Short Version: the cells delivered to me by Michael B Caro were Grade B REPT brand. Not Keheng.
EVE LF280K fit nicely as a replacement, and stay in balance just like the REPT cells do.
Longer version:
Two purposes in this post: 1) show where to get replacement cells for the "Keheng Grade A+" from MCB and 2) Mention a very nice write up from Ghostwriter66 about how to determine cell quality.
I haven't found this anywhere else. I discovered something that others who paid MCB for Keheng 280ah cells might want to know. He said: "I get these cells shipped straight from the factory with no supplier/reseller involved at all. They are True A+ cells that are matched and batched in groups of 16 at the factory and come with the factory test report of the actual cells that are shipped to you." September of 2021 (normal 2 months wait), two of my 16 were delivered damaged, and two were lost by UPS. No factory test report (in the missing box?). I top balanced 8 of them, hooked them up 8S, ran a 1100 watt heater for over 7 hours (down to 2.8 volts lowest cell). So the capacity is good. I was happy.
Six months later, still no replacement cells from MBC.
Dealing with MBC, someone elsewhere here said "it's over with, move on". In the process of moving on about a month ago, I saw this from @ghostwritter66:
diysolarforum.com
That should be in the Beginners Resource section. She wrote that 3 weeks before my cells were delivered. I wish I knew enough then to go find it. I hope that resource helps someone else.
I found a lot of scratched off QR codes underneath the black plastic top cover, between the negative post and the outside of the cell. Except for one.
https://www.gobelpower.com/lifepo4_decoder.html using 08LCB26001179A9BF0100803 shows they are REPT brand 280AH cells, made in late 2019. Not what I was expecting.
There are a lot of great minds on this forum. One of them posted this:
diysolarforum.com
Thanks @RayfromTX.
Jenny Wu came up with Eve LF280K cells. I contacted her thru gmail, then Alibaba. I needed 4 cells to replace the two damaged and two lost cells. Her boss was reluctant to sell me a different brand than what I had. Eventually, she came up with sending me just one, for me to test. It showed up in about a week. The two cell brands are physically the same width and depth, but Eve is taller and has wider terminal post spacing. However, the Eve terminal post landings are closer to the cell. The two brands of cell terminals end up the same height. Nice. I had to re-think bus bars because of the different terminal spacing. I/R was the same (0.17 to 0.19 mOhm measured with YR1035+ - yellow box). I discharged to 50%, uncompressed the pack, randomly pulled a cell out of the 8S pack I had, replaced it with the new EVE cell, then re-compressed. I charged that one cell to the same voltage as the other 7 with a 10 amp lab power supply (Thanks Will). Then fully charged using the inverter. I then ran the same 7 hour discharge test - 1100 watt heater. Electrodacus SBMS0 default voltages are between 3.55 and 2.80 per cell. The bms turns off the charger when any cell is at or below 2.80 volts for at least 3 secs. Full is 3.55 volts for more than 6 seconds. That test came out to 7 kwh, the same as before. Typical resting delta is 4-8 mv. Yea. I ordered the other 3 cells I need to make my 2P8S 560 aH 24 volt battery. I used the one cell I pulled out, plus 3 new Eve cells, plus 4 REPT cells I never used before. Turned on the charger to get close to a top balance. One cell was a lot higher voltage than the others. I ended up charging each one individually within the same 8S pack. I could have drained the high one, but I knew how to charge one at a time.
After all that, another 7 hour test with the same heater, the two 8S 24 volt packs were within 32 watt hours of the same (usable to me) 7Kwh capacity. Nice.
I am going to use this method (PCCB) to build the actual 2P8S battery that will go in our RV.
diysolarforum.com
Thanks @Posplayr.
More on the actual build later.
EVE LF280K fit nicely as a replacement, and stay in balance just like the REPT cells do.
Longer version:
Two purposes in this post: 1) show where to get replacement cells for the "Keheng Grade A+" from MCB and 2) Mention a very nice write up from Ghostwriter66 about how to determine cell quality.
I haven't found this anywhere else. I discovered something that others who paid MCB for Keheng 280ah cells might want to know. He said: "I get these cells shipped straight from the factory with no supplier/reseller involved at all. They are True A+ cells that are matched and batched in groups of 16 at the factory and come with the factory test report of the actual cells that are shipped to you." September of 2021 (normal 2 months wait), two of my 16 were delivered damaged, and two were lost by UPS. No factory test report (in the missing box?). I top balanced 8 of them, hooked them up 8S, ran a 1100 watt heater for over 7 hours (down to 2.8 volts lowest cell). So the capacity is good. I was happy.
Six months later, still no replacement cells from MBC.
Dealing with MBC, someone elsewhere here said "it's over with, move on". In the process of moving on about a month ago, I saw this from @ghostwritter66:
How to tell the difference between Grade A and Grade B cells.
How to tell the difference between Grade A and Grade B cells. AND why you should always pay with CREDIT CARD. Going to make this sort of in bullet form – otherwise this will go on for many of pages of rambling which this will probably be anyway.. Before I start …25C is 77F – the perfect...
diysolarforum.com
That should be in the Beginners Resource section. She wrote that 3 weeks before my cells were delivered. I wish I knew enough then to go find it. I hope that resource helps someone else.
I found a lot of scratched off QR codes underneath the black plastic top cover, between the negative post and the outside of the cell. Except for one.
https://www.gobelpower.com/lifepo4_decoder.html using 08LCB26001179A9BF0100803 shows they are REPT brand 280AH cells, made in late 2019. Not what I was expecting.
There are a lot of great minds on this forum. One of them posted this:
Our NEW GO-TO LiFePO4 vendor...09.20.21
So my boss this morning stopped by the DONCAN warehouse (Doncan Technology (Shenzhen) Co) in Houston TEXAS to pick up (64) EVE-280Ah batteries that we had ordered literally 48 hours earlier. From beginning to end this has been a 10 out of 10 process. First it started with Jenny Wu of Doncan...
diysolarforum.com
Thanks @RayfromTX.
Jenny Wu came up with Eve LF280K cells. I contacted her thru gmail, then Alibaba. I needed 4 cells to replace the two damaged and two lost cells. Her boss was reluctant to sell me a different brand than what I had. Eventually, she came up with sending me just one, for me to test. It showed up in about a week. The two cell brands are physically the same width and depth, but Eve is taller and has wider terminal post spacing. However, the Eve terminal post landings are closer to the cell. The two brands of cell terminals end up the same height. Nice. I had to re-think bus bars because of the different terminal spacing. I/R was the same (0.17 to 0.19 mOhm measured with YR1035+ - yellow box). I discharged to 50%, uncompressed the pack, randomly pulled a cell out of the 8S pack I had, replaced it with the new EVE cell, then re-compressed. I charged that one cell to the same voltage as the other 7 with a 10 amp lab power supply (Thanks Will). Then fully charged using the inverter. I then ran the same 7 hour discharge test - 1100 watt heater. Electrodacus SBMS0 default voltages are between 3.55 and 2.80 per cell. The bms turns off the charger when any cell is at or below 2.80 volts for at least 3 secs. Full is 3.55 volts for more than 6 seconds. That test came out to 7 kwh, the same as before. Typical resting delta is 4-8 mv. Yea. I ordered the other 3 cells I need to make my 2P8S 560 aH 24 volt battery. I used the one cell I pulled out, plus 3 new Eve cells, plus 4 REPT cells I never used before. Turned on the charger to get close to a top balance. One cell was a lot higher voltage than the others. I ended up charging each one individually within the same 8S pack. I could have drained the high one, but I knew how to charge one at a time.
After all that, another 7 hour test with the same heater, the two 8S 24 volt packs were within 32 watt hours of the same (usable to me) 7Kwh capacity. Nice.
I am going to use this method (PCCB) to build the actual 2P8S battery that will go in our RV.
Parallel Cell Capacity Balancing (PCCB) Procedure.
INTRODUCTION I’m going to describe my setup and the initial electrical performance results as well as a balancing technique that I think is pretty effective at matching parallel cells (e.g an 8 cell 4S battery or a 16 cell 8S battery). I’m a semi-retired Electrical Engineer, but this is my...
diysolarforum.com
Thanks @Posplayr.
More on the actual build later.
