making adaptor for RC 7.4v-11.1v lipos to work 5v regulated usb

[Youssefa]

Hi All,

I Wanted to use/recycle my RC lipos for my usb EGO VV. I have several high discharge 20-30amp batteries that have seen better days. And while they no longer have enough power to sustain a Brushless motor, I figure that they have sufficient life left stepping down, to power 3.3 - 4.19v Ego.. The trick is I am not that knowledgeable in this area. I may be able to assemble the components, but don't know enough bout electric stuff to conceptualize it.

Basically one end will be female USB port then a step down regulator then a RC type lipo plug....


What parts do I need.... Oh and some sort of housing like a gutted flash drive.

 

[Youssefa]

I am not sure about fine soldering... I do mostly large battery connectors and wire to wire. I was looking for something that I kae a "portable PT" with for like when I am sitting on the couch and near a PC.... I have a GG and a Saber touch on the way, but those are for mainly going out and about. I have a few 5000mah and 2200 mah 2 cells that I used on a first person flying rig. they drain fairly quick when trying to keep a 2 lb plane in the air at 25 amp draw. I figured that a 2 amp drain from atty would be perfectly fine. I saw this, but cannot find in stock. It has a nice big dial on it and display... I am not confident that I would be able to solder up a unit like this/

Tenergy DC-DC Voltage Regulator (Adjustable DC-Buck), New! | Battery Superstore

 

[jimbalny]

From what I've read, Lithium Polymer batteries are pretty volatile. If they've seen better days and no longer reach a full charge then I'd just go ahead and recycle them.

 

[CraigHB]

The hobby LiPos are actually no more volatile than the ICO (LiCo) batts. The difference is the application where they're typcially used runs them on the edge, that is, powering high performance model aircraft and cars. I've read about cells bursting into flames upon a hard crash or during a fast charge. Also, they're typically used without any protection so any screw-up on the user's part or electrical failure on the model's part may be rewarded with a flaming battery. That's probably why they get such a bad rap.

If you incorporate the normal over-current and over-charge protection into a Lithium Polymer hobby battery, they are no more hazardous than any of the other protected Li-Ion batteries out there.

To address the OP's question, you can use a buck (step-down) switching regulator with a 2S hobby LiPo. You'll want something like the Murata OKR-T/6 or OKR-T/3, Dimension Engineering DE-SWADJ3, or Texas Instruments PTR08060W. I think all of the buck regulators have short circuit protection, but I would add a PTC fuse as a backup. Never can be too safe with something you'll be putting up to your face. There's lots of posts in this forum on how to wire up those regulators. Just do a search on the parts I've mentioned.

For convenience, I would mount the charging connector accessible in the mod so you don't have to remove the cell to charge it. Of course, take all the precautions you normally do when charging your hobby LiPos.

As far as using old batteries, I imagine they're pretty worn so you might be dissapointed with the run time you'll get out of them. Also, they're probably 3S or 4S and you need 2S. Since you already have the balancing charger, it would be worth it to buy a couple new ones or at least use ones that aren't too worn. The 2S LiPos are really cheap from HobbyKing. Even the least expensive 20C ones would be way more drain than you'd ever need for an e-cig mod.

With reliable short circuit protection and by charging in a safe area (which you are already used to doing as an RC hobbyist), they wont' be any more hazardous than than 18650s most people use in their mods. That's not to say they will be perfectly safe. All Li-Ion cells present some risk to the user, even the ones in your cell phone and laptop computer. BTW, cell phone batts are typically Lithium Polymer with little difference to the RC LiPos in terms of internal construction, other than a greatly lower maximum drain.

 

[Youssefa]

.......................

 

[jrm850]

Yousefa, Castle makes a programmable BEC that you could use without having to do any fine soldering.

BEC 10A 5.1v Programmable Castle Creations: SlickZERO Hobby Products

You may even want to pull the cover off of an existing BEC to see if you can adjust the output. Look for a trimmer pot on the board.

edit: whoops, only goes down to 4.8v

 

[BuzzKilla]

Yousefa, Castle makes a programmable BEC that you could use without having to do any fine soldering.

BEC 10A 5.1v Programmable Castle Creations: SlickZERO Hobby Products

You may even want to pull the cover off of an existing BEC to see if you can adjust the output. Look for a trimmer pot on the board.

edit: whoops, only goes down to 4.8v

LOL that was the first thing i thought of....

but when i read your post, i had to sit back and think of how low of a voltage it would drop to. and the two that i have are PC programmable only, no pot adjustment from the Castle Creations B.E.C.

the best part is, as long as your under 25V this sucker can regulate to the O.P.'s desired 5V. i don't know about its efficiency though.
even though this unit is tiny, i still don't see me wanting to hook this up my RC packs and vaping off of it... would look too funny...

make a 10ohm atty and crank the B.E.C. to 9V for some crazy plumes of vapor.... i think i may try that out on my spare... lol

i think that would be a good solution for a table top mod with a car battery.... OK ill stop now.

 

[BuzzKilla]

From what I've read, Lithium Polymer batteries are pretty volatile. If they've seen better days and no longer reach a full charge then I'd just go ahead and recycle them.

RC packs are volatile if miss treated... and that can be said about any Lithium type battery. so no need to fear, the vaping community doesn't put nearly the amount of stress on these batteries like the RC community does.

i've driven my RC car into barriers and curbs at 50+mph(for 3 years), and my 5000mAh 11.1V Li-Po pack hasn't blown up yet... but i've been schooled on the tell-tale signs of a pack that is on its last leg....

 

[BuzzKilla]

they're typically used without any protection so any screw-up on the user's part or electrical failure on the model's part may be rewarded with a flaming battery.

this is not entirely true. they are unprotected, but the ESC's(electronic speed controller) that the li-po's are attached to have battery monitoring built in to the programming. too keep you from over-discharging, or reversing the polarity, among other things.

the only time i've seen an RC pack fail, is when charged after it has been damaged... more common on RC fliers due to the occasional bad landings, or in a violent crash with the touring cars.

a "puffed (swollen)" pack is a dead give away that a pack should be retired. if a cell gets punctured after use, only an incompetent hobbiest would try to charge it...

aside from that, i keep charging my packs at a 1C charge rate, and they will last for a really long time.

i've gotten my 2900mAh 18650 fully charged from 3.3V in under an hour on my hobby charger... the wall chargers that everyone praises on these forums doesn't even come close to it... and my charger has more redundant safety features than i care to list...

 

[jrm850]

lol, you would look like you are in a hospital bed with some IVs and and ekg hooked up with all those wires. Heck, why stop there... get one of those servo pulse controlled H-Bridges hooked into your reciever and vape remote control with a DX-7 in the lap.

LOL that was the first thing i thought of....

but when i read your post, i had to sit back and think of how low of a voltage it would drop to. and the two that i have are PC programmable only, no pot adjustment from the Castle Creations B.E.C.

the best part is, as long as your under 25V this sucker can regulate to the O.P.'s desired 5V. i don't know about its efficiency though.
even though this unit is tiny, i still don't see me wanting to hook this up my RC packs and vaping off of it... would look too funny...

make a 10ohm atty and crank the B.E.C. to 9V for some crazy plumes of vapor.... i think i may try that out on my spare... lol

i think that would be a good solution for a table top mod with a car battery.... OK ill stop now.

 

[BuzzKilla]

lol, you would look like you are in a hospital bed with some IVs and and ekg hooked up with all those wires. Heck, why stop there... get one of those servo pulse controlled H-Bridges hooked into your reciever and vape remote control with a DX-7 in the lap.

i deal with on-road RC's, so no DX7. i think i can get my DX3-R to control a table top PV to blow vaper in my general direction.
throtle trigger to regulate air flow, steering wheel to control direction, & 3rd chanel switch to activate the atty



but back on topic...

the O.P. wanted to connect all this to the guts of a ego VV???

IF, and this is a big if, you feel comfortable and have the tools. You could take apart your cell packs, solder them together in parallel, keeping everything at 3.7V. this way you could take advantage of the battery capacity and just make a box mod with the guts of the eGo VV.

this combination would give you a few thousand mAh of battery life, with adjustable voltage... but it would be a HUGE box mod. depending on the size of your cells of coarse.
not to mention that the charger of the eGo has a really low charge rate ,0.42 amps, you may see up to and beyond 24hours to charge anything over 3000mAh.

or make use of a set of Deans plugs(or your choice) within the mod and take the pack out to charge it on your hobby charger.
wiring up a balance plug would make sure that all cells are good , and topped up.

 

[BJ43]

http://www.e-cigarette-forum.com/forum/battery-mods/220307-vvbox-vvpassthru-5.html#post4746422

I have also been in RC electric airplanes, helicopters, cars, trucks, and boats for years. Needless to say thousands of dollars worth of equipment, models, chargers, and batteries. With the correct usage, I have never had a battery burn on me. Batteries are smaller and more powerful than when I got into the hobby years ago. I see me in a rechargeable mod soon.

 

[CraigHB]

I buy the hobby LiPo cells individually for my booster mods and solder them in. I've found only two retail sources for them on the net, BatterySpace and HobbyKing. I use a single cell or 1S as they say.

The tabs are not as easy to solder as something like a thru-hole resistor, but they can be soldered fairly easily with a clean up using fine steel wool and a liberal application of active rosin flux. I "tin" the tabs beforehand, pretty much like tinning a wire before soldering. Just be careful not to use any more heat than you need to. The tabs are insulated with plastic so if you get them too hot, the insulation could melt and the tabs could short out on the cell casing. Don't use anything more powerful than a 25W soldering pencil. Ideally, use a soldering station with temperature control.

That's a good tip on a cell bloating. I've had them bloat myself due to damage and abuse. I discard them immediately when that happens. Same can be said for the round cells.

I've never had a LiPo actually blow up on me. I've done some pretty nasty things to them like accidental shorts and maximum charge rates, typically in testing. They do seem to be fairly tough. Some people will have you believe that's not the case. Though, I'd be careful not to drop a screwdriver accross the terminals or charge one at a really high rate. Also be careful not to puncture them. The casing is only thick foil, not hard metal like the round cells. The cells are made with many layers of thin conductive foil so a puncture can short them internally.

Be careful handling the individual cells. Those tabs are right next to eachother and they can short really easy on something if you don't pay attention to where you leave them. Speaking from experience on that particular issue.

 

[jrm850]

I've got a couple of puffed up packs that I need to destroy. I discharged the last one with a resistor and soaked in salt water, but I think I just want to shoot these with a BB gun to see what happens.

 

[Youssefa]

that is what I would call building "T.I.M." The incredible Machine. The tenergy Buck in the second post has SEVERAL things going for it:

1. large tactile knob for Voltage adj.
2. Volt & amp display.
3. multi in/out terminals (headphone jack and bare wire screw posts)
4. ADDITIONAL USB OUT!!!!!!!!!!!
5. Output goes from 1.25v to 28v
6. Input from 6.00v to 30v < 100ma
THat DOES EVERYTHING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[Youssefa]

I am really just trying to make a "universal portable battery pak" For ego VV and saber touch VV, or any other mod I might get.... for that matter it could recharge cell phones, ipods.....though that part ois not really important. If only I could find this tenergy buck, I think that would do everything I need.

Tenergy Buck
Tenergy DC-DC Voltage Regulator (Adjustable DC-Buck), New! | Battery Superstore

10W Step down
10W Step down adjustable switching voltage regulator | Battery Superstore

 

[Youssefa]

Trust me I have NO of building paks..... the whole point of my project is to build it using as many "retail" parts as humanly possible. This will make it Plug-N-Play, or at the very least a 90% ARF, Not a kit! The hardest part should be how to mount the regulator so there is external access to the knob and still be able to see the display.

 

[BJ43]

The Tenergy regulator is very interesting on the down side is it's size, dimensions: 2.2 x 3.6 x 1.2 Inch is pretty large for just the regulator.