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Breaktru Forum  |  eCigarette Forum  |  Modding  |  Topic: unregulated mosfet box mod wiring question - dual 18650
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Author Topic: unregulated mosfet box mod wiring question - dual 18650  (Read 24344 times)

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Offline windxrunner

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unregulated mosfet box mod wiring question - dual 18650
« on: September 18, 2014, 08:47:32 PM »
what i want to know about is how i'm connecting the batteries. is it ok to solder a wire between the two positive connections, then connect the wire coming from the switches to one and then connect the atty to the other?

if not, how would i go about doing that?

this is a little drawing i made in paint, it's how i'm planning on doing it:



new here, hopped over from ECF to join this board once I became more interested in modding.

EDIT:  red is live, blue is negative, light grey up top is atty, green is a 15k resistor.

Offline CraigHB

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #1 on: September 19, 2014, 02:19:55 AM »
You should fuse each cell individually.  Without it, you have no reverse polarity protection or protection against charge mismatch which can result in unsafe equalization currents.  Of course, if these are non-removable cells it makes the issue moot since it's no longer possible to have charge mismatch or install cells incorrectly.  You also need fuses for short circuit protection.  These top name high drain 18650s are pretty safe, but they're not 100% safe and a short circuit is still a hazard.

Non-removable cells bring rise to another issue.  You mentioned soldering positive terminals.  If you're talking about soldering round batteries on the battery terminals directly, it's very tricky to do it without damaging the cells.  It's possible and I do it myself, but a person has to have top soldering skills to pull it off.  Cells can be overheated and damaged quite easily.  Once a Li-Ion battery has suffered damage, it's no longer a safe battery.  It's actually a much more common practice and much safer to connect cells directly by installing tabs using a capacitive welder.  You can often find top name batteries with tabs already installed.

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #2 on: September 19, 2014, 09:02:19 AM »
First, I wasn't talking about soldering to the cells themselves.

Next, if that isn't the best way to go about it, could you show me a way that is better?

Offline dlv5

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #3 on: September 22, 2014, 05:25:43 PM »
Yeah as long as you have made a connection between your positive connections it shouldn't matter exactly where you place your wires coming off the common positive. All your doing is creating a parallel circuit to the switch and gate.

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #4 on: September 22, 2014, 05:39:24 PM »
Cool!  Thank you!  The last of the parts came in today,,,I'm gonna drill the holes in the enclosure in a few and do all the soldering work tonight!  By the time I go to bed, I'll be vaping on my first DIY box mod!  Whooo!  I'm excited, can you tell?  Lol.  :thumbsup: ;footloose;

Online Dasen22

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #5 on: September 22, 2014, 07:24:27 PM »
Congrats on your first box mod Wind. Nothing like the gratification of making one yourself  :thumbsup:

Offline dlv5

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #6 on: September 22, 2014, 10:38:36 PM »
Awesome man. Post some pics in this thread for us

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #7 on: September 22, 2014, 11:07:49 PM »
For sure, I will. I drilled the holes and started some of the soldering already (which is preeetttyy sloppy, but I think it'll be fine),,,I had to leave to go help someone move something, but when I get back tonight I'll post what I've done so far and then I'll post the finished product once I'm done.

Offline dlv5

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #8 on: September 22, 2014, 11:12:39 PM »
Cool deal brotha

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #9 on: September 23, 2014, 10:19:57 PM »
One of the wires became disconnected from drain tab of my MOSFET during use. The MOSFET got extremely hot after that, burned my finger, so I ripped the batteries out, tearing one of the outer wraps. All the solder jobs were really sloppy, and I was a bit embarrassed of them, hence no pictures. I redid all the wiring today, and I am getting the hang of soldering. But it wouldn't fire... I bypassed the MOSFET and the atty fired up, so I'm pretty sure I wrecked the MOSFET. I think it may have not been ideal for box mods anyway. I ordered another MOSFET that is commonly used in box mods and when it arrives later this week I'll put up some photos.

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #10 on: September 23, 2014, 10:23:09 PM »
That being said, before the disaster happened, the mod was working for a few minutes!  Lol, it was pretty satisfying. I'm not really bummed that happened, though, because the wiring was so bad and messy I would have had to redo it anyway.

Online Breaktru

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #11 on: September 24, 2014, 07:54:06 AM »
Take some time out to practice your soldering technique on wire only until you get the knack of soldering good without having your iron at the solder connection too long. Excessive heat can destroy sensitive components. Use solder flux. Make sure your iron tip is clean and tinned. A temperature controlled soldering station is helpful.

Offline CraigHB

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #12 on: September 24, 2014, 03:32:33 PM »
Using flux makes a huge difference.  Though the solder has a flux core which helps, it doesn't do nearly the job that the addition of flux does (and it has to be rosin flux).  Breaktru mentions using a temperature controlled iron in an optional way, but I don't feel that way about it.  It's pretty much required in my opinion.  You can probably get by with a cheapo pencil for wire to wire joints, but not on wire to circuit board connections or wire to component connections.  It's too easy to overheat things.

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #13 on: September 24, 2014, 03:52:44 PM »
 :thumbsup:yeah, I was not using flux. I've gone through almost all the little bit of solder I bought originally. They have lead free solder at my local harbor freight. Will that work ok?  I'm gonna pick up some flux, too.

Offline CraigHB

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #14 on: September 24, 2014, 09:12:00 PM »
The lead free stuff is harder to work with, has a considerably higher melting temperature.  There are situations where non-toxicity may be required, for instance on the inside of atomizer, but generally you don't want to use lead-free solder unless you have to.  There's a pretty big difference in the ease of soldering between lead-free and tin/lead solder.

There's something call RoHS that requires companies to use lead free solder in production, but it doesn't apply to retail purchase or US production.  Right now it's mainly an EU thing, however, it's expected the US will adobt the RoHS standard soon if it hasn't happened already.  Most US companies comply with RoHS anyway since non-compliance can limit market areas.   

RoHS may make it hard to get tin/lead solder down the road, but it hasn't happened yet.

Offline dravell

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #15 on: September 25, 2014, 08:16:02 AM »
Yeah I wouldnt really recommend lead free for your early soldering endeavors. Since the solder is all contained in the box itself it's not so much of a worry to use leaded solder. Popular 60/40 is a good choice, though my preferred solder is 62/36/2 rosin core silver bearing. It's really expensive compared to standard 60/40 rosin core but I really love the stuff.
A rosin flux pen is a good investment also, along with your regular tub of rosin flux. Flux can make a big difference in how your work turns out.

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #16 on: September 25, 2014, 10:15:31 PM »
60/40 tin/lead is probably the most common.  63/37 tin/lead is fairly common and I like it better since it's a little more forgiving, it freezes faster after you remove the heat.  The melting temps are pretty much the same, I think it's like one degree lower for 63/37, it just freezes faster, the proper term for that is it's eutectic.

The silver bearing stuff can be hard to find.  I haven't actually used the silver bearing stuff at all so I can't say from experience.  It's recommended for PCB work since the endcaps on SMD capacitors and the terminals on ICs can sometimes have silver in them.  The added silver keeps the solder from leaching the silver out of the component terminals.  Though I don't think they often use silver in terminals anymore, too expensive.

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #17 on: September 26, 2014, 11:39:35 PM »
It's sloppy, but it WORKS!



Epoxy is drying ATM, maybe I'll add an action shot of it firing once it's completely dry. I smeared epoxy all around the 510 as far back as I could get it. Idk if you can see it in the picture. How long do you think I should wait before I screw the atty back down and vape her?

Offline Chenderson1985

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #18 on: November 01, 2014, 03:19:10 PM »
What MOSFET are you using for this build? I built a box mod based on your design, and i am getting the proper output to the 510 and the atomizer. When I try to fire it under load I get nothing. Any ideas? I was thinking I must be using the wrong MOSFET.

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #19 on: November 01, 2014, 04:10:52 PM »
Probably the wrong MOSFET. Or maybe a wiring problem. A common problem is one of the grounds is lose. Check all the wires.  But here's a link to the MOSFET I have in mine. http://bit.ly/10c2Gig I have learned quite a bit by making this mod so if you have any more questions I would love to help.

Offline windxrunner

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Re: unregulated mosfet box mod wiring question - dual 18650
« Reply #20 on: November 01, 2014, 04:12:13 PM »
I actually retired this entire box 3 times so I know this style inside and out!

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