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Discussion Starter #1
I was doing some top balancing on my bank the other night and suffered a brief transient from alligator clip wiring. Now every time I close the contactor a warning comes up and I have to push the reset switch ever 30 seconds or so.

All the wiring looks good and all the cell modules light up like they are supposed to even registering the event on the first cell of the bank with a Long Pulse all OK, but HVC or LVC happened in last 30 min or with a Rapid Flash HVC condition according to how I am looking at the LED indicators.

Perhaps someone has gone though this before. My first time in 9 years with this 400ah 16 in series pack. It was originally made by Balqon so the BMS may very well be the HiQAP BMS as installed.

I have the documentation for both but I am coming up with very little to go on here especially for spare parts. Even a work around would be handy to bypass the event like wiring the NO to NC.
 

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Discussion Starter #2
So I closed the cell loop with a short piece of wire and was able to use the bank. The rest of the boards still seem to be doing there thing as the bank is all perfectly balanced at 3.28 volts and on the way down now at 52.2 volts.

What I found after the fact... When I tested all the cell boards by putting the voltmeter on the spade connectors on each board all boards have no continuity or the voltage reading is dead on 0.00 and it reads that instantly.

All the cell boards except one that is. I cleaned it up with some compressed air and checked everything on the board that I can while testing it. I can get it close to 0.00 but I still think this board is toast.

I am not sure if this is how you would differentiate a voltage variance in a Normally closed loop. The head board must be sensing a slight open current on that cell and tossing the error.

As much as I hate to try it I will go back and put the cell loop wires back into the headboard and see if it still issues the error. I do not know the tolerance it has or if it would be any open in the circuit causes an error no matter how small.
 

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Everything arrived for the project. A box full of 20+ miniBMS boards. Box of spade connectors, box of butt connectors, two feet 18 gauge wire, fifeteen feet of one and a quarter inch black wire loom, Bag of D-Clips for same to clean up solar, PSC-6916 bench top power supply. That was it for shopping today. https://www.rpelectronics.com/psc-6916.html

The boat is hotter during the day so will start by replacing the cell board that I believe is bad in the evening. I should be able to do this with the bank disconnected without even loosening a battery post.

Remove small bolt and nut on bad and good cell board. Attach good cell board to battery. Prep red wire for cut and crimp with butt connector. Attach wires to spade connectors and test. This will require attaching the cell loop wires back into the head board by the main contactor - There is a lot of energy held back in that contactor.

I have never installed a miniBMS system so if this is contrary to how it would be done I guess I will find out soon enough. Although the last thing I would want to do is short out the bigger board downstream of the cell module.

So I will take the afternoon to review any of the documentation on installation of the a miniBMS system for safety sake. I plan to have a functioning BMS again soon and that will be a relief.
 

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Discussion Starter #4 (Edited)
Replaced the cell board with new old cell board and the BMS is so far back online. I have two cells that are not the same voltage as the rest of the cells. I intend to verify any weaker cells when my pack voltage is around 50.7 volts and on the way down. I will then note which cells.

The old style cell board and the new style cell board are for the most purposes the same. The newer ones being more energy efficient. I could care less where it shunts as the bank is never that full ever. So long as the mixed system will still report a low cell and disconnect the load is the most important in this application.

Next I will charge the bank as full as I can get it. I will look for cells that are behind the 3.6 volts per cell. After noting which cells are visibly behind say 3.4 volt compared to 3.6 volts I can then throw the main disconnect.

Disconnect the BMS Deutz plugs. Separate the two halves of the 16s bank of 400 ah cells. Further discuss why I would do that when the main ground for the system is at cell 1 and the positive is at cell 16. There is a nice custom cable that adjoins the two cases of cells on the negative posts of cell 8 and 9. I see no reason to separate the bank at 8 and 9 and loose the ground on 1.

So then with contactor closed I will just proceed to cell 11 and disconnect the negative terminal first and then move on to the positive terminal and then separate it from the 10 and 11 cells either side.

I have never had to split a bank this big. Are there any other precautions I should follow and am I doing it right?

Once the cell is isolated I can begin to charge with the PSC-6916 power supply. I have to continue to study that but I have a little time. The biggest question I have is about this shorting the leads stuff to get the voltage. Perhaps just never having done it before.
 

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Discussion Starter #5
I continue to struggle with this BMS today. After having replaced the cell board that showed OL or 0.11 volts with another older miniBMS module that when placed on the battery showed 0.00 volts so I thought I was good to go.

I brought the pack down to 50 volts this morning and waited for a LVD to occur and it did. I thought I was good to go and problem resolved and on to top balancing.

No sooner than 20 minutes later the bank starts to fault and now I have two more cell boards that register voltage across the spade connectors. I thought this had to be a normally closed loop and that voltage can't be present across the spade connectors. Or am I measuring something else across the spade connectors.

The two that are showing voltages are on a cell that is at 3.27 while the others are at 3.31 volts. So am I measuring some type of balancing current here? Are the cell boards bad. No warnings or alarms are coming on. I have two chargers running into the bank and producing 30 amps more or less. I can turn the solar on as well for more charging amps.

I wanted to bring the bank to full charge and then take care of the two lagging cells buy balancing them with the bench top power supply up to 3.6 volts when the rest of them are fully charged. So long as I can get them closer was the goal.
 
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