The way my xtar (6 bays) works is that if you put a pair of batts side-by-side,they will charge at 0.5A but only one per 2 slots its 1A...6 slots,3 pairs,all separate circuits.
Additional spacers required (like a buck each) I got 10 total,all set for 14500,18350,18650,etc (if they are 4.2 fully...