Welp, Lowes only had 0.010" brass (for $4), or 0.025" copper, (for $9). Neither was an attractive option. Instead of paying $15 for a 4x4" 1/16" sheet on ebay, I got one from AmazonSupply. A 3x12" sheet, 0.063" (1/16"), was $13 with free Prime 2-day shipping. I'll have it Saturday. Yay!
WIP - 3x 18650 battery box from china -> DNA20 mod....hopefully
- Thread starter shortyjacobs
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So I had a new thought last night - reverse polarity protection.
I'd planned on using the SI4477dy MOSFET milo found in her reverse protection thread. My thought was to hook it up after the two batteries, treating them as a 1S2P battery pack, like so:
But here's the problem - I'll be removing these batts to charge em, (don't think I'll use an onboard charging port, so not even putting one in). The risk of me putting BOTH batteries in backwards is pretty low, but the risk of putting in ONE battery backwards is significantly higher. In that case, a single MOSFET afterwards won't do diddly to stop the two batteries from shorting out each other and melting down real quick, (it'd be a 7.4v nominal short).
So I have two plans on how to fix it, and am looking for input from all of you pros:
Plan #1 - Use two MOSFETs, one for each battery. If either battery is inserted backwards, that battery's MOSFET won't trigger on, and the DNA will only pull from the correctly inserted battery.
Plan #2 - Use a PTC fuse to prevent a feedback short circuit between the batteries if one is put in backwards, and a MOSFET to prevent both from being inserted backwards.
Any comments on which might be better? Will I see more of a voltage drop from plan #1 or plan #2? I'm thinking plan #2, since plan #1 is essentially two voltage drops in parallel, and plan #2 is two voltage drops in series. Also, in plan #2, the one battery "behind" the PTC will see more of a voltage drop than the other battery "in front" of the PTC, so my batteries will discharge unevenly...
I like Plan #2 for it's simplicity, and plan #1 for it's robustness and for keeping discharging batteries balanced. What say you?
edit: ...., plan #1 won't work as drawn, will it? Here's what it looks like with one reversed batt:
What will happen here? I have a wire going from the neg of one batt to FET1 Gate, and from the positive of the other battery to FET2 Gate, but those wires are also connected to each other.....Do both FETs fire, does neither fire? does the whole thing melt down? I really don't know much about how FETs work.
I'd planned on using the SI4477dy MOSFET milo found in her reverse protection thread. My thought was to hook it up after the two batteries, treating them as a 1S2P battery pack, like so:
But here's the problem - I'll be removing these batts to charge em, (don't think I'll use an onboard charging port, so not even putting one in). The risk of me putting BOTH batteries in backwards is pretty low, but the risk of putting in ONE battery backwards is significantly higher. In that case, a single MOSFET afterwards won't do diddly to stop the two batteries from shorting out each other and melting down real quick, (it'd be a 7.4v nominal short).
So I have two plans on how to fix it, and am looking for input from all of you pros:
Plan #1 - Use two MOSFETs, one for each battery. If either battery is inserted backwards, that battery's MOSFET won't trigger on, and the DNA will only pull from the correctly inserted battery.
Plan #2 - Use a PTC fuse to prevent a feedback short circuit between the batteries if one is put in backwards, and a MOSFET to prevent both from being inserted backwards.
Any comments on which might be better? Will I see more of a voltage drop from plan #1 or plan #2? I'm thinking plan #2, since plan #1 is essentially two voltage drops in parallel, and plan #2 is two voltage drops in series. Also, in plan #2, the one battery "behind" the PTC will see more of a voltage drop than the other battery "in front" of the PTC, so my batteries will discharge unevenly...
I like Plan #2 for it's simplicity, and plan #1 for it's robustness and for keeping discharging batteries balanced. What say you?
edit: ...., plan #1 won't work as drawn, will it? Here's what it looks like with one reversed batt:
What will happen here? I have a wire going from the neg of one batt to FET1 Gate, and from the positive of the other battery to FET2 Gate, but those wires are also connected to each other.....Do both FETs fire, does neither fire? does the whole thing melt down? I really don't know much about how FETs work.
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My mind is working slow this morning, but I don't think plan #2 would work because wouldn't that basically be wiring the batteries in series?
I like the simpler and zero added resistance type method like used on FT battery holders....contacts that wont contact if the battery is installed reversed.
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My thought with plan 2 is if one of the batteries is installed backwards, (forming a circuit between the two batteries, the PTC will quickly heat up and "trip", breaking the circuit. If the batteries are installed correctly, they'll still be in parallel.
Will plan #1 work? see my edit above...
There's a third option too....go with my original idea, and put in hot springs for both batts. In the event of one batt installed backwards, the hot spring collapses and all is well....
HeliX hot spring - Avid Vaper
I commend you on choosing the right material for the plate. 
Also, since you are building this mod, aren't you likely to always remember which way the batteries go in, especially when associating the spring needs to go on the negative end? I could see the reverse polarity protection as advised for a mod one purchases, but you do get quite intimate with how it all works if you actually make it.
That is a lot of extra wire your are looking to get into.
Also, since you are building this mod, aren't you likely to always remember which way the batteries go in, especially when associating the spring needs to go on the negative end? I could see the reverse polarity protection as advised for a mod one purchases, but you do get quite intimate with how it all works if you actually make it.
That is a lot of extra wire your are looking to get into.
I commend you on choosing the right material for the plate.
Also, since you are building this mod, aren't you likely to always remember which way the batteries go in, especially when associating the spring needs to go on the negative end? I could see the reverse polarity protection as advised for a mod one purchases, but you do get quite intimate with how it all works if you actually make it.
That is a lot of extra wire your are looking to get into.
The batts I plan on using, NCR18650PDs, are flat tops. They look pretty damn similar top and bottom.
It's true - I probably won't insert them backwards - I've yet to do so on ANY mod of mine.....but I just don't want to put all this time and effort into this mod and fry the damn board. It's kinda snowballed...I figured the reverse polarity protection FET was a simple addition, but it's gotten more out of control as I realized I had two batteries in parallel to worry about.
I'm half ready to ditch the whole mess, just throw a couple of hot springs in there to guard against accidental reversal of one of the two batts, and hope I never insert both of them upside down....
I told you my head was foggy this morning.....disregard my comment about series
So I think plan #2 would work and you might be right about plan #1.....but I don't trust myself right now so I'm not helping
Regardless I hope your planning on mocking this up before putting it to use.
Allrighty, screw the reverse polarity idea. asdaq is right - it's a lot of extra wiring. I'm still afraid of reversing the polarity of ONE of my batteries though, (I really doubt I'll accidentally install both wrong, but I could see accidentally putting one in wrong). While it won't necessarily fry my DNA20, (though it still could) , I don't like the idea of shorting one battery with another - that could make a nasty mess...So I'm gonna go the PTC route. I realized that I can just put a PTC on each battery, and then they will see equal voltage drops, and won't discharge unevenly.
Like so:
Easy, breezy, beautiful.
Like so:
Easy, breezy, beautiful.
Allrighty, screw the reverse polarity idea. asdaq is right - it's a lot of extra wiring. I'm still afraid of reversing the polarity of ONE of my batteries though, (I really doubt I'll accidentally install both wrong, but I could see accidentally putting one in wrong). While it won't necessarily fry my DNA20, (though it still could) , I don't like the idea of shorting one battery with another - that could make a nasty mess...So I'm gonna go the PTC route. I realized that I can just put a PTC on each battery, and then they will see equal voltage drops, and won't discharge unevenly.
Like so:
Easy, breezy, beautiful.
Sorry to rain on the parade but reversing the polarity will harm the DNA rather easily. And if I understand what your thinking it wont help if the first battery you put in is wrong, the damage will already have been done.
Yup, I'm aware of that - I'm more afraid of batteries blowing up.
hum.....how about this idea......build in an evolve usb charging board.... then ya just need to replace the batteries when they wear out......
OK, so after a long consideration, I'm giving up on reverse polarity protection. On to more fun things! (AKA - super pic heavy update post)
My Brass arrived! I could make a lot of top caps out of this:
Traced out my part and cut it out:
Dremeled out reliefs in my sentinel top cap, (this took a WHILE.....took me maybe an hour to do the first one - did you know grinding brass doesn't work? It just clogs the grinding stone and causes it to explode....bad mojo). Once I figured out my system, the 2nd and 3rd reliefs took only a minute.
Shined it up, ready to solder!
All my shining was useless, soldering apparently turns gold to poop:
New negative posts are in:
Couldn't find brass coupler nuts, (in fact, couldn't find any coupler nuts in 10-24), so used these furniture nut thingies:
Top cap is in!
With an AGA-T2 on top, next to the Sentinel that donated it's brass top cap, (sentinel in 18650 mode):
Coming together - now to do all the wiring
My Brass arrived! I could make a lot of top caps out of this:
Traced out my part and cut it out:
Dremeled out reliefs in my sentinel top cap, (this took a WHILE.....took me maybe an hour to do the first one - did you know grinding brass doesn't work? It just clogs the grinding stone and causes it to explode....bad mojo). Once I figured out my system, the 2nd and 3rd reliefs took only a minute.
Shined it up, ready to solder!
All my shining was useless, soldering apparently turns gold to poop:
New negative posts are in:
Couldn't find brass coupler nuts, (in fact, couldn't find any coupler nuts in 10-24), so used these furniture nut thingies:
Top cap is in!
With an AGA-T2 on top, next to the Sentinel that donated it's brass top cap, (sentinel in 18650 mode):
Coming together - now to do all the wiring
Big huge pic update time (spoiler alert, it works!!!)
Well, first off, the damn batteries wouldn't fit in the mod, because although the spring provides a lot of slop, the machine screw heads were just too deep. So I ground them down and put it back together:
Positive posts made by coiling some wire and soldering it into a pad:
Inside of the top compartment, switches epoxied into place, (the typical silver dome tact switches everyone uses, but I got ones with contact posts coming off the side, instead of off the back, to fit better). Edit: oh, and you can see that I had to solder the wires onto the screw lugs on the FIRE switch.....the only way to get the switch in was to screw the switch into the stationary nut, and no matter how much I tightened the screws on the wires, all the twisting would cut them loose again. Ended up pretinning the screw posts, installing the switch, fishing pretinned wire up through the body, and soldering it in place inside the cap. That was tricksy...
Most of the wires ready to connect to the DNA20, (didn't have the pos lead from the 510 connector in yet...it went in right after I snapped this), oh, and big thanks to someone here, (I think Mike or bap?), for the tip that almost all the grounds are shared on the DNA20 - as you can see, I don't have many black wires):
Plenty of "oh god, oh god" moments during the final solder in - made the mistake of pretinning the pads, which meant all the holes filled in, which meant I couldn't poke wires through....then tried to desolder them, only partially succeeded, and finally soldered the Down + wire into the Down - hole, which meant I could only increase power, not decrease it....but I finally got everything soldered in correctly, and it has life!
Gooed in some gel epoxy:
Flush enough!
Window cut into case, (you can see the power UP and DOWN tact switches here too):
Can hit the power UP and DOWN buttons with thumb and forefinger while looking at the display:
Complete! Size comparison with my nemy clone:
A huge thank you to everyone who helped me out, and to others whose theads I lurked. This thing rocks!!
Well, first off, the damn batteries wouldn't fit in the mod, because although the spring provides a lot of slop, the machine screw heads were just too deep. So I ground them down and put it back together:
Positive posts made by coiling some wire and soldering it into a pad:
Inside of the top compartment, switches epoxied into place, (the typical silver dome tact switches everyone uses, but I got ones with contact posts coming off the side, instead of off the back, to fit better). Edit: oh, and you can see that I had to solder the wires onto the screw lugs on the FIRE switch.....the only way to get the switch in was to screw the switch into the stationary nut, and no matter how much I tightened the screws on the wires, all the twisting would cut them loose again. Ended up pretinning the screw posts, installing the switch, fishing pretinned wire up through the body, and soldering it in place inside the cap. That was tricksy...
Most of the wires ready to connect to the DNA20, (didn't have the pos lead from the 510 connector in yet...it went in right after I snapped this), oh, and big thanks to someone here, (I think Mike or bap?), for the tip that almost all the grounds are shared on the DNA20 - as you can see, I don't have many black wires):
Plenty of "oh god, oh god" moments during the final solder in - made the mistake of pretinning the pads, which meant all the holes filled in, which meant I couldn't poke wires through....then tried to desolder them, only partially succeeded, and finally soldered the Down + wire into the Down - hole, which meant I could only increase power, not decrease it....but I finally got everything soldered in correctly, and it has life!
Gooed in some gel epoxy:
Flush enough!
Window cut into case, (you can see the power UP and DOWN tact switches here too):
Can hit the power UP and DOWN buttons with thumb and forefinger while looking at the display:
Complete! Size comparison with my nemy clone:
A huge thank you to everyone who helped me out, and to others whose theads I lurked. This thing rocks!!
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Oh, and I still need to put a window on that cutout for the screen. I was gonna use some 10 mil PET or polycarbonate around the inside radius....trying to figure out how to easily glue it in, since it's down in the bottom of the case....should conform to the curve nicely if I can do it without getting glue all over the bit I wanna look at.
Edit: Also, not sure if I said this already, but using 2x NCR18650PD batts in this, in parallel of course. 5800 mAh baby!
Edit: Also, not sure if I said this already, but using 2x NCR18650PD batts in this, in parallel of course. 5800 mAh baby!
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Not really worth taking another pic, as it won't even show up, but I got my window put in, so now I can take the premask off of the display. I used some unbelievably strong double-stick tape. I cut a piece, carefully applied it to the inside of the white case, and then cut through from the outside through the cutout to remove the tape from the window part. Then I put in a piece of 10 mil PET film. Perfectly clear, recessed, and it'll keep all the pocket lint out.
So far, using this exclusively with a 0.9 ohm Kayfun 3.1 clone, I'm down to about 3/4 batt, at a guess.
Should I be going higher resistance with this thing? I've been out of the world of VV/VW for too long....What's better, more wraps of 28 ga, or going up to 30 awg?
So far, using this exclusively with a 0.9 ohm Kayfun 3.1 clone, I'm down to about 3/4 batt, at a guess.
Should I be going higher resistance with this thing? I've been out of the world of VV/VW for too long....What's better, more wraps of 28 ga, or going up to 30 awg?
Really dont think your ground connection is a cold connection. LOL wow thats transferring the electrons..
Like it I do..
Like it I do..
I'm confused, are you saying you think my ground connection IS a cold connection? It's not great, but it's better than it looks, and it's definitely flowed in......it was a 3 stage solder, and my iron was overloaded with solder to boot, so I got some funky peaks. I gave it some hard yanks though, it's solid.
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