I’ll try to help you and others.
- The upgrade versions of C4-12 and C4 have longer slots to load secured 21700 batteries.
- Further the C4 now had an internal power supply. First one had external.
- The C4 Plus has wider slots for suiteable 4 x 26650 batteries, which don’t fits into C4 and C4 upgrade.
- The C4-12 always charges at max. 3A - doesn’t matter how many slots are used. A maximum at 4x 3A = 12A max. Ni-MH at 1A.
- The C4 Plus charges Li-Ion batteries at 2 x 2.5A or 3 x 2.0A or 4 x 1.5A. It also depends how many slots are loaded. Ni-MH at 1A.
- The basic C4 charges Ni-MH at 800mA each slot and discharging only in slot 4, with 400mA. But normally this is a very ols charger and should be sold out.
- The C4 V4 (Release 12/2019) charges Li-Ion batteries 2 x 1.5A or 3 x 1.3A or 4 x 1.0A - depending how many slots are loaded. Discharging only in slot 4, with 400mA max.
- There is also a C4 V3 (Release 11/2019) which is similar with V4, but without discharging option.