WIP - 3x 18650 battery box from china -> DNA20 mod....hopefully

[shortyjacobs]

Allrighty all,

I'm in the planning stages of this, and already have hit a mental roadblock - figure some of you professionals out there could help me.

Got one of these: 5V 1A 3x 18650 Battery USB Charger Case Box Mobile Power Bank For Cellphone MP3 -- BuyinCoins.com

Ripped it apart last night and removed the internals. Here's what I'm dealing with now:

Fire button mocked up:

Insides:

dna fits nicely in 3rd battery bay, (I will use 2x 18650s in parallel, third battery bay will house dna, reverse polarity protection, and wires):

Now here's where I need some advice. This is the top of the thing, where I wanna house the fire switch, tact up/down switches, and the 510 connector. You can see the plastic "lid" that was originally there. Problem is, the holes in the plastic lid won't work for me - i can't cover em all up with the 510.

Problem #2, the 510 connector will be mounted into the top plate - so that top plate needs to be *secure*, since it'll bear the weight of a kayfun or other heavy atty...

I was gonna use the plastic plate as a template to cut a sturdier top plate out of metal - thinking either copper or steel. Copper's softer, I was thinking I could bend some tabs into it that would go down into the housing, and then run machine screws into those tabs from the outside.

Alternatively, go with steel, and I'd have to figure out some way to epoxy some magnets inside the housing to hold onto the steel, (would I be able to make something that would have a strong enough magnetic hold to not release the top cap for no reason, but release it when I need to get at the guts?? I don't know).

Any ideas on how I can construct this top cap so I can still get into the guts if need be, but so it's secure enough to hold onto a heavy atty? I don't have much space in there, most of it will be taken up by the 510 connector itself, the switches, wiring, and the positive battery contacts...

 

[retird]

Maybe just cut a replacement top and drill 3 holes... 1 on each corner of the triangle top and matching holes on the case bottom....then take long screws and nuts to hold the top onto the base....

 

[shortyjacobs]

Maybe just cut a replacement top and drill 3 holes... 1 on each corner of the triangle top and matching holes on the case bottom....then take long screws and nuts to hold the top onto the base....

That's a great idea - but I'm short on space. The only way I could do it would be to run the bolts down through the hositive contact holes and use them as the positive contacts themselves....problem is the tops of the bolts would interfere with the huge 510 connector though.

 

[retird]

Pardon my bad drawing but something like this using small diameter screws.... looks like you have room using your 510 connector....

 

[shortyjacobs]

Yup, that'd work, but the other side of the screws would have to poke through the bottom of that top cavity, which puts them in the battery compartments.....the other end of the screws would be in the way of the batteries.

Oh....unless I epoxied a nut down in each corner of the cavity...and trimmed the length of the bolts to *just* the right length.

 

[Cr0tchF4i]

I think the battery idea would work great- get the "natural earth magnets". Those things have insane strength.

 

[asdaq]

How about some tapered head machine screws inserted nearly flush from the bottom, and hex cap nuts on the top?

Also, since the battery springs allow for a lot of slop in battery length, you could build up the contacts to allow for more intrusion in the battery compartment.

Sent from my 4.4'd Nexus 4 using Tapatalk 4

 

[bapgood]

How about swapping the contacts, spring to the top held in place with low profile button head screw threaded into coupling nut. Then make a new top plate and secure it using three screws into the coupling nuts.

Sorry if that doesn't make sense....but its crystal clear in my head

* Edit.....Just noticed those springs don't have a center eye....but the rest still holds true it just wont hold the springs in place

 

[bapgood]

Oh yeah....your connector is to big around....easy....take it out to the lathe and make it smaller

But really its brass so a little dremeling for three screw access notches shouldn't be to bad

 

[shortyjacobs]

Damn, that's a really elegant solution bap. Having a common ground up there would simplify wiring, and the dna20 shares a common ground throughout except the up button, right?

I could easily solve the center eye problem on the springs with a small hold down plate, and the bolts on top could conceivably hold the 510 connector down too, (since, unlike mike, I don't have the means to machine a 22 x 0.5 metric jam but myself). I'll have to see if the geometry works out.

Sent from my phone, ecxuse teh speling mitsaeks.

 

[shortyjacobs]

How about some tapered head machine screws inserted nearly flush from the bottom, and hex cap nuts on the top?

Also, since the battery springs allow for a lot of slop in battery length, you could build up the contacts to allow for more intrusion in the battery compartment.

Sent from my 4.4'd Nexus 4 using Tapatalk 4

I'm afraid the him plastic on the bottom won't have the strength to take a tapered countersink, but this is strongly in my backup option list.


Sent from my phone, ecxuse teh speling mitsaeks.

 

[bapgood]

Damn, that's a really elegant solution bap. Having a common ground up there would simplify wiring, and the dna20 shares a common ground throughout except the up button, right?

I could easily solve the center eye problem on the springs with a small hold down plate, and the bolts on top could conceivably hold the 510 connector down too, (since, unlike mike, I don't have the means to machine a 22 x 0.5 metric jam but myself). I'll have to see if the geometry works out.

Sent from my phone, ecxuse teh speling mitsaeks.

Yep all but the up/pot share the ground.

You could get some brass plate to make your new top plate and then drill it out and solder the brass 510 to it. Not sure how thick they are but lowes and Home Depot (I think on HD) have 4" squares. At lowes they are in the specialty hardware drawers.

 

[shortyjacobs]

Yep all but the up/pot share the ground.

You could get some brass plate to make your new top plate and then drill it out and solder the brass 510 to it. Not sure how thick they are but lowes and Home Depot (I think on HD) have 4" squares. At lowes they are in the specialty hardware drawers.

Yeah, I found a guy on ebay selling copper plates for ~10 for a 4x4. I think it was $11 for a 4x4 1/8, $10 for a 4x4 1/16. He had 4x4s of brass for $14 in 1/8" too.

hrm, Lowes website says they only have 0.010" brass sheets...10 mil is pretty thin.

Would there be any advantage to copper over brass or vice versa?

I'll have to go hunt at hardware stores, (maybe hobby stores?).

The original plastic is 0.053" So 1/16" would be a pretty nice substitute.

ninja edit: what the balls....his 1/8" 4x4" is $11 with free shipping, his 1/16" 4x4" is $10 with $5.15 shipping.....that makes no sense.

 

[bapgood]

If you have any RC or train hobby shops they might have a decent selection, as well as craft hobby stores.

I know lowes has 0.025 copper 4x4 sheets.

Copper vs brass....in this case it would just be looks I would think.

 

[shortyjacobs]

Sweet. Mocked up the M16 Sentinel clone 510 connector in sketchup. Dremmelling out passageways for bolts is doable without cutting into any bad areas....although it's gonna be a tricky sum.........

 

[Alexander Mundy]

Looks like small coupling nuts epoxied in the corners of the top compartment with f head Allen screws through a metal replacement top like retird's drawing with like shaped holes would work well.

I have one of those power banks coming so I have a couple of questions.
How did you remove the top?
Looks like it had tabs sonic welded to the inside of the top compartment?
What is the depth of the inside of the top compartment?

Thanks in advance.

 

[shortyjacobs]

Looks like small coupling nuts epoxied in the corners of the top compartment with f head Allen screws through a metal replacement top like retird's drawing with like shaped holes would work well.

I have one of those power banks coming so I have a couple of questions.
How did you remove the top?
Looks like it had tabs sonic welded to the inside of the top compartment?
What is the depth of the inside of the top compartment?

Thanks in advance.

I removed the top by jamming a small screwdriver into one of the slots in the top and prying, like so:

The top had tabs that are super glued to the inside of the top compartment. My prying busted the tabs.

To hopefully help you further, once you get the top off there's a breakout board with the usb connections on it....this just pulls off the mainboard. The mainboard is then held into the plastic using 3 tiny screws. These 3 tiny screws also attach the top compartment to the bits that hold onto the battery. But when you remove the screws, the whole thing is still held together by this damn metal spear that goes all the way from the center of the mainboard, through the body of the thing, down to the bottom side where it's soldered onto the 3 springs, (hidden by a sticker on the bottom of the battery holder). I didn't realize this, so I just grabbed onto the mainboard and hauled away until I ripped the spear out of the solder blob holding the springs together....you might be able to snip the top solder blob on the mainboard and allow the spear to remain as you pull the mainboard out. Also, the positive battery contacts are on the mainboard, so you'll either wanna glue chunks of the mainboard back in, or use bolts/nuts/whatever as your new positive contacts. Pic of the underside of the mainboard and the negative spear:

Dimensions: a hair over 22 mm deep, 37.25 mm per side

 

[Alexander Mundy]

Thank you very much, that will be helpful!

Look forward to seeing your DNA mod progress to finished.

 

[asdaq]

This pic offers another simpler solution:

There are 2 screws holding the body to the battery cage, how about longer ones that also hold the brass/copper plate down as well. Perhaps there is a third? Those broken tabs can aid in provide more of a lip for the plate too

 

[shortyjacobs]

This pic offers another simpler solution:

There are 2 screws holding the body to the battery cage, how about longer ones that also hold the brass/copper plate down as well. Perhaps there is a third? Those broken tabs can aid in provide more of a lip for the plate too

There is a third screw as well, yup. But they are really tiny holes, and they're just machine screws screwed into soft plastic - I was afraid they'd strip out too easily.