GeorgeP7

I have noticed a number of 2nd life batteries on the market. Blue Carbon, the very large blue and white case, 24 and 51.2v, are recycled EV automotive BYD cells. The cells are very large and would appear to be high current but marketed at 150AH. The problem comes when the battery fails and backup service is not forthcoming because the retailer wont contact the Chinese manufacturer. The failure tends to be the BMS not the cells. Easy to fix in this case. If your cells are larger than the stated battery pack size and repurposed then you are fortunate as they should last many years. That's assuming the repurposer did their due diligence when measuring the state of health of the cell.

Here are the data sheets for the Thunder Sky Winston battery internal to the Blue Nova. Thunder Winston Cell 130AH.pdf Thunder Winston Cell 60AH.pdf

Thanks for your input. Let me include the photos of the cells in the two different packs i have been involved with. I was called by a customer complaining about the state of charge on his Blue Nova. On investigation of the four year old battery i found a few things that did not add up. The data plates of the customers two batteries are the same but the internal structure is different as you can see from the photos attached. I am getting the data sheets for the cells from the manufacturer later today. Will post what info i get.

May I ask what the 154 means on the data plate of this battery. When i opened it up i found 30AH cells in pairs on one model and 130AH single cells in the other. The manufacturers data sheet for these cells shows a capacity below that suggested of 8 kilowatts. Has anyone else observed this anomaly?

Thanks for the response. What you have said agrees with the situation at hand. From my understanding the RS 232 port on the Mecer cannot be used as a comm line for the Dyness RS 485 port as the two standards are different on this very generic inverter. None the less the unwitting installer has connected the two ports up for reasons best known to himself. The connection may or may not be causing the alarm but it would seem to me the best approach would be to disconnect the lines thus leaving the units as stand alone which may solve the short term problem. But what are the long term problems of not have this connection? I fear the batteries could overheat! As a rule of thumb i believe the inverter and lithium batteries should match each other with a CAN/RS 485 port as a basic safety issue; am i correct in this?

Please could someone let me know what is the purpose of the RS 485 cable between the Mecer Inverter and Dyness 4874? What info flows on this line. Is this just to monitor the battery via the inverter or to control charge rates, voltages, temps etc. Help needed. Regards George