3x aa lithium to 5v..?

[Israfil]

I've got my little juicebox now, but now I'm trying to decide what to power it with. It's a 4x AA case, which doesn't seem too big or anything but my understanding of AA size lithiums is they run at about 3.7 volts. I'm running 3 alkaline batteries in it now, and it has been working for me for hours.

The problem is that the batteries I'm using have a rather annoying dropoff over their life. They just slowly fade into nothingness so at about half their full power they drop from the 4.5v total to around 2.25v, which is well below what I would consider enjoyable.

I'm quite handy at building things physically, and can wire circuits together, but I don't fully understand electricity's nuances. (read math fail) I need to find a way to take 3 lipo batteries down to around 5 volts to really hit that sweet spot and have great battery life. I'd like to use AA lithiums because due to their size I'd assume their life beats AAA. Any solutions would be greatly appreciated.

 

[UberDuper]

My suggestion, if you're happy with a 4xAA box, would be to use 2 or 3 14500 in parallel along with a TI PTN04050C to boost the 3.7v to 5v. I've built one but the 4xAA box is too bulky and it vapes much hotter then any other 5v mod I've used. I've tested, it's def running a solid 4.9v under load. I've considered building a 3xAA box that has selectable 3.7 (whatever the batteries are at), 5v and 6v using that setup.

UD.

 

[Israfil]

Sounds like a good plan....would that part and running parallel increase explosion chance though? Also, good luck on the selectable sounds like a fun trick. I may add switches to run 1 2 or 3 batteries at some point, but for now I like the idea of tasty little box that can vape for forever on a full charge.

 

[Israfil]

Ack...I looked at that beasty...they've got free samples but looking at the pictures of it I have no idea how to use it. Maybe one of these would work? +5V Fixed-Voltage Regulator 7805 - RadioShack.com

 

[UberDuper]

would that part and running parallel increase explosion chance though?

I'm going to go ahead and say yes. But only because of the increased potential for user error. Putting one battery in backwards and one in correctly would be the same as taking two in series and shorting them. That's about the worst case scenario for these batteries.
Here's the box I built. Nevermind the poor soldering and the illogical position of the switch in the circuit. I relocated the battery terminals to put positive down on both batteries. I've heard that these batteries are designed to vent towards the positive side but that's probably pure myth and I haven't done anything to confirm it. I also did it that way cause I thought I'd be less likely to install one backwards in that configuration.

Using batteries in parallel and a booster, there'd be no need for switches to add or remove batteries. My 5v unit can run with a single 14500 battery in the box, albeit with significant voltage dropoff.

UD.

 

[Israfil]

Hmm...well its coming, ordered the samples from Ti, gotta love free. Only trick will be figuring out how to use that thing... It has 4 posts apparently and I have no clue what I'd be soldering to where.

 

[UberDuper]

Negative (ground) to pin 1. Vin to pin 2. Vout to pin 3. I think those are the right pin numbers. Pin 4 isn't used in a 5v configuration.

UD.

 

[Israfil]

hmm...the good news looks to be that i can run nimh or nicd batteries if i get that to cut costs until ive got enough money for the lipo batteries.

 

[Israfil]

wait.....so i do the positive from the batteries to pin 2, and the pin 3 to my atomizer? hmm...gonna make wiring this thing a little more interesting but i think i can manage it thanks man. Now all i gotta do is wait for it to arrive.

 

[UberDuper]

nimh and nicd are like 1.2v, no? I don't think the TI booster can run on less then 3v input.

UD.

 

[Israfil]

with 3 of em i'd be running 3.6volts I like the 3 battery setup, solved my NIMH problem. The real trick is gonna be the wiring. I don't want to rewire it too much, I wonder if I could place it on the negative side of the atomizer for the same effect....probably not yah?

Edit:3.6volts in serial

 

[UberDuper]

I don't know what the max current or capacity is on AA size nimh or nicad. It might not be ideal for the booster. Also you would need to rewire the box into parallel when switching to 3.7v lipo or lion. I'm pretty sure the booster would not regulate 11v down to 5.. not that 3 14500s in series could deliver 5 amps..

UD.

 

[Israfil]

No no, sorry. I wasnt clear. I can rewire the box easily enough to parallel for the lipos by swapping the orientation of 2 of the battery leads and avoid resoldering the connections. All i have to do are separate a positive and negative lead and swap em, then run a wire to the other positives, and one to the negatives (which I can do easily enough without solder) The problem is that the positive wire is very short as the atomizer is right near the positive wire of the serial configuration I'm using now. Getting the wires to connect properly to the atomizer was a nightmare due to its small size and the large size of the tip of my soldering gun. Just wondering if it'd still work the same if i put it on the negative wire side, or if I'd have to swap the polarity (positive black wire? lol).