I’m currently reviewing the XTAR VC8S simply by using it and recording my observations (not as advanced as HKJ’s XTAR VC8 review).
One big upgrade with the VC8S over the VC8 is that you can use all 8 slots now instead of 4 for the Store and Grade modes.
Storage mode will charge or discharge a Li-ion cell to 40% SoC (State-of-Charge). I.e. 3.6V. This can help improve the life of a Li-ion cell when in storage.
Storage mode will discharge a Li-ion cell at a rate of 300mA or discharge it to 3.60V. I found that it terminates around 3.58V to 3.61V.
Storage mode will discharge or charge a Ni-MH cell to 1.2V. I found that it terminates around 1.31V to 1.35V. I noticed that it pretty much always tries to charge the cell for about 10 minutes before discharging.
More info about storing batteries here.
The termination voltages are much better than the VC8 that I previously had.