2 x AA batteries at 1.2v to 5v 2-3amps via Joule Thief....Is this possible and if so, how?


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How many seconds do you need ?
chunkypies (author)  steveastrouk5 years ago
Firstly, thank you all for the replies! I will only need 5 to 10 seconds at a time. I'm trying to make an ecig with rechargeable batteries. The batteries that I have at my disposal are 1.2v 2000mah. I found this [ http://goo.gl/w0kr4 ] and thought that it might be possible to apply to the same logic to my ecig. Perhaps I'm wrong in thinking that...electronic are not my strong point.
Ecig ? electric cigarette ?
chunkypies (author)  steveastrouk5 years ago
yes, sorry electric cigarette is correct
I can't see the voltage being critical to you. Try two AAs in series and see what happens.

Steve
chunkypies (author)  steveastrouk5 years ago
It kind of works only not very well. Basically an average ecig works with 3.7v to 6v (14500/18650 Li-ion). The ecig i am currently using works on 5v 2a via a USB charger I bought, which is very good but not portable. I'm trying to put 5v into a small box with a push button that I can then carry around with me. And if the batteries run out I could simply buy AAs from the nearest shop and not have to run home to recharge. Does that make any sense?

Also this is the site i found that gave me the idea for AAs instead of 14500 or 18650 batteries. http://puckecig.com/
chunkypies (author) 5 years ago
I've ended up just hooking 4 AA together instead :( not quite as portable but effective. Thank you all for the interest and special thanks to steve!
Don't forget to mark a best answer !

Steve
lemonie5 years ago
Your answer is no.
Not for what you want to do.

L
+1
There is NO way you can pull 5A from an AA battery without the internal connections being stressed to destruction.....
I think he wants to extract the energy into a dc-dc converter, then release it at 5v 3A. I don't think he expects the batteries to be sourcing anything like that. I'm not familiar enough with the converter to know how much it can be made to buffer.
I don't see how you can make that inference, but it still doesn't make this much more viable, and even less efficient.
I don't claim that any such project would be efficient. Nor am I an expert on this by any means.

However, could you not use this circuit: https://www.instructables.com/id/Joule-Thief-Battery-Charger/ to charge a battery that could source 3A? Some low capacity lead-acid?

A 2V 100ma -> 12V 3A -> 5V 3A would be a ridiculous project, but I don't see why it couldn't work.
The Joule thief is the only boost supply people on here generally know about. There are MUCH more efficient designs, when you have 3 V to play with, but you are going to waste 50% or more energy in conversion losses, with your admittedly clever attempt to beat the physics ;-)

Steve
acmefixer5 years ago
5V at 2 to 3 amps is 10 to 15 watts. Someone said "How many seconds do you need?" which may be a little too short, but IF you can get the two AA cells to put out that much (and it's very doubtful you can), then the two AA cells would be discharged in a very short time, a few minutes or less.

On second thought (no pun intended), that just may be a matter of seconds.
quatch5 years ago
A rechargable battery has ~2300 mah capacity, so I suppose the capacity is there. To get that capacity though, you'd have to withdraw it slowly, as the higher the draw, the smaller the total withdrawl.