash is not bright enough to be seen 200 ft away outside after dark.

Joule thief R2 50K variable resistor is turned down very low in the 400 ohms range with a AA 1v battery it works good & blue LED is bright. I need to change 50K to something smaller maybe 1K and change to Red LED..

It is a bit funny, I sure am getting my moneys worth from these batteries I wish I still had the $50 worth of used batteries I threw away a year ago.

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audioguru

Well-Known Member
Most Helpful Member
The 30 turns inductor in the Joule Thief boosts the voltage each time the transistor turns off. Most solar garden lights use a similar circuit to light its 3.3V LED when the 1.2V rechargeable battery cell voltage drops to 0.9V, but they "blink" the LED at a high frequency so it looks like it is always lighted. The high frequency uses a tiny inductor.

I modified most of my solar garden lights by adding a rectifier diode and filter capacitor so that the pulsing boosted voltage drives a colors-changing LED.
 

gophert

Well-Known Member
Most Helpful Member
The 30 turns inductor in the Joule Thief boosts the voltage each time the transistor turns off. Most solar garden lights use a similar circuit to light its 3.3V LED when the 1.2V rechargeable battery cell voltage drops to 0.9V, but they "blink" the LED at a high frequency so it looks like it is always lighted. The high frequency uses a tiny inductor.

I modified most of my solar garden lights by adding a rectifier diode and filter capacitor so that the pulsing boosted voltage drives a colors-changing LED.
So, if I drive through Canada some day and see a house flashing in technicolor, can I assume it is yours?
 

Visitor

Well-Known Member
I used to sell those ......
People paid money for those? ;) I only got the give-away ones, designed to sell batteries. The original ones (at least) were awful. You had to stuff it full of coins to keep the batteries making contact.
 

picbits

Well-Known Member
They were rarely sold, you used to get a flyer through with an offer on the outside for a free one (or the beach balls / frisbee etc) - you did occasionally have the odd person who actually purchased one .......
 

audioguru

Well-Known Member
Most Helpful Member
So, if I drive through Canada some day and see a house flashing in technicolor, can I assume it is yours?
I have a box full of my outdoors solar garden lights that are in the garden in spring, summer and fall. I have 33 of them in the window and on the table in my computer room. My city has a new bylaw that says flashing lights are not allowed but so far nobody complained about mine.
 

gary350

Well-Known Member
I guess one of these would be a gold mine.... or maybe a nice holder for 5 dead batteries!

View attachment 129234

You could put several used batteries in your flashlight, build a joule thief circuit, replace the old bulb with LEDs, you would have a good flash light.

This is my 50 year old antique flashlight. Those old slider switches made terrible connection the light was always flashing on/off and sometime they would go off then you had to shake them or turn switch on/off several times to make it work again. I got tired the bad connected so I soldered a wire to the metal body that holds the light bulb, soldered a wire to the battery contact in the bottom end of the flashlight case, connected both wires to a house light switch, it worked excellent for 40 years and still works good.

I bought several good LED flashlights none of them last long, switches go bad and LEDs stop working. I have 14 LED flashlights that don't work even the expensive ones stopped working.

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gophert

Well-Known Member
Most Helpful Member
We are ending the hack-of-the-month contest early. We have a winner!

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MacIntoshCZ

Active Member
...... but it says 15A 120V AC only - how is it going to work properly on a DC torch ? :p
It has build-in pwm regulation. 60Hz
 

audioguru

Well-Known Member
Most Helpful Member
High current switches do not work well in low voltage, low current circuits because their contacts usually have silver plating that quickly corrodes. The silver turns black (silver oxide) and needs a high voltage high current spark to make it conduct electricity. Many times I purchased switches at an electronic parts distributor like Digikey for low voltage, low current switches and IC sockets having gold plating that NEVER corrodes. They cost the same and are smaller than the switches with thick silver plating.
 

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