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unbalanced cell ?


David247
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def something going on with mine today...


I noticed the day before yesterday that it only charged to ~97% instead of 100%, but I used it all day yesterday with no problems then plugged it in to charge last night, didn't pay too much attention to where it was at exactly, but usually by the end of the day I'm in the 30% range give or take.

this morning I woke and it was only at 69% and was charging at less than .1a,tried another charger and same thing so hooked it to escribe to see cells 1 & 2 were at 4.20v while cell 3 was at 3.79v...

I've never blown a fuse or had any kinds of major issues with this thing, a few times I noticed that it would only charge to 99% instead of 100% but never really thought much of it. I tried to recover the cell by charging it by itself and got it up to over 4v by the time I had to leave and I'm vaping it today and will see where it's at tonight but this is weird, why would 2 cells charge to full 4.20 while the third didn't charge at all? it obviously charged so I don't know what to think..




  


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SSV said:

here is the same pack, freshly peaked on an external balance charger......and verified to be in balance with an external meter.....

dna/eScribe reads it as this though.....

imbal2.JPG 

Something is obviously wrong with the cell measurements. Can you post a pic of whatever setup it is you're using to get those results? I'd also suggest that while it's doing that, measure each cell voltage across the balance connector pads on the board itself as well as the pack voltage at B+ B- with a decent DMM. For a freshly charged non-defective pack, if something were actually sagging one cell that much, the magic smoke would be released somewhere. You have to either have garbage in at the balance connector (why it would help to see what you have built along with actual measurements of what the board is getting on its side of the connector) or something wrong with the board. Last but not least, it is odd that it shows 0 Wh charge for an 11.94 V pack. My guess is it from the anomaly it sees on cell 3. As a possible red herring but I'll ask anyway, what are your pack settings in the mod tab? Anything unusual?
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both units were cleaned and inspected under the microscope for bad solder joints on the balance/charge circuitry....there are no visible faults.  I am going to reflow the boards just to confirm that.  The collection of SOT parts for the balance circuitry are directly under the B+ solder pad.  That seems a bit iffy, if an end user applies too much heat to the B+ solder pad and doesn't use any kind of heatsink it's entirely possible to cause some issues there.....BUT one of these units worked fine for over a month, and then just randomly started exhibiting this behavior. 

Both packs were verified charged and balanced on an external meter.  Both dna200 boards were cleaned with appropriate cleaner, and inspected for bridges etc.  On that note the conformal coating on the boards is not the best I have seen.  Boards contaminated with e-liquid (inevitable in some designs) are showing signs of the conformal coating failing....

This has to be a monitoring error, either caused by software, or a component level failure (although microscope inspection shows nice clean fillets on all solder joints).  4.35 V is simply not gonna happen w/o some serious input failure....as you said the magic blue smoke would have been released if this was happening. 

I don't really feel like getting the micro probes out and checking voltages across all those SOT pads, but I guess that is the next step. 

Before you break out the expensive micro-probes and make your eyes dizzy under a microscope lol, did you use a pair of ordinary meter probes to actually measure what the balance connector is seeing? The pads the balance connector are soldered to are pretty big. Trouble shooting 101. Start at the beginning. Also, your setup sounds . . .unconventional. Can you post a pic of what you are actually using to obtain the results you posted?
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SSV said:

[.....I am assuming the balance inputs use a tunnel diode to prevent reverse biasing, so if the USB connection shorted and threw current against those diodes, that could explain some of this behavior....but speculation can run wild in these types of scenarios, so I would rather test, than assume....

Yeah, test the tunnel diodes you think would be on the balance inputs. I think I see why you might be so frustrated. Uh boy . . . I should have seen this coming. Good luck with your venture. I'm sure you will succeed because after all there's one born every minute, right?

image.jpg

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scoopy said:

My setup with a MaxAmps 2250 has been fine for months and now cell 3 seems to be draining more than the other 2....It charges back fine but when u take a puff with device monitor up u can see cell 3 gets lower.... .any ideas anyone?

Do you have another pack to test with? Might just be a bad cell. When you say lower, how much lower?
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SSV said:

 Boards contaminated with e-liquid (inevitable in some designs) are showing signs of the conformal coating failing....

 



can't help with the other issues you're having but as far as the conformal coating I've noticed the same thing since even the dna20's.

I've spoken to brandon in the past asking about what I could coat the board with to waterproof it and he said it's already conformal coated and shouldn't need anything else, but e juice is not the same as just moisture, and it seems e juice really eats through the conformal coating and any time I got even a little e juice on the board usually the first thing it did was knock out the display. I'v been using these things in bottom feeders since the dna20's and that's one of the biggest problems of mixing a dna with a bottom feeder. I've lost several dna20's and 30's to e juice, then I started coating them myself to seal them better and so far that has worked out well for me for the most part, only problem is once I coat them I then can't warranty them if I have any other problem. the 20's and 30's were fine though because they were rock solid and reliable, once they were coated they just didn't ever fail, until the 40's that is...

I've lost a few coated 40's to problems other than e juice damage and those I just throw away so I've been now avoiding coating 40's unless I really have to in the design like when the chip is right under or next to the juice bottle . now I would love to fully waterproof one of these 200's but I'd hate to then have a problem with the board because then I just have to throw it out so I'm waiting till I hit like 10,000 puffs and if the chip is still going strong, then I'll try waterproofing that 200

here's a dna30 I did a long time ago and it's still going strong till today and I've wetted it many times since then and even had several e juice spills in this mod from time to time with no problems at all, I'd love to do this with a 200 soon but like I said then all warranty goes out when this is done really


[video]https://www.youtube.com/watch?v=LfepY3gTpDA[/video]
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I have a problem.....my cell 3 is always.03 to 0.04 lower than the rest.Though I know this is fine my cell 3 will only charge to 4.17.I ordered a power resistor and was wanting to do the battery analyser to finish all the other adjusting the chip allows (case thermal properties and mod resistance) but when I go to do it I can't because it says battery is not full...James or John is there any other way to do this....I have a MaxAmps 2250 in it.....All I know to do is call MaxAmps and request a new one since it had a lifetime warranty but don't know they will want to with this little of a difference. ...Any suggestions? *edit tried a fully max 900 and when I installed it it was balanced and charged to 4.20 on each cell After I used it and went to recharge cell 3 is lower again and will only charge to 4.17 I can't do the battery analyser because it will keep saying battery is not full

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I got mine lined back out. Evidently the solder points for the balance port got all black and corroded looking....I'm thinking it was from the flux not being cleaned off after installing the port.....I cleaned them all up with alcohol and it looks like new.....I put it all back together and it took a while but it finally balanced back out.I keep checking it as I vase on it and the battery drains and it's staying balanced

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mine has been driving me crazy, even when I do get it to balance out perfect it's short lived and still winds up going out of whack again and again, and it's always cell 3 that seems to be the problem. I've been trying to document it with pictures when I have the time and here are some to show what I mean.

first, here is where it was several days ago. also notice that cell one is above 4.20, @ 4.21 while cell 3 is very low

 




now eventually I got it to balance out again, but while in use and discharged somewhat:




but then eventually the problem returns, here is where it winded up after an 8 hour charge:







then, yet again I got it to balance out eventually and then this is where it winded up again one morning after an 8 hour charge, balanced but wouldn't charge all the way to 4.20




then the next day I winded up with this after charging overnight. how can this show as only 99% ??




and now this morning I'm back to this:






it's just crazy, some days I wake to 100%, some days 99%, some days 97% and some days 94% and this is always after ~8 hours of charging 

I've been wanting to finally seal this chip up but with the way it's acting here I just can't seal it up. other than these charging problems the chip has been working fine so I don't know what to do.

one thing I've been considering as a trouble shooting method is to take the 3S pack apart and re orient the cells, moving cell #3 to a different spot in the series to see if the problem follows that cell or remains on cell #3 to be sure if it's a cell problem or a chip problem but I haven't had the time to do that and honestly I don't think it's the cell.

this is driving me absolutely nuts. this is my first build I've been testing for over a month now and has been working fine except for this charging problem. I have 3 more chips I got with this batch and I just ordered 20 more chips to start building mods, but it's hard to have confidence in investing so much time money and effort into building more mods when I'm facing a problem like this. I don't know what to do here... anyone from evolve reading this, please...   help!!!   :D

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well the more I play with this day after day the more I'm becoming convinced that the problem is the battery pack itself. I'm going to build a new pack for it this weekend. I wonder what the threshold is for the chip to show an imbalanced battery msg? all through this the chip never really complained about anything or showed any indication of the imbalanced battery even when it winds up almost 1/2 a volt off from each other

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