Mixing Pylontech US3000C and US3000B batteries in the same system
I was able to successfully upgrade an existing system that used 4 older US3000C batteries together with 6 new US3000(B) batteries. (Total of 10 batteries)
The first two batteries, including the master, were US3000C, then the next 6 batteries were US3000(B), and the last 2 batteries were US3000C. 
Note it didn’t work when we tested the first 4 US3000C batteries and the last 6 batteries US3000B. The last two batteries (9th & 10th) must be US3000C.