I use the 3 FMA 10XP and charge either as 2 5S or one 10S on each one and Love it. It take 30-45 min from 20% to 100% charge. And in 2-3 hours I can charge enough batteries to fly most the day at the field

I tried a parallel board and I could do more batteries at one time, however I have had cells go bad on me in flight and so now I am anal about getting the IR for each cell, so I can monitor battery performance and check for cells going bad.