Figuring out my next step

[jbotden]

I built 4 battery packs of 18650 cells I harvested from E-bike batteries. Every cell was tested on a LiitoKala lii-500 and charged up to full energy then left to age for at least a month then disposed of if there was any self discharge. Each battery is 7s18p.

I powered up the first two packs after fighting with the Daly Smart BMSs for 3 nights, trying to get them to communicate. The first two worked great and have been all configured now. I get to the third one and the BMS is in voltage error, with the cell voltages like this: 4.1v, 4.0v, 1.5v, 4.1v, 4.1v...

What would you recommend is my next step? Is there a possibility I hook up a power supply to just that cell and charge it up to similar voltage and everything will be fine or am I screwed and should start disassembling the pack now?
Thanks

 

[italianuser]

I'm very interested in your post. I will be at your stage in a month or two, Daly is one of my choices on BMS side. From what you say your third 18p block shows a voltage problem so surely you should check all cells in that block and be sure BMS is working correctly (third probe wire is ok? Did you try swapping the BMSs?). So, if I think of myself in two months time, with this problem I'd be checking the 18p block of cells at 1.5V. If necessary also cutting fuses on one side to make a diagnosis.
(but somebody here might have better advice!).
I'd like to know the problems you encountered to make the BMSs communicate and what solutions you found, you'd save me time when I'll mount them.

 

[jbotden]

I'm very interested in your post. I will be at your stage in a month or two, Daly is one of my choices on BMS side. From what you say your third 18p block shows a voltage problem so surely you should check all cells in that block and be sure BMS is working correctly (third probe wire is ok? Did you try swapping the BMSs?). So, if I think of myself in two months time, with this problem I'd be checking the 18p block of cells at 1.5V. If necessary also cutting fuses on one side to make a diagnosis.
(but somebody here might have better advice!).
I'd like to know the problems you encountered to make the BMSs communicate and what solutions you found, you'd save me time when I'll mount them.

Yes i measured right at the cells and had the same reading so its not a function of the wires or BMS. I didn't use fuse wires but instead the roll of 4 cell wide jumper grid so full on battery destruction is next it seems.
Re BMS, I couldn't get the Bluetooth dongle to communicate at all. Then I went on to the usb-uart cable. It would communicate with the BMS once I downloaded and manually installed the cable driver since Windows couldn't find it. Even though it said connected in the windows program, it wasn't showing any values on screen so I switched over to the Sinowealth BMS tool using the ~F00(don't remember exactly) communication choice and it started talking.
Just remember to change values on screen then hit the Write All button so you don't waste time changing values but not saving them to the BMS.

The smart BMSs all seem to be a pain, I setup a Deligreen 150A 4s LiFePo BMS the other weekend and in that case of 2 cell phones and one laptop only the other person's cell phone would connect. We have chosen smart BMSs in both cases because we intend to run the batteries in Canadian winter conditions and want cold temp protection setup.

 

[italianuser]

Yes i measured right at the cells and had the same reading so its not a function of the wires or BMS. I didn't use fuse wires but instead the roll of 4 cell wide jumper grid so full on battery destruction is next it seems.

Oh that's a pity, but at least now you can proceed with fixing the problem. If you break the battery you could remount it with busbar(s) and fuse wires. It might take some extra effort (buying new pieces) but next time you have an alert it will be easier to do maintenance.

Re BMS, I couldn't get the Bluetooth dongle to communicate at all. Then I went on to the usb-uart cable. It would communicate with the BMS once I downloaded and manually installed the cable driver since Windows couldn't find it. Even though it said connected in the windows program, it wasn't showing any values on screen so I switched over to the Sinowealth BMS tool using the ~F00(don't remember exactly) communication choice and it started talking.
Just remember to change values on screen then hit the Write All button so you don't waste time changing values but not saving them to the BMS.

The smart BMSs all seem to be a pain, I setup a Deligreen 150A 4s LiFePo BMS the other weekend and in that case of 2 cell phones and one laptop only the other person's cell phone would connect. We have chosen smart BMSs in both cases because we intend to run the batteries in Canadian winter conditions and want cold temp protection setup.

Nice to know this stuff, not a fan of bluetooth! For now I'm checking out reviews and trying to gather info on 100-200€ (or $) BMSs. One of these nights, most probably around 2AM I'll buy first two units and post a photo here in the forum!
Thanks for sharing JBot, I'll follow your updates