XTAR VC4 Charger for Lithium-ion and Ni-MH Batteries (Authentic USA Version)

Increasingly I need to charge/test Lithium-ion cells of various sizes. The reasons I picked this charger (XTAR VC4) instead of the Opus BT-C3400:1. I like trying out new chargers. The Opus BT-C3100/3400 is too similar to the BT-C2000 which I already own, while the XTAR VC4 has an interesting new display.2. I'm a cheapskate. The VC4 is about half the price of the C3400.3. (This I found out after my purchase) The VC4 has two wider outer slots that can accept up to D-cell. The C3400 can only accept up to C-cell.The XTAR VC4 has an unusual design. To start with, it is powered from USB port instead of from AC. This makes the unit lighter and independent from AC line voltage. On the flip side, you must already own a reliable AC-to-USB adapter that can sustain 2.1 Amp.I have tested charging Li-ion cells ranging from 14500 to 26650, and NiMH cells from AAA to D size. The charger can accept 4 cells up to 20650 size. When charging larger cells such as 26650 or D-cell, only the outer two slots can be used. The fitting is very tight for D-cell but it works.[Display]The LCD panel is divided into two halves. Each side shows the battery voltage (V) in an analog meter, and the charging capacity (mAh) in digital. If you insert more than two cells, only the status of the last two cells are displayed. But you can press the SELECT button to toggle the display between cells.The central current meter shows the maximum charging current. Typically it says '1.0A' when only the two outer slots are in use, '0.5A' when more slots are in use. However not all cells are charged at the same current at the same time. For Lithium-ion cell, the current will drop gradually while the cell is close to being fully charged. This is completely normal. I have also seen some old NiMH cells being charged at 0.2A instead of 0.5A.In addition, each channel has an LED indicator. It turns Red while charging; Green when done. This is a nice touch.[Great Features]There are several features I especially like about this charger:1. This charger is very intelligent in determining the battery chemistry. It can tell if the cell insert is NiMH, Li-ion or alkaline, and select the charging algorithm accordingly.2. Even if a NiMH cell is over-depleted to nearly zero volt, this charger can still detect it and charge it up. In contrast, most Smart chargers (such as La Crosse BC1000 or Opus BT-C2000) have problems detecting over-discharged cells.3. It can accept old cells with higher internal impedance. Apparently if a cell with higher resistance is detected, the charger switches to lower current. In contrast, many other smart chargers (such as the Panasonic BQ-CC55) will simply reject the cell.[Quirks/Improvements Needed]1. It does not have a Discharge mode to determine the true capacity of a cell. Instead, you can only estimate the capacity based on the charge a cell took in during charging - assuming the cell was fully depleted initially. Typically a cell will take in more charge than its actual capacity. For Li-ion cell the difference is negligible, but for NiMH the error can be 5% or more (especially if the cell is in bad shape).2. The current meter does not always give the correct information. For example: when I tested charging an alkaline cell, the 'NiMH' sign lights up. Current meter says charging current is 1A, but actual input to the charger is just ~100mA. That means the actual current to the cell is probably ~50mA (because the charger itself consumes ~50mA in standby mode)3. I'm not yet convinced that the VC4 correctly terminates charging of all NiMH cells. For example, I once recharged three AA NiMH cells and the VC4 reported the same charge of 2209mAh each. I then discharged those three cells on my BT-C2000, and it reported 2041/2048/1779mAh!I repeated this test with those three cells, and observed essentially the same results. Next, I tested two different cells. Charging on VC4 took in 920mAh each, but discharging on BT-C2000 reported 730/1765mAh! More investigation is needed.[Bottom Line]The XTAR VC4 is inexpensive yet very versatile. So far it works great fro me in charging Li-ion and NiMH cells of different sizes. I especially appreciate the fact that it can recharge very old or completely depleted NiMH cells. In fact it does a better job in this aspect compared to all my other advanced chargers. For this reason I give it a 5-star rating despite of its quirks.

I am providing this same review on multiple products listed below.Background – In August 2014, I bought a bicycle headlight (3800 lm, 3x Cree T6 LED lights) through Amazon. I ride 1-2 times per week for ~1 hr 45 min each time and use my headlight constantly (day or night) for safety reasons. This is not a review of the headlight (of which there are hundreds of similar ones available) but I will say that a) I like the headlight very much but b) 3800 lm is ridiculously bright and if I were to do it over again, I would go for something in the 1000-2000lm range. The original batteries (some generic Chinese brand) provided power for my rides but had to be recharged each time. After ~2 years, the batteries would no longer last for my full ride. Thus, the hunt for new batteries started.Tigervivi 8.4v 6400mah Silicone Waterproof 4 x 18650 Rechargeable Battery Pack for Headlamp & Bicycle Light – If you are reading this, you have probably found, as I did, that buying replacement batteries for your high power headlight is not all that easy. I bought the above battery pack for $13.86 in July 2016. Do not waste your money. Out of the box, this battery pack would not last a single ride for me. Based on comparison with detailed measurements I made on subsequent battery buys, I estimate the actual output of this battery pack at 800-1000mAh. If you are happy with that for $14, go for it. Otherwise, read on. Either way, I give this 1 star for misrepresenting the product output.I did find a good solution but it’s much more expensive than even the original $20 headlight. Regardless, I am quite happy with it…read on.Hanperal 4 X 18650 Water Resistant Battery Pack Case House Cover for Bike Bicycle Lamp – In July 2016, I bought a battery case for the 18650 batteries that power these high power bike headlights. The case I bought was a different brand (Solarstorm 2S2P 18650 battery case) and was GearBest.com but it looks absolutely identical to the above mentioned case that is available from Amazon for $15.99. (I paid $8 from GearBest.com.) The case seems to be well made and allows for individual removal of the 18650 batteries. The top also has an o-ring seal to help keep water out and a DC plug that works with the cheap DC charger provided with the original headlight to charge all four 18650 batteries in the case. I’m not rating the Hanperal case (since I can’t swear that it’s the same as what I have) but I am very happy with the one that I bought.SunLabz 18650 3.7V Rechargeable (4-Pack) Flat Top Battery Cells 3400mAh – The batteries made me the most nervous since they don’t even have a brand name on them, I haven’t ever heard of SunLabz and my experience with the Tigervivi battery pack left me feeling less than trusting. On the recommendation of a friend, however, I went ahead and bought these. Since I bought a nice little battery charger (discussed below) that provides a measure of how much energy each battery is taking in, I was able to fully discharge these (I know…not good for the batteries) and fully charge them to verify the capacity. I am very happy to say that all four came in at 3460-3525 mAh so I can recommend these without hesitation. At the $19.95 price I paid, they are not exactly cheap but are a good value considering the high power level that they can handle. I get a full three rides using these (i.e., >5 hours of continuous operation) after which the indicator button on my headlight turns red (although the headlight is still burning brightly). These measurements formed the basis for my estimate on the meager capacity of the Tigervivi batteries reviewed above. (Consider this…each SunLabz battery has almost double the capacity of all four Tigervivi batteries combined).XTAR VC4 Charger for Lithium-ion and Ni-MH Batteries – I bought this charger before I confirmed that I could charge my entire battery pack using the simple charger that came with my headlight. Nevertheless, I am quite happy with this $21.75 charger. It is compact, flexible (multiple battery capability), auto-detects the battery type and provides meaningful data on the batteries being charged (which speaks to the engineer in me). Even though it turned out that I didn’t need this charger, I have been happy to keep it and have ended up charging a bunch of Ni-MH batteries that I have bought since. I will say that it was delivered with scratches on the faceplate which may indicate poor handling by Schenzhen Precious Technology, Ltd (the seller) or even that the unit was used. However, it performs so well that I chose not to reduce its score on that basis.Bottom line – it took a lot more effort than I thought it would or think it should but I did find a truly excellent solution to my bike headlight battery problem that I hope is helpful to others as well.