Experience sharing - Buying a 51.2v 14.33KWH Wall mount battery pack from Shenzhen Basen Tech (US stock)

[mvreddy48]

This is the status at almost full charge.

 

[Boognevatz]

Hey, I also bought a Basengreen wall mountable (also has wheels) battery pack with integrated BMS, the 14.3kWh version (16s, 280Ah, 51.2V).

I connected with the inverter using "pylontech" protocol, the inverter is MPPSolar u5648. Everything seems communicating nicely (the inverter disables output if battery goes under 14%, it displays the battery percentage (25,50,75,100%). If I disconnect the communication cable the inverter starts beeping and flashing red.).

The battery is in use one month, and the capacity is almost halved. So it is about 8kWh.
I worry it will decline even more. How can I counteract its premature aging?

 

[Supervstech]

Hey, I also bought a Basengreen wall mountable (also has wheels) battery pack with integrated BMS, the 14.3kWh version (16s, 280Ah, 51.2V).

I connected with the inverter using "pylontech" protocol, the inverter is MPPSolar u5648. Everything seems communicating nicely (the inverter disables output if battery goes under 14%, it displays the battery percentage (25,50,75,100%). If I disconnect the communication cable the inverter starts beeping and flashing red.).

The battery is in use one month, and the capacity is almost halved. So it is about 8kWh.
I worry it will decline even more. How can I counteract its premature aging?

What is the fully charged voltage?

 

[Boognevatz]

What is the fully charged voltage?

SOC 14%

cell01 3271
cell02 3273
cell03 3271
cell04 3273

cell05 3271
cell06 3273
cell07 3271
cell08 3272

cell09 3271
cell10 3272
cell11 3274
cell12 3274

cell13 3275
cell14 3273
cell15 3272
cell16 3276

Mind you, it hardly goes to 100% these days, it displays 99% at the display.

SOC 99%
cell01 3352
cell02 3411
cell03 3379
cell04 3417

cell05 3414
cell06 3350
cell07 3392
cell08 3431

cell09 3434
cell10 3360
cell11 3367
cell12 3435

cell13 3399
cell14 3364
cell15 3470
cell16 3469

 

[wpns]

You probably need to get it to 100% and hold it there while it balances out.

 

[42OhmsPA]

SOC 14%

cell01 3271
cell02 3273
cell03 3271
cell04 3273

cell05 3271
cell06 3273
cell07 3271
cell08 3272

cell09 3271
cell10 3272
cell11 3274
cell12 3274

cell13 3275
cell14 3273
cell15 3272
cell16 3276

Mind you, it hardly goes to 100% these days, it displays 99% at the display.

SOC 99%
cell01 3352
cell02 3411
cell03 3379
cell04 3417

cell05 3414
cell06 3350
cell07 3392
cell08 3431

cell09 3434
cell10 3360
cell11 3367
cell12 3435

cell13 3399
cell14 3364
cell15 3470
cell16 3469

The balance is pretty terrible.
Recommend disconnecting all communications, setting the battery to user with a bulk/boost of 56V and float at 55.2V for a few days. If you get high cell disconnects reduce bulk in small increments. You'll need to keep an eye on them as they get close to 55V.

 

[Boognevatz]

Recommend disconnecting all communications, setting the battery to user with a bulk/boost of 56V and float at 55.2V for a few days.

Thank you very much for the suggestion, also sorry for the late reply; october and early november was quite sunny here (24-28kWh/day), so did not wanted waste a day for battery balancing.

But now the weather is pretty bad (4-6kWh/day), so I played with it. I started with 98% state of charge, and I switched off the solar, and I gave utility power to the solar inverter.
I set 10A charging (572W), 55.2 floating voltage (16x3.45), and 56V for the boost voltage.
From 98% to 100% it charged 5.1kWh into the battery, on the solar inverter the charging current was 9A, on the battery it show anywhere from 8.9 to 9.3A.
At 100%, there is no charging current (displays 0A), the floating voltage is 55.2V, it was at noon (today).
I wrote down each cell voltage (from the battery display) at 12.00, 15.30, 16.30 and 18.30. (right now it is 19.05)
Here it is:

   12.00 15.30 16.30 18.30  21.50

 1  3407  3382  3375  3372  3370
 2  3445  3456  3458  3455  3450
 3  3447  3433  3424  3418  3414
 4  3461  3474  3475  3475  3474
 5  3468  3471  3473  3474  3474
 6  3399  3376  3367  3366  3364
 7  3460  3448  3439  3435  3434
 8  3478  3486  3489  3490  3491
 9  3477  3487  3488  3490  3490
10  3417  3399  3395  3396  3395
11  3427  3411  3406  3404  3404
12  3466  3479  3480  3474  3467
13  3468  3466  3464  3462  3460
14  3418  3405  3402  3404  3404
15  3495  3529  3549  3557  3565
16  3494  3529  3547  3557  3565

It seems like instead of balancing the cells, it gets even worse over time (cell15 and cell 16 especially).

Edit:
Just updated the table with 21h50 results and I also stopped the experience (switched off utility), because the last two cells starting to really go out of balance.
I do not know what exactly does this BMS if any.

 

[No-one-&-Not-Important]

Thank you very much for the suggestion, also sorry for the late reply; october and early november was quite sunny here (24-28kWh/day), so did not wanted waste a day for battery balancing.

But now the weather is pretty bad (4-6kWh/day), so I played with it. I started with 98% state of charge, and I switched off the solar, and I gave utility power to the solar inverter.
I set 10A charging (572W), 55.2 floating voltage (16x3.45), and 56V for the boost voltage.
From 98% to 100% it charged 5.1kWh into the battery, on the solar inverter the charging current was 9A, on the battery it show anywhere from 8.9 to 9.3A.
At 100%, there is no charging current (displays 0A), the floating voltage is 55.2V, it was at noon (today).
I wrote down each cell voltage (from the battery display) at 12.00, 15.30, 16.30 and 18.30. (right now it is 19.05)
Here it is:

   12.00 15.30 16.30 18.30  21.50

 1  3407  3382  3375  3372  3370
 2  3445  3456  3458  3455  3450
 3  3447  3433  3424  3418  3414
 4  3461  3474  3475  3475  3474
 5  3468  3471  3473  3474  3474
 6  3399  3376  3367  3366  3364
 7  3460  3448  3439  3435  3434
 8  3478  3486  3489  3490  3491
 9  3477  3487  3488  3490  3490
10  3417  3399  3395  3396  3395
11  3427  3411  3406  3404  3404
12  3466  3479  3480  3474  3467
13  3468  3466  3464  3462  3460
14  3418  3405  3402  3404  3404
15  3495  3529  3549  3557  3565
16  3494  3529  3547  3557  3565

It seems like instead of balancing the cells, it gets even worse over time (cell15 and cell 16 especially).

Edit:
Just updated the table with 21h50 results and I also stopped the experience (switched off utility), because the last two cells starting to really go out of balance.
I do not know what exactly does this BMS if any.

Maybe check this video (19m-30m) & this video?

From these videos, I recommend you open your case and check a few things:
1. Check BMS settings are correct for your cells, e.g.: high BMS charging rates or cold charging can worsen this.
2. Check BMS settings against raw values tested on the cells themselves? The BMS may be struggling to balance cells during charge cycles, especially near full charge, as shown in the second video.
3. Check if the cells in your case are wired up (busbars are the same, wires are the same, etc...) to enable balanced charging? Sometimes wire lengths or the materials use can cause imbalanced charging even if the BMS is setup properly, because the path resistance to each cell isn't the same) and the cell wiring causes the imbalance?
4. Finally, if all of this checks out, test your cells. It's an arduous process but it can help determine that the cells are/are NOT the problem.

If I had to guess, I'd guess #3 is the problem if the BMS settings check out.

Note: Tests for voltage sag/droop (as per the first video) only "fail" (i.e.: fall to <=2.5V quickly) when cells are nearing EOL. If cells are relatively new (1–2 years) and not heavily cycled, cell issues aren't going to show up. I wouldn't worry about aging as much unless you cycle hard (i.e.: often or during cold conditions), or your cells were near EOL to begin with.

May I learn from your experience? Questions:

• I’m spec’ing my case with a JK-PB2A16S-20P BMS. I’m purchasing cells too (details for later). What BMS is in your case?
• When buying from Basen, did you verify both QR codes (visible top code + the one under the black overlay)?

Re: cells
Manufacturing has variability; some cells "fall out" of spec. I'm in semiconductors (memory cells); "fallout" = Cells that can't meet operating conditions fit for warranty. Instead, we sell them to distributors for other apps (that don't require heavy cycling or harsh operating conditions). Invariably, some distributors falsely advertise these for high-cycle applications. Problems usually show up after 6–12 months. Testing only helps to tell you the cells have gone bad already, i.e.: it's not the BMS.

Hope this helps.

 

[No-one-&-Not-Important]

Maybe check this video (19m-30m) & this video?

From these videos, I recommend you open your case and check a few things:
1. Check BMS settings are correct for your cells, e.g.: high BMS charging rates or cold charging can worsen this.
2. Check BMS settings against raw values tested on the cells themselves? The BMS may be struggling to balance cells during charge cycles, especially near full charge, as shown in the second video.
3. Check if the cells in your case are wired up (busbars are the same, wires are the same, etc...) to enable balanced charging? Sometimes wire lengths or the materials use can cause imbalanced charging even if the BMS is setup properly, because the path resistance to each cell isn't the same) and the cell wiring causes the imbalance?
4. Finally, if all of this checks out, test your cells. It's an arduous process but it can help determine that the cells are/are NOT the problem.

If I had to guess, I'd guess #3 is the problem if the BMS settings check out.

Note: Tests for voltage sag/droop (as per the first video) only "fail" (i.e.: fall to <=2.5V quickly) when cells are nearing EOL. If cells are relatively new (1–2 years) and not heavily cycled, cell issues aren't going to show up. I wouldn't worry about aging as much unless you cycle hard (i.e.: often or during cold conditions), or your cells were near EOL to begin with.

May I learn from your experience? Questions:

• I’m spec’ing my case with a JK-PB2A16S-20P BMS. I’m purchasing cells too (details for later). What BMS is in your case?
• When buying from Basen, did you verify both QR codes (visible top code + the one under the black overlay)?

Re: cells
Manufacturing has variability; some cells "fall out" of spec. I'm in semiconductors (memory cells); "fallout" = Cells that can't meet operating conditions fit for warranty. Instead, we sell them to distributors for other apps (that don't require heavy cycling or harsh operating conditions). Invariably, some distributors falsely advertise these for high-cycle applications. Problems usually show up after 6–12 months. Testing only helps to tell you the cells have gone bad already, i.e.: it's not the BMS.

Hope this helps.

One more thing I forgot to mention (I was updating my spec document earlier this morning), if the internal resistance of a cell is say 1mΩ when it should be <0.25mΩ when it's new, this slight resistance increase may seem like nothing, but it's an indication your anode/cathode deposition is sub-optimal and the cell lifetime cycles is already 10-20% off. If the resistance is higher then this means your cell's life has been shortened even more. This can happen due to deep discharge or discharge during very hot or very cold conditions.

With two stages to consider, the state of the battery when you bought it and 2) how you managed the battery after you deployed it, here are some considerations for you

1. State of the battery when purchased: Of course, you may not know this and it's likely not possible for you to go back and find out now (distributor didn't test, simply won't tell you or they'll lie anyway, e.g.: they may have stored the cell in very cold conditions or they charged it at 1C to get it to 25% SOC to get it out of the factory to you as quickly as possible when you placed the order). But in the future if you choose to purchase, I recommend following this procedure before they ship to you

• Check Internal Resistance: A Live measurement (preferably via recorded video where they show the QR codes they're sending you) measurement of internal resistance of all cells. Pick ones which have resistance as close to <0.25mΩ as possible.
• QR Code Verification
  
  • Send photos of all QR codes for all cells before shipment
  • Show FIRST (Large) QR code through black felt/overlay window
  • Confirm that the cells have SECOND (smaller) QR code hidden underneath the black felt/overlay (original QR code from manufacturer).
• Test Reports: Provide official test reports from the manufacturer with page details visible including official signatories.
• [Optional] (This only applies IF CASE PRE-ASSEMBLY is agreed upon) Case Assembly Video: Send video before shipment of case assembly. Installed cell QR Codes must be shown in video.

2. Managing the battery since you got it: There's a reason why shorter distance EVs use LiFePO4 (not LiNMC or LICoO2) & disallow rapid charging more than a few times per month for warranty purposes. Longer range EVs use LiNMC/LiCO2 cells and can charge much faster with less degradation, but have fewer lifetime cycles. That's because the latter deal with cold and faster charge/discharge much better. So if you're using LiFePO4 cells, then consider how you're storing them and whether or not they're environmentally cooled. Teslas batteries are actively cooled when in operation during hot conditions and actively heated during deep cold weather. And you may want to stay away from deep discharge (i.e.: <20%). Oh, you also don't want to charge to 100% too often. BMS can be scheduled to stay within a specific range and then occasionally go to 100% to "rebalance" all cells. BTW, "rebalance" is a misnomer. Most folks look at rebalancing as the idea that all voltage must be the same. The goal of rebalancing is to measure the cell's parameters to decide which cells to slightly more from so that you don't end up with one badly drawn cell over others and then simply lose your total voltage (which is the most important thing coming out of a multi-cell system).

Hope this helps. If not clear, please let me know how else I can help.