The chargers with USB connectors don't use them to charge external batteries. They couldn't. There's no way for them to know what size or type of battery is at the end of the cable. The USB is used to power external devices. It turns the charger into a battery bank. Put 4 18860's into a charger, plug a usb cable between the charger and your tablet, and you've got a portable source of extra juice. The charger isn't powered in this scenario.
Thanks for the info. That’s too bad, that kind of feature could have been useful to test or refresh external battery packs.
Just ordered one with the awesome markdown price!
I suppose regarding the fan issue I'll just have to open it up and put a dab of superlube or silicone grease. My old laptop fan requires this maintenance every year and it really makes the noise and vibration completely go away, or at the very least make it unnoticeable.
For what it's worth, the apparent chance of this charger undercharging (based on input here) IMO is a good thing, less stress on cells especially aging laptop pulls.
My main reason for getting this charger is the discharge function to check capacity of all my laptop pulls, and future laptop pulls. I already own a C9000 for NiMH cells and I'm spoiled by the functions it provides. Plus I paid double the price for it compared to what I paid for this charger so it is well worth it at this price point.
Hi!
i have a Problem with my 2.0 Version:
it reads around 0,08 V too low
which results in charging my cells up to 4,3 Volt !!!
does anyone know that behaviour?
Is it possible to discharge to the recommended storage level and hold cells at that voltage?
I pulled mine apart and lubed up the fan just as you said and its been really quiet for a couple weeks now,hope it stays that way for a while 
What do you lube up the fan with, if I may ask. Thanks!
I just used what I had on hand,motor oil with a syringe to get right in there.
Many thanks. I have an Opus 3100 on order and I may need to lubricate the fan soon, from what I read here.
Does anyone know the differences between v2.1 and 2.2 of this charger?
There is a v3.1 version now.
John.
I’ve seen C3400 v3.1. I haven’t seen C3100 v3.1. Who sells it? What are the differences?
V3.1 only discharges li-ion cells down to 3.1v when v2.2 discharges li-ion down to 2.8v
The reason for this change is that low voltage protection on (protected) li-ion cells is set at 2.8v and if this cuts in before the charge finishes the display will show NUFF and you will loose all your data.
The problem is a lot of li-ion capacity`s in data sheets are from discharging to 2.8v and if you only discharge to 3.1v a lower capacity will show.
EDIT: The C3100 and C3400 are supposedly the same, the C3400 might have been made for a certain seller.
John.
It is not, usual the protection will be somewhere between 2.0V and 2.5V.
The change on the 3300 is because it pulses discharge and these pulses may trigger the low voltage protection, even when the battery voltage is above 2.8V with no current drawn.
Well you learn something new everyday.
Thanks Henrik
John.
I would like to know this also.
Edit: found out by myself
I got one on order v2.2 but didn’t realize it’s pulse charging 2A. Would it “hurt” my 14500 cells 800mAh (ptotected)? I’m thinking of canceling my order.
Yeah, I’m in the same boat. I already have a Lii-500 which does not use pulse charging, so I may just stick with it and cancel my C3100 order.
On a side note, I don’t know how commercial Li-Ion batteries differ from consumer grade ones, but this study seems to suggest that pulse charging is actually a good thing:
http://www.sciencedirect.com/science/article/pii/S0378775301008205
Pulse charging is not the same as the pwm regulation BT-C3100/3300 uses.
Thanks!
Do we know what the long term effects are of using PWM regulation charging on Li-Ion cells?
I have not seen any results about that, but I know that small cells are charged with up to 10 times their rating in the pulses.