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Series AND Parallel in one Box Mod

Mr. Pink

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I had an idea for this and found non finished plans randomly around the internet about it and found that BC box mod actually sells a box that can do this, however i dont like that theirs is a 1590B box and from a twisted 420 video seems not have the sides leveled off so i decided to make my own. I figured out a way to fit it all in a 1590G box and still have the option of both series and parallel.
It has a recessed vt 510, a 120 amp MOSFET and the box can handle 50 amps serial and 100amps parallel, surpassing the current limits of battery's when its finished it will have a tactile switch (space for a normal push button), powder coated Tiffany blue and laser engraved.
The reason I post this is bc i was wondering if people think this is a cool idea and if people would, given the option, purchase this?
If i did try to sell them, which i am not currently, it would be probably $100 at most $120
Any comment or suggestions are welcome!
 

david4500

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"surpassing the current limits of battery's" please explain that

also, what DPDT slide switch do you plan on using?
 

Mr. Pink

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i meant that how low you can build is only limited by the batteries not that the box will make you able to surpass your batteries limits.
and i couldnt find a dpdt switch rated over 20amps idk how BC did it maybe by mosfet protecting it but that would require multiple and take up alot of space. so i choose a different method.

what do you think of the Vt 510? i personally have never had a problem with them but i heard that some people have had the delrin melt. maybe they soldered to the wrong piece?
 

Mr. Pink

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yea the only thing i dont like about the fdv 510 are how big they are, with the vt 510, and others with similar 1mm thick top cap, its easy to make it recessed and you cant really do that with a fat daddy. also the space in the 1590g is really limited and even a few mm for a longer 510 cant be spared.

But that's a great way to make it switchable as well i doubt i could fit it all in the G though but from an engineering stand point it looks like a great way to solve the problem.

how much did those 4 components cost you?
 

Mr. Pink

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so if you have 4 mosfets on the board what do you need the other 2 chips and a regular mosfet for?
 

david4500

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The through hole mosfet is just for a size comparison. The 3 boards next to it are all individual boards. Each can be used in a mod. No need to use them together.
 
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Mr. Pink

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thats what i was thinking but i figure i ask encase i was missing something.
so are you going to sell these boards (if so how much) or are you just designing them for osh and they sell the pcb for it?
 

Mr. Pink

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sch.png
that cool as hell, ive been playing with eagle designing one, mines a good bit different. and honestly i dont understand why there are resitors on mosfets bc when i did a scm for a regular series box it said the resistor was meaningless. all i know is if it deosnt work im going to just buy your chip on oshpark
 

david4500

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Try uploading the file to somewhere like http://imgur.com, the pic of your schematic you tried to post just links to a location on your hardrive which others can't see. Curious to see what you've come up with.

My schematic is based on a solid state series/parallel schematic from the guys over at Boxmodders facebook group: https://www.facebook.com/groups/box...tal_comments=355&comment_tracking={"tn":"R9"}

The gate on the mosfet is basically a capacitor. Once charged, it will want to stay on. For the purpose of a mod, that would result in auto firing. Adding a pulldown resistor, the gate charge will discharge to the ground instead of remaining charged and auto firing.
 

Mr. Pink

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i think i did it right now. but in mine i tryed to keep all the amps off the board im not finished with the board but this is where im at. the green that touch are the 510 outs
dQQniC2.png
 

Mr. Pink

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yea i had to change the lbr on it this is what it is now
J5Lx7kP.png
yALdAL4.png
 

Mr. Pink

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will pcb manufactures allow me to have the holes drilled touching like bc i could change it to a bigger size
 

Mr. Pink

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im going to use the same 100a you used, there pretty cheap and i dont see 55amp batteries coming out any time soon

also do ineed p-fets id assume if i did it would be for the series and par+++ since they have neg current going to the gate and pos from the source to drain but i dont fully under stand the difference between the 2
 
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Mr. Pink

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yea that makes since
so would it be limited in parallel 60amps per battery
 

david4500

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Power dissipation is something to consider. Not sure exactly, but package the mosfet is in should hopefully be able to handle 2-5 watts. The value of 104w listed on the data sheet is under absolute ideal conditions, like an enormous impractical heat sink.

(Current^2)*Resistance=Power Dissipation

RDS ON is the resistance value

Power dissipation @ 60 amps

(60^2)*0.002=7.2w

http://www.wolframalpha.com/input/?i=(60^2)*0.002=Watts

Finding the current value that will dissipate 2 watts

(x^2)*0.002=2 watts

x=31.6 amps

http://www.wolframalpha.com/input/?i=(X^2)*0.002=2

Finding the current value that will dissipate 5 watts

(x^2)*0.002=5 watts

x=50 amps

http://www.wolframalpha.com/input/?i=(X^2)*0.002=5

Something else to consider. When connecting batteries in parallel, the total max current discharge shouldn't be considered to double. Consider it to increase by 1.5x. So if you have two 18650s each with a max continuous current discharge of 20 amps, in parallel you can assume the max is 30 amps. Two 30 amp batteries in parallel, 45 amps total...

Basically, I'd limit the mod to 30 amps since that would be the limitation of the batteries in series.
 
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Mr. Pink

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so what would be the actual amp limit in parallel with the p-ch
 

Mr. Pink

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that was my guess but i wanted a sec opinion to verify.
i changed the sch so that the series is a n-channel and parallel+++ is the only p-ch. so if the p-ch true limit is 45amps, does that mean that the brds max in parallel mode is 90amps since the p-ch is only pulling from one battery delivering it directly to battery2+/510+?

i just want the brd to be rated higher than what batteries are rated at right now, a little bit of future proofing
fgwfQ3n.png
 

Saddletramp1200

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I am so thankful people still exist to figure things like this out. I do it as a hobby. Building from memory from the 10th grade. Electronics makes my pee,pee hard. All were doing is making a direct short work for us. Against everything they teach. I like it. ;)
 

Mr. Pink

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Lol pee pee.... Thanks to David for helping me figure that board out, will really make me feel even more satisfied from building my own mod than normal knowing that I designed the chip in it
 

Mr. Pink

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Yea osh is making them so when they arrive I'm going to stress test the hell out of them to figure out its limits
 
Its really cool, I read this entire conversation. I'd really like to find a few tutorials on Box Modding. I buy my own but would eventually like to build my own.

I like the switch box in the G enclosure and BC even said they could do it in a G box, but with all the bells & whistles, with their switch, it gets tedious.
 

jeremypgaal

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David4500 would something like this work for the sx 350 mini board i have been trying to figure out a way to switch from series to parallell but wasn't sure how to do it with the amp limits on dpst switches and such. Could you possibly lead me in the right direction.
 

david4500

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I'm not sure why you would want to do that. Is it for the purpose of charging with a usb board while in parallel?
 
20150625_152022.jpg so i love the idea since ive tried myself to do this with the sx mini chip but only did what i read on another forum david was in i got this. I ended up with 2 battery sleds and slide connectors on the chips + and - and also the battery sleds but one is in series the other is in parallel the chip recognizes each sled with the parallel it reaches only 60 watts and with the series sled it reaches the 120 watts
 
I'm not sure why you would want to do that. Is it for the purpose of charging with a usb board while in parallel?
Well the sx350 mini chip can determine whether there's a single or dual or something in that area and the chip can use both series and parallel batteries so the only slide switch available that can handle the amp limit of the resistance needed to switch between series and parallel is ur own design board at the moment so if it can b applied to the sx350 chip u can see how that would make an awesome mod be able to use both series and parallel batteries also the temp control
 

One2Sicc

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David4500 Could I run a .10 build on dual Samsung 25r cells with the switchable board without killing the board? I'm really interested in getting one.
 

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