[DNA250] Reading just one cell after light fall

[thomasck]

Hi all, I would like some help before contacting evolv. I've been using a dna250 (it had a dna200 and I replaced for a dna250, I don't remember the reason) with a starss player mode 2x18650 for few years already and no issues. This week I've dropped it from the bed side, that is, 40cm max, and in to the carpet. Turns out that after that the mod is dead. It only register one battery like in this thread, and the wiring is the same - https://forum.evolvapor.com/topic/70400-dna200-2-x-18650-not-registering-cell-1/

 

I did all the wiring again, cleaned contacts, lots of flux, wired it all again, and the issue persists, fuse is fine, continuity is fine, make sure the ground with the box is fine, but nothing is helping. 

Please disregard the amount of solder in the battery sled, 

Back of the board - you might say the solder of the b+ is doggy, but that is reflex, I've double checked now after looking at the picture. There's a whole blob of solder in there and the wire is making nice contact

https://i.imgur.com/jEb3tyJ.jpg

battery sled wiring

https://i.imgur.com/60ZMPjf.jpg

front of the board

https://i.imgur.com/Rthco0c.jpg

wiring

https://forum.evolvapor.com/applications/core/interface/file/index.php?file=/monthly_2018_10/Dual_Series_18650_DNA_200_250_Box_Mod.thumb.jpg.2742da6e14aa04f0eb2157dc52404524.jpg

I remember in the past, when I bought two broken triades and they had the same issue, only displaying something when holding the fire button. In both cases I bridged both pin1 with -b and pin4 with b4 like this https://i.imgur.com/4NM9btD.png and both are working fine for around four years - altough I belive I've read this is not recommended. 

Any ideas? 

 

Edited March 27, 2022 by thomasck

[BillW50]

I don't know why you heard it isn't recommended to jumper those two points. Since they came from the same spots on the battery. And many DNA mods are wired just that way anyway (I'd be surprised if the Triade isn't wired that way). And those four connections between the B+ and B- is known as the balance connector (lipos usually has a balance plug on them). If you add the jumper (bridged) for the B- and the closest balance connector connection and do the same on the B+ side, which also has two closest pins bridged (jumpered) for a two cell DNA200/250 mod. If you bridged both ends, you don't need the wires on each end of the balance connector contacts. Since they are the same points as B- and B+ respectfully anyway.

Nor does the balance connections need be be heavy gauge wiring either. Since they don't carry much current. If you bridge them like you did for the Triades, it really shouldn't fix or correct anything since your wiring does the same thing. Unless the one or more of the balance wiring had a break somewhere. Then bridging would correct (fix) it.

Do you have an ohm meter? If you do, those two spots you want to bridge should be 0Ω (shorted) to B- and B+ respectfully. If they are not, there is a break in the wiring going back to the battery.

[dwcraig1]

Jumping the balance connector to B+ and B- is how I wire a 2 cell 200/250

EDIT: It appears that I grabbed the wrong image as this is a DNA 250C but just disregard pin out #4

[thomasck]

@BillW50 I've done the bridge test before with the ohm meter and it reads zero, so the wiring was fine. Even though, I've bridged them but the issue persists. I've checked the software part, making sure two cells are set but I don't know what else to do. Maybe this little fall affected the board in some way that I can not fix myself. 

@dwcraig1 Tried that, no dice.

That's what I get when checking the device monitor,

Thank you both for answering the thread. 

Edited March 29, 2022 by thomasck

[BillW50]

Well @thomasck, I would measure on the board with batteries installed and measure the voltage between B- and B+. That's both cells in series. Then measure B- to that one point alone around of center of the balance connector (orange wire in the drawing). That reads one cell only. Then measure from the same point on the balance connector to B+. That reads the voltage on the other cell. I'm guessing they will all read correctly, but you have to rule it out.

Now if the above reads fine, then it is the board. I would guess the surface mounted BMIC (Battery Management IC) BQ76925 has a connection loose or has failed internally (probably a fractured layer). Without the equipment to deal with it and without experience using it, either hope Evolv will take pity on you or you need another replacement board is my suggestion. I wish I had better news. 

[Wayneo]

1 hour ago, BillW50 said:

I would guess the surface mounted BMIC (Battery Management IC) BQ76925 has a connection loose or has failed

⬆️  That, right there  ⬆️

[thomasck]

@BillW50 Thanks for the suggestion, I even had a glimpse of hope thinking "this is so simple, could be that" killed instantly by "I've done the soldering twice, and in the second time I really reinforced all points, and tested".. But I tried and no luck, all readings are fine. 

If the BQ76925 was not so small and with so many pins, I would try to replace myself as I have a hot air station. Let's see, gonna try Evolv, or just take the board from a Triade I have around and I don't use it. 

Thanks for the help!

Edited March 30, 2022 by thomasck

[BillW50]

I didn't know you had a hot air station. You could try to heat it up until the solder melts and then let it cool and give that a shot. If an internal layer is fractured, the heat might mend it too. But the latter usually doesn't work for long.

[thomasck]

@BillW50 Thanks for the encouragement, I will try that. My experience with the hot air station is limited and I've used just twice (successfully) to replace a lvds chip of a laptop that I have, but the lvds is twice as bigger as the BQ76925. I am going to try anyway, worse case scenario I will get another board for 45GBP.

I will report back!

[thomasck]

Removed the chip, cleaned the pads of the board and of the chip, added solder paste to the board, placed chip, heated up and voilá, the chip moved itself to its own place. But it did not work. Now I am getting 0 in one cell and 4.18V in another lol

Gonna get another board next month, hurts me knowing one of my devices is dead even if I am not using it. 

Thanks you all that tried to help! 

Edited March 30, 2022 by thomasck