Did I kill my overkill 8s BMS? Cells reading wrong voltages, connections verified

[KarlalaSoundsystem]

Hi Folks,

My main negative lead came into contact with a terminal somewhere in the middle of my 8s Lifepo4 battery.

Now the BMS is reading cell 1 as 0.047 v and cell 2 as 4.734v and the BMS is in cell over/under voltage protection mode.

All cells are healthy and reporting ~3.29 when measured directly with a multimeter.

I’ve verified that the balance leads are making a good electrical connection with the wiring harness and unplugged them from the bms and back in hoping a reset might help. Maybe there’s a way to further reset the system?

The symptom suggests that cell 1 is not being read correctly. Perhaps the BMS got damaged or maybe there is something else I can do?

8x eve/lishen 272/280ah cells
Overkill 8s BMS

Thanks in advance!

 

[OnTheRoadAgain]

The good news is that it has an unconditional Lifetime warranty.

No matter what, send it back for an exchange.

If you buy one spare to have on hand, you will never be without.

 

[Deleted member 23531]

Yes you probably fried that sense wire input by it being below ground.

 

[KarlalaSoundsystem]

Ok thanks folks. Now the mad scramble to find a replacement before a gig next week!

 

[Topper]

I'd pull and test your main sensing harness. It is possible 1 or 2 leads got crispy.

 

[KarlalaSoundsystem]

I'd pull and test your main sensing harness. It is possible 1 or 2 leads got crispy.

Unfortunately the harness tests perfectly. Getting expected voltages at each pin.

 

[MisterSandals]

Now the BMS is reading cell 1 as 0.047 v and cell 2 as 4.734v and the BMS is in cell over/under voltage protection mode.

This screams of pin/wire #2 having a problem. If you can look very closely with a magnifying glass at the lead socket and the pin on the BMS you might see an issue. Maybe a blackened surface or something out of the ordinary.

Just a thought.

 

[KarlalaSoundsystem]

This screams of pin/wire #2 having a problem. If you can look very closely with a magnifying glass at the lead socket and the pin on the BMS you might see an issue. Maybe a blackened surface or something out of the ordinary.

Just a thought.

Just tested the voltages on the solder bumps on the bms that come in from the pins and they read correct battery voltages so the problem is somewhere deeper in there.

 

[Deleted member 23531]

so the problem is somewhere deeper in there.

Yeah maybe I didn't give enough detail when I said this:

Yes you probably fried that sense wire input by it being below ground.

Although I haven't torn apart one of these JBD BSMs, I thought they use TI battery monitor chips, which is basically an ASIC with an a analog front end and ADC. So what you did if you pulled a sense pin below ground is forward-bias the ESD protection diodes for that pin, which damages them. You can actually check by doing a load-pull on that pin and measuring the input current as you sweep the voltage. It's not a "wire" problem that you can fix, and likely not a surface-mount component issue either (like a fried resistor). Rather, you likely destroyed a semiconductor device inside the integrated circuit. The only way to fix it is to solder a new component on there, or just return the whole thing under the generous warranty.

 

[OnTheRoadAgain]

Buy another from Overkill quickly (should have done it last week) then send the other one back for exchange when you can. You'll fix your immediate problem and have a spare.

 

[Merlin]

Hi friends,
May I have a similar issue....


Hope you get it fixed Karlala! ??

I got my 16 x 280ah cells 3 weeks ago perfect match from BASEN.
Yesterday I started building my battery pack. First I put them in parallel and try to charge it with my 5 amp bench charger.
The cells was at 3.295v at this time. I wait 2hours and nothing happened on the voltage how I guessed before.
Than I put all cells in series to build a 48v battery and wanted to charge them up so far I can.

(Because Will says in his top balancing video. After that, put it back in parallel and charge them up to 3.6v)

So I build the 48v pack and put the BMS 48v overkill on it. But I made maybe a mistake. I put the first negative on the main negative than on all next positiv pole till the last Red Wire to main positive. Check all voltages on the wire plug. They was all good. 3.29, 6.40, and so on, up to 52.6v
After that I connect the white and the black cable bank on the BMS.
I have a look on them and 3 or 4 cells showing me with roughly -0.07v means completely empty.
I took them all out right away.

I connect all wires new! Exactly like the manual from overkill.
Connect them again without the blue cable and the red load cable to the batterie. Now 2 or 3 cells was not correct showing me.
I connect my charger and all cable and it does work. Showing me all cells as the correct voltage.
So than I charge the battery up to 17h. 7h with 10amps and 10h with 18-22amps.

I set all the settings standard, 280ah nominal and 224ah cycle, the BMS was not show me any errors or other issues, all normal. But....
Now here my concerns:
So I load the battery, the capacity shows me at the first time 134ah with 3.29v, than I reset the capacity one time, than shows me 250ah in the battery. I thought 134ah it's a way to less for fresh delivered cells.
I started the charging. After couple hours was 280ah reached. But charging further, I reset the capacity again. Than shows me 170ah. Reset again, shows me 260ah. I charged them further. I did that maybe 6 times again and it jump everytime back on 260ah after reaching 278ah.
Know I had 272ah and doesn't jump back a anymore after resetting the capacity. Two cells reached 3.65v now. The rest still on 3.390 roughly. Put them back in parallel and load them full to 3.60v further.

Now my questions, is this all normal what happened? how you can see attached the pictures, all the time the cells are in yellow range and the half of the display like 50%. Just shortly before that 2 cells reached 3.5v the colour changed to green. But not the whole box. I saw many videos, on all that videos on the full box colour was green.

Please have a look on the pictures.

Did I killed my BMS in some way? Or a wrong setting or what can be the reason for that?
Very appreciate that when you guys have some answers for me.

Connection verified.

Thank you a lot in advance.

 

[Topper]

The overkill BMS is a smart BMS. It will learn and correct your Ahr capacity through a number of cycles.
My understanding thus far, resetting your capacity will revert the BMS to the factory "best guess" based on the 100%, 80%, 60%, 40%, 20% and 0% capacity voltage settings.
I assume your cells are EVE 280Ahr. I am still mapping my voltage curves, but thus far 3.29V would indicate approximately 63.5% capacity..

 

[OM617YOTA]

Hi Folks,

My main negative lead came into contact with a terminal somewhere in the middle of my 8s Lifepo4 battery.

Now the BMS is reading cell 1 as 0.047 v and cell 2 as 4.734v and the BMS is in cell over/under voltage protection mode.

All cells are healthy and reporting ~3.29 when measured directly with a multimeter.

I’ve verified that the balance leads are making a good electrical connection with the wiring harness and unplugged them from the bms and back in hoping a reset might help. Maybe there’s a way to further reset the system?

The symptom suggests that cell 1 is not being read correctly. Perhaps the BMS got damaged or maybe there is something else I can do?

8x eve/lishen 272/280ah cells
Overkill 8s BMS

Thanks in advance!

Did this ever get solved? I have an Overkill BMS doing something very similar, although it's never been shorted.

Voltage reads fine directly at the cells, at the connector, and at the PCB on the BMS, but the app shows three cells are severely under voltage.

Edit: Overkill already got back to me, I'm just lazy/dumb. I didn't have the main battery negative hooked up, which is apparently needed for proper sensing on the first few cells, and not in the manual. Don't be like me, hook up your system entirely before assuming there's a problem.

 

[Alkaline]

The good news is that it has an unconditional Lifetime warranty.

No matter what, send it back for an exchange.

If you buy one spare to have on hand, you will never be without.

Sorry that is abusing overkill solar, they OP states what he did wrong. Take some responsibility and order a new one.