Agree!
I prefer 250mA for NiMh
Probably I can do 500 for the Eneloop Pro
Jep, also my standard setup, as long there are no âSolarâ-NiMHs with very low capacity.
I hope anyone test the VC8S with a lot and critical NiMHs but I doubt that Xtar improved the VC8 a lot
While I agree with you on the âdumbâ chargers bit, they are not what they used to be 20 years ago (trust me, been there, done that, way back to when Nicads were still mainstream for RC stuff and we had to change how we did things when sub-c NiMH came along). They have gotten better at delta-v detection for charge termination. I agree that some do it better, but even the cheap bundled chargers for the Laddas and Eneloops are good. They charge at under 100 mA for the 2450 mAh AA and AAA and this is what the manufacturer recommend for cell life and capacity, especially for the LSD cells. You can go higher than that, and i donât think it would be bad to charge at 500 mA for the 2450 mAh AA, but my 900 mA AAAs get too warm at 250 mA up to 1.5v on the Vapcell S4+ (v2) so I charge them only when necessary.
NiMH charging is complicated. If relying on -dV/dt termination, then moderately high charging currents may produce an easier to detect transition to avoid overcharging. Eneloop even lists the BQ-CC55 as a recommended charger. It charges at up to 0.67C (1.3A).
If relying on time or voltage, lower charge currents reduce the negative effects of overcharging.
The standard charge cycle per IEC 61951-2 for determining capacity is 0.1C (200mA for a standard Eneloop) 16 hours. That is to say, the standard charge is to overcharge by 60%.
Furthermore, the IEC life cycle tests mandates that cycles be accrued at 0.25C, so 500mA is the charge rate used for that 2000 cycle rating. But they never deep discharge them, which is worse for them than overcharging, and probably even than fast charging. Itâs always a 58% discharge cycle, followed by a 79% charge cycle, resulting in a 21% overcharge.
The Eneloop datasheet mentions both the IEC capacity charge cycle (0.1C for 16 hours), and a âfast chargeâ cycle of 1C (2A) for 1.1 hours âusing recommended charging system,â which presumably means a -dV/dt charger.
So per the authoritative source, it is acceptable to use either slow or fast chargers for low self-discharge NiMH batteries, although it is not clear which is optimal for cycle life. We only know that the official rating is based on slow cycles with a moderate overcharge.
Thank you for checking voltage consistency. Thatâs a nice detail not typically done.
I also read your grade mode test for NiMh with interest, because the Xtar VC4SL (aka VC4 Plus) is documented to have problems with consistency in charging NiMH. It doesnât seem clear if it is due to using voltage termination, which is not reliable with NiMH batteries, or some other flaw:
Johnny_Bravo documented NiMH charge cycles ranging from termination at only 25% capacity up to not terminating until pushing 165% of capacity into the battery. Since the VC4SL charges at up to 1A, it is doubtful that the overcharging is benign, and the undercharging would be a nuisance.
Fortunately, your VC8S test showed better consistency at 103% to 109% of capacity.
As more people try out this charger, it will be helpful to the community if they can note if they see inconsistency in NiMH charging like the VC4SL, or if this charger is improved.
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I regret getting a VC8 Plus on 11/11 now⌠anyone want to buy one? 
Looks nice. Do you find it terminates closer to 4.20? My VC8 Plus terminates a little low sometimes with small batteries.
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Yeah, itâs terminating between 4.18-4.20V when I charge good quality 3.7V Li-ion cells.
I noticed it terminate a protected 18350 cell at around 4.139V. But I left it in the charger for another 10 hours while waiting for all the other cells to finish. The quality of the cell, and the slight parasitic drain (1mA) from the VC8S when not charging might have dropped it a bit.
One thing I noticed with the VC8 was that it would consistently terminate early in certain slots. The VC8S seems better. I gave the VC8 away but I probably wonât give this VC8S away.
I noticed this as well, it would be interesting to see a tear-down between the two to see if this is because of differences in wiring, etc.
I would really like to know, for sure, whether that is true.
I would like to buy the new VC8S, but the manual available online states clearly that charging rate for 8 x AA (i.e., 1.2 V cells) is only 0.5A.
It is simply unacceptably slow to charge an AA cell that is >= 2500 mah, at only 0.5 A.
Thank you.
DG
Sorry, thatâs for Li-ion cells.
The VC8S defaults to 0.5A for 1.2V Ni-MH cells and this cannot be adjusted.
Thx. I may get this one to replace VC 4 plus