As I have mentioned elsewhere in the past, hobby chargers are not the best tool for maintaining individual, or "loose" NiCd/NiMh cells. Li-Ion cells are a different story.
The problem with hobby chargers and nickel based cells, is that multiple cells can usually, only be charged in series. This is a problem that is hard to get around no matter how you go about it. For battery packs that are spot welded together, you don't have much choice but to charge them in series. This is why hobby chargers provide series charging for battery packs used in the R/C hobby. Nonetheless, charging cells in series always runs the risk of unequal charging of cells. As has been mentioned, at a 0.1C rate, this isn't so much of a problem, as this slow rate is less damaging to cells.
I've used the iCharger "forming charge" with welded battery packs, such as the 14.4 and 15.6 Volt packs used in my M@g 623, as well as other "packs". It seems to work well enough, although I agree that it isn't really quite the same as a true forming charge, or a"break-in", as is done with individual cells in a Maha C9000.
I have also used the iCharger "forming charge" to charge 4 "loose" NiMh D cells connected with magnets in series. As long as the cells are well matched and in the same state of charge at the beginning of charge, it will work reasonably well.
The biggest potential problem is likely to occur during the initial CC/CV portion of the charge (charge current is initially at a 1C rate, as you would normally enter the cell's capacity when setting up the charge). Checking the individual cells with a DMM during this phase will reveal that not all cells are at the exact same voltage. Again, if your cells are well matched and start out in the same state of charge, this shouldn't be much of a problem. If however, your cells are not well matched, you run the risk of overcharging one, or more cells during this first CC/CV stage. Once the program drops the current to 0.1C, the risk of overcharge is greatly reduced, as this is the same rate as an actual forming charge. That said, the damage may already be done at this point.
Short of using the iCharger "forming charge", I think the best way to attempt to duplicate a forming charge with a hobby charger, is to simply do a "normal" charge at a 0.1C rate, setting the time limit to 16hrs. Often hobby chargers will miss the -dV termination at this slow rate, and the charge will continue until the 16hr limit is reached. On the other hand, if the -dv does trigger, well, then you're screwed.:sigh:
I'll also add here that I've never had much luck charging single NiCd, or NiMh cells with a hobby charger. I've heard others mention this as well. I don't know what the problem is, but often termination is either too early, or is missed altogether, when charging a single cell. I've adjusted the -dV to no avail, attempting to correct this problem. The -dV termination seems to stand a much better chance of triggering when multiple cells are charged in series. I cannot explain why this is.
It is my opinion that other than for welded battery packs (again, where you have no choice but to charge cells in series), the charging of individual NiCd and NiMh cells, should be relegated to dedicated, independent channel, NiCd/NiMh chargers. Hobby chargers are really only meant for charging battery packs. As I mentioned earlier though, concerning Li-Ion cells, things are a bit different.
Dave
