Having bought 2 of these and having faults with both I would not recommend buying one. It charges at a high rate but overheated two of my batteries to burning point. The safety overheating feature did not work. The other one overcharged the batteries cutting down the future usefulness of the battery. Better off with an EFEST slim k2. 2amp charging cheaper and no problems.
The sc4 has a much nicer display.
I literally have no idea what this thing is doing.
Get the sc4 and don't waste your time looking at any of the i series, the i4 I got died within a week and when it did work it was super slow.
The SC4 is by far the best I've tried and the sc2 looks on paper like it should be the same but it's no where near.