Thanks for the questions, providing more info here, the original post is located towards the bottom of this edit. FYI, I did a pretty extensive mechanical design for compression and will have them fit within the front part of a Jayco 28BHS trailer -- making them fit in the tight space was the more challenging part. I haven't yet created the final weather enclosure portion and mounting for the BMS. I plan to share that with the community when I am finished. And, will share the design of the brackets, etc. if someone is interested in building this.
I am using the BMS to judge current draw, I have a Daly BMS 250A, am including a picture below. I did an initial top balance using a 3.65V DC power supply across all 8 cells with all batteries in a parallel configuration. I then reconnected them in a parallel series configuration with 2x in parallel and 4x in series to achieve ~12.8V. I have included a picture of the configuration, as I am lacking words to describe it better than that.
Test #1 - connected roughly 200A load. Of the 8 cells, the 3rd pair of cells ran low <2.5V at ~20% SOC according to the BMS. I found that if I decreased the load to 100A (and then 20A) the battery voltage wouldn't dip and was able to extract a couple more percent usage. I have the BMS set to 560Ah total capacity for the batteries.
Test #2 - Even though I had originally top balanced everything, I wanted to make sure the weaker cells were fully charged. So, I took the 4 weakest cells and charged those separately using my 12V charger. I also retightened all of the screws in the battery in an attempt to make this re-test pass. I redid the test using 200A load, and the same pair of batteries, the 3rd pair of cells dipped below 2.5V at a 222A load; the BMS said it had ~23.2% SoC left when this happened. This time I did not lighten the load, so I was not able to go all the way down to 20% SOC. I judge this re-test as yielding identical results to the first test ... I was hoping that the first test was a fluke, but it seems to have repeated with no deviation.
As far as which cells have the highest voltage, I did not pay attention to that prior to Test #1. I believe prior to test #2 that the 3rd pair had the highest voltage prior to the test (the same pair that runs out of energy/voltage early). I just recharged the batteries, and it does appear that the 3rd pair does indeed has the highest voltage. The voltages are 3.378V, 3.378V, 3.436V, and 3.372V.
I have thought about mixing the first set of 4 that I ordered with the last set of 4 that I ordered. As I had mentioned the last set of 4 have the terminals closer together, and two of them appear to be performing worse. The other two from the last order appear to start drooping towards the end of the test as well, but not nearly as bad. If I mixed those with the first set of 4, my thought is that over-all the first 4 would help compensate and I might be able to get closer to the full 560Ah. Honestly, I would be happy getting 85-90% what was advertised since these are grade B cells, as long as that doesn't mean they are on their way out and will only last year or two. It gets a bit disappointing when the result is close to 75% since it is only 1.5x better than what just a single set of 4 of these would provide.
... original post below :
I ordered two separate orders of four of these https://www.aliexpress.com/item/1005001563505796.html?spm=a2g0s.12269583.0.0.2a277a29mrdHnZ
These were from the link provided under the resource tab. Is it possible to get some encouragement from the moderator regarding this since I ordered them through the link he provided ?
I am using them in a 4x2 configuration for 12V application. I would expect ~560Ah since I am using them in a parallel configuration. The second set that I ordered visually looks different than the first set. The terminals are closer together and the battery is a small amount shorter.
I balanced them and charged them. When I run them at 222A load, which is actually <0.5C since they are in parallel, one of the pairs of batteries goes low voltage (<2.5V) when the battery controller says their should be 23.2% SOC. Both of the pairs from the second set of four I ordered run at lower voltage, but this same pair goes <2.5V on a repeated capacity test.
I am not too happy about this, since I am really only getting around 1.5x what I would should theoretically get from just a single set of 4 batteries. I filed a dispute on Alibaba asking for a refund on my second order. The seller very quickly rejected and now it is going into dispute resolution with Alibaba. I have a feeling they will side with the seller since I read that they usually do.
Any thoughts or suggestions on what I can / should do regarding this ??? What about asking to ship the batteries back to get a refund? Has anyone done that, what is the cost, and is it worth it. Any help / suggestions appreciated !
I am using the BMS to judge current draw, I have a Daly BMS 250A, am including a picture below. I did an initial top balance using a 3.65V DC power supply across all 8 cells with all batteries in a parallel configuration. I then reconnected them in a parallel series configuration with 2x in parallel and 4x in series to achieve ~12.8V. I have included a picture of the configuration, as I am lacking words to describe it better than that.
Test #1 - connected roughly 200A load. Of the 8 cells, the 3rd pair of cells ran low <2.5V at ~20% SOC according to the BMS. I found that if I decreased the load to 100A (and then 20A) the battery voltage wouldn't dip and was able to extract a couple more percent usage. I have the BMS set to 560Ah total capacity for the batteries.
Test #2 - Even though I had originally top balanced everything, I wanted to make sure the weaker cells were fully charged. So, I took the 4 weakest cells and charged those separately using my 12V charger. I also retightened all of the screws in the battery in an attempt to make this re-test pass. I redid the test using 200A load, and the same pair of batteries, the 3rd pair of cells dipped below 2.5V at a 222A load; the BMS said it had ~23.2% SoC left when this happened. This time I did not lighten the load, so I was not able to go all the way down to 20% SOC. I judge this re-test as yielding identical results to the first test ... I was hoping that the first test was a fluke, but it seems to have repeated with no deviation.
As far as which cells have the highest voltage, I did not pay attention to that prior to Test #1. I believe prior to test #2 that the 3rd pair had the highest voltage prior to the test (the same pair that runs out of energy/voltage early). I just recharged the batteries, and it does appear that the 3rd pair does indeed has the highest voltage. The voltages are 3.378V, 3.378V, 3.436V, and 3.372V.
I have thought about mixing the first set of 4 that I ordered with the last set of 4 that I ordered. As I had mentioned the last set of 4 have the terminals closer together, and two of them appear to be performing worse. The other two from the last order appear to start drooping towards the end of the test as well, but not nearly as bad. If I mixed those with the first set of 4, my thought is that over-all the first 4 would help compensate and I might be able to get closer to the full 560Ah. Honestly, I would be happy getting 85-90% what was advertised since these are grade B cells, as long as that doesn't mean they are on their way out and will only last year or two. It gets a bit disappointing when the result is close to 75% since it is only 1.5x better than what just a single set of 4 of these would provide.
... original post below :
I ordered two separate orders of four of these https://www.aliexpress.com/item/1005001563505796.html?spm=a2g0s.12269583.0.0.2a277a29mrdHnZ
These were from the link provided under the resource tab. Is it possible to get some encouragement from the moderator regarding this since I ordered them through the link he provided ?
I am using them in a 4x2 configuration for 12V application. I would expect ~560Ah since I am using them in a parallel configuration. The second set that I ordered visually looks different than the first set. The terminals are closer together and the battery is a small amount shorter.
I balanced them and charged them. When I run them at 222A load, which is actually <0.5C since they are in parallel, one of the pairs of batteries goes low voltage (<2.5V) when the battery controller says their should be 23.2% SOC. Both of the pairs from the second set of four I ordered run at lower voltage, but this same pair goes <2.5V on a repeated capacity test.
I am not too happy about this, since I am really only getting around 1.5x what I would should theoretically get from just a single set of 4 batteries. I filed a dispute on Alibaba asking for a refund on my second order. The seller very quickly rejected and now it is going into dispute resolution with Alibaba. I have a feeling they will side with the seller since I read that they usually do.
Any thoughts or suggestions on what I can / should do regarding this ??? What about asking to ship the batteries back to get a refund? Has anyone done that, what is the cost, and is it worth it. Any help / suggestions appreciated !
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