unconventional balance wiring question

[turbocad6]

ok I've been trying to work with maximizing space within a mod to also fit a juice bottle for bottom feeding. the regular 4 prong balancing connector of a 3s pack takes a lot of space, what I have been doing is using a pair of tiny jst plugs instead, but what's obvious to me is that 2 of the 4 wires we're using are redundant. the ground is already at the board and the 3rd cell is also already at the board, both at the battery main connections, I build my own packs anyway so my question is, couldn't I just use 1 small jst for only the cell 1 & 2, and then jump the G to ground at the board and jump the #3 terminal to the battery + right at the board? this will cut down on the amount of wires sticking out of the pack and running to the board by 2 and also reduce the space I need for the balancing plug itself.

if/when I want to charge a pack outside of the mod I could easily make a Y adapter that plugs into the single jst and the main deans connector, and the other end could be a conventional 3s charging plug? I honestly can't see any reason this wouldn't work other than the possibility of the 3rd cell circuit not having as much resistance as the 1 & 2 cells circuits because of the longer thin leads for cells 1 & 2, where 3 is right to the board. I really think it should work fine but figured asking here couldn't hurt

[BobC]

This is why this guy is amazing, I bet if ground is common, it works!

[mandro]

I'm glad that you asked this question turbo. I was thinking along the same lines only yesterday. I'm building a 2s mod and thought of using the boards ground for balancing and then jumping 2/3 on the board leaving just 2 wires to be connected to the battery. If your idea works with the B+ and B- connected directly from the board, I would only need to connect 1 wire to the battery when using a 2s.

[turbocad6]

bob ground is common for sure, I haven't checked it at the board level yet but the G pin on the balance connector may already be connected to ground.

my main concern is with voltage drop to cells 1 & 2, the will both be getting there reference through a long thin wire where cell 3 would be a short jumper from term 3 to bat+, my concern is that cells 1 & 2 may have a certain amount of voltage drop through these longer leads, so showing 4.2 may actually be 4.23, where cell 3 won't have this same voltage drop, this may wind up giving 3 cells that are not truly balanced, cell # 3 may wind up at slightly less actual voltage because of the voltage drop to cells 1 & 2 through the longer leads

[Podunk Steam]

Couldn't you treat it like an AC parallel feeder circuit and even up the wires lengths?

[turbocad6]

I did think of that but then I'd have several inches of a looped wire to deal with. might still be worth it but would be much better and cleaner without it. I might just try it tonight if I get a chance, I can compare voltage in escribe to what I'll measure right at the cells, since there s really no load the voltage drop may be insignificant

[Podunk Steam]

Yeah you're best testing. I don't know what kinda of induction that low a volt and current would create in a loop but I doubt it would be significant.
Edit: Too many variables to play with, different wire insulation, shielded, non-shielded wires... That could be a thought too, use some Belden shielded or similar. 

[turbocad6]

well I tested it and it works fine.

good thing it does too, because I don't have any extra room to add the second connector if it didn't work  this means a 2S can work with only 1 balance wire. I don't know that I'd recommend doing this on a regular install unless space is really tight, but it does work and may be a better alternative than just hard wiring if you don't have enough room for connectors. I like being able to remove the battery











before I run this as a bottom feeder I need to seal it all up. before I seal it all up I'd like to test it and use it a bit to confirm the chip is worth sealing into the mod in the first place. I've damaged a few wood mods already ripping dna40's out of them, so I'd rather burn it in and test it as much as I can before sealing it all up.

I built a test jig for the dna40's when they first came out because I was having so many problems with the first batch of dna40's, I built a few mods and had early chip failures and display glitches so I winded up building a test rig to test the chip extensively before all the work of building it into a mod then having to rip it back out. I still have all my first dna40 pre gold defect chips come to think of it, I still haven't sent them back to evolv yet but coming up on close to a year I better get them in before october   wonder if they'll trade 8 dna40's for a few dna200's, after using these 200's I don't even want to build any 40's anymore    

I'm using the wand and extension from the dna40 tester to test this whole mod and battery, so far it's working perfect. I was even able to offset for the long extension by adding .04 to the base mod resistance in escribe which is pretty cool, couldn't do that with the dna40

[mandro]

Thanks for the info turbo, I'll try this on my 2s build. I've thought about making a DNA200 BF box but I'm finding that I prefer my non regulated BF boxes to my DNA40's.

[BobC]

Nice work Turbo, that's definitely workable

Where do I put my order in?

[scoopy]

That should definitely be "Wall Street" Approved. That's a very good setup..... even us "unworthy common folk" can change that battery so a "CEO" should have no problem

[turbocad6]

Ha, wish that was possible Bob, if I ever hit the lotto then I'd love to spend all my time designing and building mods

As this thing is right now it's not ideally set up for frequent battery swaps but that's only because I'm working within the constraints of an existing mod that's really only designed to hold a bottle and an 18650, if this overall design was modded a bit with an install like this in mind then it could very welll be designed for easy battery swapping though, even a 4 cell design could be done with only adding another 7mm to the width and that would give you battery life equal to a sammy 25r.  Guess the point is that a dna200 bottom feeder doesnt have to be huge really

[BobC]

Only if you have Turbo skillz (and a machine shop),

BTW, you'd be tremendous as a mod builder,

[Podunk Steam]

I think you need some more stuff in that box, like AIR! That is tight in there! Then it looked like the poor tube mods guts were strung out all over the place, seriously taxing my emotions I tell you!
Glad to see it worked out for you!

[Thatguy]

Hey turbo, would you happen to know anything changing the settings in escribe to bypass the balance connector? Someone mentonedmay be a way. I.m running a squonkerwith stacked 18650's and I would like to either wire it up like any other board, pos to pos and ned to neg, or trick that balance plug. 

[turbocad6]

"tricking the balance plug" is a very  bad idea if your thinking of trying to actually still charge the batteries in the mod. you can program the dna to run in power supply mode and then it will work as you want, don't need to trick the plug, but then you can't charge in the mod at all. there's a reason for the balancing leads and that's to prevent overcharging a single cell. if your planning on charging the cells individually and externally then that can work but you still have to match the cells well and keep them in pairs and monitor them yourself, stacking batteries has it's own complications and without on board balancing you have to be more careful because now you are the only monitoring the cells are going to have.

[Thatguy]

turbocad6 said:

"tricking the balance plug" is a very  bad idea if your thinking of trying to actually still charge the batteries in the mod. you can program the dna to run in power supply mode and then it will work as you want, don't need to trick the plug, but then you can't charge in the mod at all. there's a reason for the balancing leads and that's to prevent overcharging a single cell. if your planning on charging the cells individually and externally then that can work but you still have to match the cells well and keep them in pairs and monitor them yourself, stacking batteries has it's own complications and without on board balancing you have to be more careful because now you are the only monitoring the cells are going to have.

Thanks you very much turbo! I am familiar with battery safety, I'm looking to run stacked vtc's. I have a handful of matched pairs that I run stacked in my j board mods. I'm just simply not very educated on the 200. I'm not finding a whole lot of info out there quite yet, This little forum is a prety swell idea tho and I appreciate the help very much. 

[Thatguy]

Thank you so much for the insight, it was so cool clicking 2 buttons and watching my mod come to life much appreciated! Is there any way I can get the board to show me a battery meter now that it is in power source mode. It shows volts under load but it's kinda hard to catch. I haven't gotten to play with the rest is the settings yet. Btw I gotta say I love this big screen, it's fantastic! Thanks again turbo!

[turbocad6]

I haven't actually tried this in power supply mode myself, but you may be able to change one of the default display parameters to battery %, I've got mine set to show battery % on the main display instead of the default voltage since I'm always running in temperature mode but I'm not sure if it'll display that in power supply mode of if it even still references the battery curve and mah info once it's switched over to power supply mode tbh, worth a shot to try I guess. if it doesn't work then this would be something to request here, this may be something that's easy for evolve to add if it doesn't already work as-is

[Thatguy]

Wow, thanks bud, you rock, I'll report back!

[dvandyne2011]

I am planning a build and have most of the details figured out from reading the threads here. This subject is of particular interest as i have not found where anyone has built without using the JST connector. 

My question is...

Can I eliminate the JST connector and just run wiring from the board to the sled? If so, what would the recommended wire size be for such application?

I am planning a 2S build using 2 x 26650's. Space will be tight, i am hoping to never need to charge externally, but to keep the option to charge either way. 

Thanks in advance... 

[dwcraig1]

That should be fine, 24 gauge, equal lengths if possible.

This is showing charger setup but give the proper wiring for the board as well.
Looking at the JST, from left to right 3, 2, 1, gnd

[dvandyne2011]

Thank you. I cant wait to get this one built. Gonna take it slow to be sure i get a quality device put together! Thanks for the help!

dwcraig1 said:

That should be fine, 24 gauge, equal lengths if possible.

This is showing charger setup but give the proper wiring for the board as well.
Looking at the JST, from left to right 3, 2, 1, gnd

[turbocad6]

equal length wires are not necessary here at all. if there was a higher load on these sense circuits then yeah, that would come into play because different wire lengths would affect voltage drop, but here with the balancing circuit it's only being used to sense voltage potential with only a micro amperage potential so differences in length on the order of just a few inches makes no significant difference, if it did then virtually all Digital Voltage Meters would be inaccurate due to the leads themselves. the balance connectors are working similar to a DVM here. of course they're also supplying small amounts of current as a trickle charge to balance, yeah, but a difference in these wire lengths is relatively insignificant here