XTAR VC4S universal battery charger

[Bud]

Got this one from Amazon for USD $32 to sort through my batteries junk box. I have 2-3 dozens of Li-Ion 18650 from laptop battery packs and another couple dozens of Ni-MH rechargeables. This gizmo caught my eye since it promised to auto-identify and charge all sort of batteries and you can charge different size or storage technology batteries together, with constant current and auto cut-off. The specs also claim over-current, over-charge, over-voltage and short-circuit protection and soft-start function.

Pictures of the box and specification are attached to this post.

The charger has 4 spring loaded battery slots, so you can charge batteries of different physical dimensions. The negative spring loaded contacts though for conducting current rely on rubbing against the stationary slotted metal guides that are soldered to the charger board. Details can be seen in the photos. So maintaining good contact may become an  issue as the metal parts will oxidize with time. For now it worked fine.
Also, because the device is intended for handling all sort or batteries of different diameters, smaller cells like AAA and AA sizes tend to skew in the cavities because there is nothing that would hold them aligned straight between the positive and negative terminals, so some care need  to be taken when putting batteries in to make sure they maintain contact with the terminals.



Here I am charging a Li-Ion and a Ni-MH cells at the same time.



The display is somewhat innovative in its gauge style design. The digital part of the display can switch between current, capacity and internal resistance indication using a button. The other button switches device modes between charging, storage and grading (charging-discharging-fully charging). Here is a close-up of the display:



The device requires external power source (not included) via a Micro-USB connector, and is QC (quick charge) 3.0 compatible, can use either a regular 5V USB source or 9V. Max charging current depends on the type and number of cells being charged.

Now, after a few days of using it literally non-stop, there were some inconsistencies and failures that I experienced with it. On one occasion after a few hours of work, the display went entirely blank and I had to cycle the power to bring it back to work. On other 2 or 3 occasions it reported cell capacity twice as larger as it really was - I had a 1840mAh Ni-MH cell in it and the charger after charging the cell reported 3600 mAh. There would be no way for a AA Ni-MH cell to have such high capacity, especially if the cell was not a new one. So it seems the firmware has some bugs and could be better. Also, despite of claiming so it was not able to properly identify Ni-Cd type of cell.

Overall though it seems to be an OK charger, it barely produced any heat if at all but I only powered it from a 2A 5V cell phone charger. It however makes sense since as can be seen from the board photos is has a few DC-DC converters so it should be fairly efficient.

[bc888]

I bought one of these when they first came out. Recently, that slot, #2, does not recognize a battery. It blinks for about 15 seconds and then reports "FULL". The other 3 slots are fine. I noticed some gunk on the contacts where the positive terminal is, so I cleaned it with Deoxit. Unsuccessfully.  Opened it up and what appears to be an unmarked capacitor is leaking. Started looking for a schematic and tripped over your post with the wonderful photos. In the lower picture, your capacitor that correspondents to my failing version is marked C38, mine has no markings of any sort.

Guess I'll try and find the value and replace it next time I'm in my shop, which might be a while since my wife has plans.  My purchase date was 1/27/2020.

[ralphrmartin]

Last time I looked, I couldn't see a "universal" charger that would also do NiZn cells - had to buy a separate charger.