51.2 v 100ah Battery pack from china, no instructions, BMS is a pain in the butt

[dieselenvy]

Can anyone give me some info and maybe help me trouble shoot this thing. Anyone know what the dip switches do?
It arrived charged at 52.5v. It seems to take a long time and a lot of power to but it fully charged. Which 16 x 3.65 is 58.4v. Please lmk if I am mistaken.
The BMS shuts the battery off at 50.4v. The BMS is really a pain. I'm hoping someone can help me better use this one or if it's better to just replace with an overkill unit. I've also noticed that the voltage at the output doesn't match the voltage at the cells. For instance voltage at output may read 56v and 3.125 at the cell. Thanks in advance

 

[MisterSandals]

The BMS shuts the battery off at 50.4v.

Is there any indication as to why the BMS shut off?
What are the voltages of all the cells when it shuts off?

I've also noticed that the voltage at the output doesn't match the voltage at the cells.

Have you tested the voltages at the connector to the BMS? Cell 1 is the negative so testing against cell 2 should be about 3.2v. Cell 1 & 3 should be ~6.4v ... and up to cell 16 which has to be the same as the battery voltage. If there are any gaps or uneven voltage jumps, you've identified bad connections or cells.

 

[dieselenvy]

All the cells read between 3.1 and 3.24 except one cell is 2.5. This cell needs replaced? Any insight on a good place to purchase one? The entire bank is showing 51v but the BMS won't allow the battery to "turn on". It's only sending 38v to the terminals.

 

[MisterSandals]

This cell needs replaced?

It looks suspect that is for sure.

It's only sending 38v to the terminals.

I don't know why a BMS would only reduce the voltage for low cell voltage disconnect. Seems odd.

The BMS may have disabled discharge at 2.5v, its a common low cell voltage shutoff. Maybe the battery can still be charged? There is probably a release voltage that enables the BMS, perhaps 2.8v.

Do you think you can replace that one bad cell? Its looks pretty tightly wrapped. Any idea what the bus bars look like? Spot welded? Bolted?

If you can put a charge on the battery and show that the cells are also wildly different voltages at a higher voltage you could make a good case to return the battery or get it replaced. That and your low voltage numbers from 2.5v, 3.1v and 3.24v.

There is a simplicity of complete battery systems. When they work they are great. When something needs tinkering, its really hard to not only diagnose but often impossible to fix.

If you could bust the battery into individual cells and perform a parallel top balance, you may get them to behave better. And with a better conditioned set of cells, you might find a reasonable working range to get 70-80% (all guesses) capacity from the battery. A better BMS would help too.

 

[dieselenvy]

Yes I can easily break the pack apart. I will look for a charger that will allow me to charge the cells individually. I think that is a good idea, to break the pack down and fully charge each cell individually and install to a new BMS that I can actually get a manual for and program. I purchased this battery from ZL Power in China, they will not respond to any emails involving returns or refunds. I wish I had purchased raw cells and a BMS and to built my own, but that is hindsight and here we are. I think we can salvage the pack. If someone recognizes this BMS and can provide access to a manual so I can understand how it works and how to properly program it, then I could probably use it. But as it is, its basically unusable and just a headache. Will the 48v Overkill BMS work easily with this pack? The pic is half the pack.

 

[MisterSandals]

First thing you should do is label your cells. I recommend using letters (A, B, C...) because when taking notes, the cell position in the battery is a number and notes quickly get undecipherable.
Make notes about anything like where they were (cell position) in packs, voltages, anything you can come back to and maybe learn something.

You have quite a few cells, so you could make 2x 24v batteries that you could charge with solar (you're the bms so charge conservatively) and us a DC-DC charger like this to top balance the other 8 cells in parallel:

Amazon.com: Xiangtat T8 Battgo Lipo Battery Charger/Discharger, Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb : Toys & Games

Amazon.com: Xiangtat T8 Battgo Lipo Battery Charger/Discharger, Balance Charger Discharger 30A 1000W DC 2-8S LCD Display Digital Smart Battery Balance Charger for Li-Po Li-Hv Li-Ion Li-Fe NiMH Ni-Cd Pb : Toys & Games

www.amazon.com

Then when the 8 cells are top balanced to 3.6-3.65v, you assemble that into a 24v battery, charge with solar and top balance the other 8 cells.

This is what i did, completely solar powered. Its quite a nice little charger, perhaps more than i needed since it hasn't been used in about 6 months (last time i assemble a battery). They make ones that are around $65.

I've never owned a bench top charger but I am rather pleased i have this Battgo as it does quite a few other functions and I have quite a few cells (over 40) and battery packs... 4S, 6S, 8S.

Most others use bench top chargers to top balance... a search would yield many many recommendations.

EDIT... realizing your SCC is 48v, probably won't charge 24v. Was decent, well intentioned thought.