I know little about chargers. Sofirn offers 4 models here. I’d like to get one to charge Lithium batteries, most likely 18650, 18350, 16340 and possibly 21700. I was hoping that they would charge a bit slower, with lower current than the flashlights’ internal chargers. I noticed that some need USB charger to work (micro or C plug?) and some are more expensive than others. I was hoping for cheap and small, but…
Could I be briefly explained what I should choose and why? Cheers!
Do you need to be able to use a USB supply? Some people like this. I don’t, but it depends on what you need.
That having been said, many seem to like the Vapcell S4 plus. I have one and use it regularly. (When I just want to charge smaller cells at low currents. Otherwise I use my SkyRC MC3000).
Here is a thread on the latest V3 model:
Here is a comprehensive review, It is on the older model, but except for a couple of feature additions on the V3, it still should be accurate:
It covers most of the bases for many users. It can charge as low as 250 mA for LiIon cells and up to 3 amps. It can do capacity testing. It shows Internal Resistance, I believe the V3 also has a storage function (mine is a V2). It will charge LiIon and Nimh cells. A pretty comprehensive feature set.
Cheers! The S4+ is the most expensive one that Sofirn sells. Would that mean that their cheaper models should be avoided for any reason?
I can’t really answer that as I have no experience with any of them. Hopefully people that have used them might comment.
I am guilty of usually getting the most fully featured chargers. I have a couple of the MC3000s which some consider to be too expensive. But I have lots of cells and think that I “need” the flexibility and hopefully, accuracy, that the top of the line chargers offer.
I would not specifically look for a “Sofirn” charger. I would not consider an unbranded charger. I would look for a branded charger that has already been expertly and favourably reviewed, such as the Vapcell S4+
You may want a display of the voltage and the charging current. You may want to manually-select the charging current.
I use my Nitecore UM2 and UMS2 chargers, but I treat them gently. I avoid removing the micro-USB plugs from the micro-USB sockets in the chargers.
Look for two happy faces that do not overlap:
https://lygte-info.dk/info/roundCellChargerIndex%20UK.html
(I use my Olight UC Charger to charge my 26800 cell at 750mA, because the cell is 80mm long).
You will probably also need a multimeter to measure the voltage of the batteries.
My charger of choice is the Vapcell S4+.
I have two of them.
Good luck in your search. 
If you still want a cheap, small, slow, lithium-ion only, charger, consider the Xtar VC2. It charges at 500mA. My Samsung 50E 21700 flat-top unprotected cell will just fit in my VC2. HKJ quoted a maximum of 71mm length for the VC2. He reviewed the VC2 in the year 2014. There were two happy faces then, and they did not overlap:
https://lygte-info.dk/review/Review%20Charger%20Xtar%20VC2%20UK.html
The S4+ is the best value charger imo, just don’t use the powerbank feature.
Yep, that’s excellent advice.
The S4+ works great except for the powerbank feature, which can cause a fire/self-destruction. 
The S4+ is good value for what it does, i wouldn’t describe it as cheap or small though.
Do you need any analysis features? Capacity testing/internal resistance/etc?
What is the lowest current you require? 16340 is smallest cell size on your list, these come in 650-850mAh capacity, so a charger with 500ma output would be good for these to charge at less than 1C. If you really wanted to “slow charge” them, you’d want a charge current of 250ma, but this is overkill…
You don’t mention how many slots you need. For my uses, I look at it as follows:
1 slot chargers are good for travel, 2 slots for travel if you anticipate heavy charging requirements or for a compact home set-up. 4 slots for a “main” home charger, especially if you’ve lights that take 3+ cells.
Bigger chargers (more slots and faster charge rates) have higher power demands than smaller chargers with lower charge rates. The S4+ comes with a powerbrick, be aware of this when you’re looking for a “small” charger. A minority of chargers use a fig-8 cable to plug directly into the mains, eliminating the power stick. The majority of small chargers use USB input. Some still use micro-usb ports…
I’ve not read any reviews, but was actually thinking of picking up a Xtar FC2 Charger to replace my Vapcell U2 because it uses a micro USB socket.
*Not clear whether the two slots have the ability to have different currents.
Reviews suggested that the Xtar FC2 charger had a micro-USB socket. Perhaps only the latest version is USB-C.
Ah yes, quite right, I neglected to mention this important point!
I did not like my vapcell S4+, but I do really like the xtar vc4 plus.
Opposite of me. I’m not a big fan of the Xtar VC4 Plus, but I like the Vapcell S4 Plus V3 that I have. Just got it. Has almost as many features as my SkyRC (which has a broken contact spring on slot two, which is why I stopped using it for the most part) and I love all the data on the screen.
As an aside… have you looked inside of your MC3000? Often the little post that holds the spring breaks. Conveniently there is a hole in the PC board that you can connect the spring to. I have needed up having to do that for all 4 slots on my 12 year old MC3000. It is a pretty easy fix. I think worth doing if this is what is keeping you from using this excellent, and expensive, charger.
Also, I like the S4. I just recommended it to a close friend…as well as here. I use it regularly with small cells because it is super easy to change the charging current. But it simply cannot do even half of what the MC3000 can when it comes to tweaking everything the way you need it to be. Nor is it as accurate (no ability to calibrate). It clearly can be good enough, but not close to the MC3000. But heck, the S4+ V3 costs around one third as much.
I will likely do that. But I also like the S4 for its relative simplicity. One can just toss a battery in and go, more or less, if they don’t have any real specific charging needs they want to meet. Plus, I have other people in the house that use that type of charger and don’t want to fiddle with anything more complex than put the battery in and charge.
There is value in simplicity. But you have the best of both worlds. The simplicity of the S4 and you have an MC3000 for all of the benefits that it brings.