Yep, it´s the VC4 I meant. It´s a very simple charger without any settings but my No.1 for low-voltage NiMH
You need to have a Power Supply for it with USB 5V/2,1A
Stay away from the VC4SL which is unusable as a NiMH-charger and it also show error with low-voltage NiMH
For it´s features the ISDT C4 EVO is cheap IMHO but due the small size, bugs and annoying fan not build for everyone, I use it atm very rarely
right, i read that c4 evo experiences thread and it was very illuminating! O.o If the bugs were worked out, I bet it would be cool w/that replacement case that fits the Noctua fan.
Yep, but not sure how many work ISDT will do on it.
Looks like they´re more the guys for hobby chargers than for round cell chargers
So, the VC4 is AMAZING!!! It charges anything!!! I tested with multiple “C” and “AAA” nimh batteries w/less than 0.5 volts on the MM and it charged every last one.
Now, some C batteries it charged to over 4000+mah (per its’ display) and some to only <100mah, so I guess it doesn’t do much of a ‘recharge’ function here, but now I can try to ‘refresh’ them to see if any storage can be recovered.
I also bought a Vapcell S4+ 3.0 and am hoping that the ‘repair’ option will work similarly to the Opus Discharge/Refresh mode. But, without the Xtar charging ALL of these cells to a sufficient voltage, I would be out of luck to even try this (without connecting a bunch of batteries in serial and putting one the wrong way, bc i have that kind of luck). So, thanks again for that great smart–but not too smart?–charger recommendation!
It´s nice that I could help you 
Overall the VC4 is not the best NiMH-charger, it sometimes make a to early termination; but not to compare with the VC4SL which is much more awful.
I use the VC4 only to give low-voltage-NiMHs a 1st boost, maybe I charge 100-200mAh and then I use the Vapcell S4+ because it terminates problematic, deep discharged NiMHs much better than any other of my many chargers
But still I don´t believe in the refresh/repair-function of chargers. No miracles would happen with it, a worn cell will be not good again. And it takes a lot of time, but maybe OK for ppl who can wait and don´t want to charge/discharge manually every time
I’ve got the Xtar VC8S and have noticed it may “spit the dummy” at low voltage NiMh Eneloops, but if I leave them in the charger (and come back later) they are then charging fine. This usually happens where I’ve used them in night lights in 4S config where one obviously gets flattened more than the others.
Over-discharged NiMHs causes 3 typical problems in my experience
If I know these cells are problematic I use mostly my Vapcell S4+ and don´t leave the charger to long alone