(1) All your BMS can use the high series to low series?
Answer: No, not really. Some mother board can do, some one can't.
(2) What to do if i want to connect 10S to your 13S BMS?
Answer: If the board set the short system,then you can connect the BMS like below.
Contact:Shawn Xiao
Phone: +8613713704256
Email:sales@rjxzstech.com
Add:5D Buliding1,LongHua New District,ShenZhen City, GuangDong Province,China