Test/Review of Charger Xtar VC2

HKJ

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[size=+3]Charger Xtar VC2[/size]

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Xtar makes many LiIon chargers, this is a usb powered dual channel charger with display. The charger can charge with up to 0.5A for each channel, but the current is not user adjustable.



I got the charger in a small cardboard box with the specifications printed on it.

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Inside the box the charger was in a small fabric bag, this can be useful if it is used as a travel charger.

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The bag contained the charger, a usb cable, a warranty card and a instruction manual.

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The charger is usb powered from a micro usb connector, but there is not a power supply included, i.e. you must supply your own usb power supply/charger. With a maximum charger current of 1A the charger works best with high power chargers, but will reduce its current if the power supply is overloaded.
I have tested a few usb power supplied.

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There is only a display as user interface, no buttons or switches.

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The display uses dials to show voltage and maximum current, it does also have some 7 segment digits to show charged capacity.

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The current dial only shows the maximum charge current, the actual current is lower when the battery is in the CV phase.
The voltage dials shows the actual voltage when in range:
0V Battery voltage is low, charger is only using low current, display may show "Err" if there is a problem with the batteries.
3.0V Voltage is high enough to start regular charge.
3.5V-4.2V Regular charge, display is within 0.1 volt.

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The charger can handle both button top and flat top batteries.
The slider moves smoothly and can hand cells from 30mm to 71 mm long.

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The charger can handle 71 mm long batteries, including flat top cells.



[size=+2]Measurements charger[/size]


  • When charging the last digit in the capacity displays will flash.
  • The charger will charge with 2.4mA from 0 volt and display will show "Err"
  • At 0.2 volt it will start charging with 340mA (It will be down to 180mA 2.9 volt) at and display will show mAh.
  • At 2.9 volt regular charge current will be applied.
  • When charging two batteries with reduced current, they may not charge at the same speed.
  • When charge is finished the charger will charge with 0.3mA.
  • Charger will restart if voltage drops to 3.9 volt.
  • Charge will restart charging after power loss, or battery insertion.
  • When not connected to power it will drain about 0.1mA from a battery.
  • Current dial will show maximum possible charge current, not actual charge current.
  • Charge current steps down if usb voltage drops too much and may step up if usb voltage recovers (Like when one slot is finished).
  • Voltage dial will show within 0.1 volt when voltage is above 3.5 volt, between 4.1V and 4.2V is does also have a 4.15V position.
  • Voltage dial is within 0.1 volt when voltage is above 3.5 volt.
  • The 3 volt position on the voltage dial looks like it signals "start of regular charge", i.e. 2.9 volt.
  • mAh display flashes "Full" when the corresponding battery is full.
  • The background light will flash when at least one battery is full.

The light green line is usb current consumption, the dark green is charge current.

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The charger does a nice CC/CV charge with a termination at about 50mA. There is some oscillation during the final part of the charge, but it does not affect the result.
The display shows 2918mAh charged into the battery.

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The other channel has a similar result.
The display shows 2932mAh charged into the battery.

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The 2600mAh battery has a very long CV phase, probably because it is getting old.
The display shows 2549mAh charged into the battery.

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The 3400mAh takes slightly longer to charge.
The display shows 3254mAh charged into the battery.

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The charger has no problem with my old IMR cell.
The display shows 177mAh charged into the battery.

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The display shows 715mAh charged into the battery.

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The display shows 784mAh charged into the battery.

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Supplying a falling voltage to the charger shows that the current regulation works at around 4.7 volt. When the voltage gets below 4.7 volt the charger will start reducing charge current, until the voltage is above 4.7 volt again. If this does not happen the charger will stop completely.

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To see the current limiter in function I put a 1ohm resistor in series with the power supply, this simulates a fairly bad usb power supply.
As can be seen the charge current is reduced, but the cell is fully charged.
The display shows 2791mAh charged into the battery with 0.3A current.

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With two batteries and 1ohm in series with the power supply the charger has to limit the current even more. This shows that the two channels is not balanced, there is a significant difference in charge current (This cannot be seen in the chart). After 23½ hour the mAh count was 2088 and 2746. When the second cell finished (At 1500 in the chart), the first cell was charged at a much higher current.
The display shows 2846mAh and 2904mAh charged into the battery with 0.1A current.

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With two batteries and a stable 5 volt power supply the charger will use about 500mA for each battery when charging.
The temperature raise is very limited.

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M1: 24,8°C, M2: 24,7°C, M3: 27,4°C, HS1: 33,8°C
There is no doubt about where the heat generation is, but actual temperature shows that it is a insignificant heat generation.

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M1: 24,7°C, M2: 24,3°C, M3: 28,0°C, HS1: 36,4°C

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The charger needs about 6 seconds to start.

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But if the power is limited it will use some more time to adjust the charge current.

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The scope traces looks very smooth, but that is only because I filters them. The charger is using a unfiltered 62kHz charge current.

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When current is reduced the charge will dynamically adjust the current.


Because the charger is supplied from usb power there will not be any safety issues with it, but be careful with the usb power adapter.



[size=+2]Conclusion[/size]

The actual charging is very good, but is a bit slow or very slow, depending on the usb supply used. The charger can draw a lot of current from the usb port, it will not be a problem with most usb chargers and power banks, but I wonder how a PC usb 2 ports will handle it.

The charger is a nice for car and travel usage and can also be used at home, but it is a good idea to find a power supply that can supply enough current and voltage for full charge speed. Remember to use a short cable between power supply and charger to avoid slow down due to losses in the cable.

I will call it a good charger.



[size=+3]Notes[/size]

The charger was supplied by XTAR for a review.

Here is an explanation on how I did the above charge curves: How do I test a charger
 

Timothybil

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Nice review. Looks like a nice charger for Li-ion, but no NiMH. Does anyone make a comparable USB charger for NiMH? My emergency power setup right now is all USB, and I need a way to recharge my Eneloops.
 

UnderPar

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Thanks for this review. Am keeping an eye on this charger. Seems to be a good charger for us to know the real capacity of our batteries.
 

HKJ

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Thanks for this review. Am keeping an eye on this charger. Seems to be a good charger for us to know the real capacity of our batteries.

It does not measure the real capacity, only how much it fills into the batteries.
If you starts with an empty LiIon battery it will be fairly close to the real capacity.
 

KITROBASKIN

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If you often walk at night in a certain area for a basically the same amount of time (And you use the same mode settings), then you can determine about how many mAh your flashlight uses for that walk. This can help you gauge how long your light will shine to the ending state-of-charge you choose. That is, if you charge consistently each time. Handy

It does not measure the real capacity, only how much it fills into the batteries.
If you starts with an empty LiIon battery it will be fairly close to the real capacity.
 

incd

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I don't have quality power supply for rate 5V, 1A.

But I do have a good power supply rated 5V, 1.8A, is that ok to use it on this charger?
 

HKJ

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I don't have quality power supply for rate 5V, 1A.

But I do have a good power supply rated 5V, 1.8A, is that ok to use it on this charger?

It is perfectly fine.
With current you can always use a power supply with higher current rating.
 

KITROBASKIN

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The transformer/power supply that came with my iPad 2 offers the most amperage to charge two cells, compared with the cell phone units we have. Typically I will pull the battery once the meter shows charging 4.2 V. After they rest, the voltage is 4.06 to 4.12 or so, but I am not sure how long the charger has been at 4.2 volts.


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HKJ

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The transformer/power supply that came with my iPad 2 offers the most amperage to charge two cells, compared with the cell phone units we have. Typically I will pull the battery once the meter shows charging 4.2 V. After they rest, the voltage is 4.06 to 4.12 or so, but I am not sure how long the charger has been at 4.2 volts.

LiIon batteries are never fully charged when voltage read 4.2 volt, it has only reached the CV phase and it also needs some time before the battery is full (Usual ½-1 hour, but depends on a lot of factors).
 

Albinoni1967

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is it possible to use a 2amp USB wall socket charger with this device. Lets say for eg the charger that came with my Samsung Galaxy Note II has a 2amp charger and can I use it on this, or does it have to be a 1amp charger.
 

StandardBattery

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Ok thanks for that, just is on the back where the charge plug goes into it says 1 amp and I thought a 2amp one would ruin the charger.
That's a maximum rating not to be exceeded. The electronic device controls the amount of power it uses. The biggest issues with USB adapters is the variety of methods used to indicate to the device what the maximum power that is available. So the worst thing that would happen is the charger would think it had only 500mAh available and adjust it's charging accordingly. This is not very likely for a 1A requirement, or with this adapter or charger, but you don't have to worry about damaging either device.
 

Albinoni1967

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Also another question here re this charger, I noticed with the digital display the top display shows the amps the battery is being charged at, but can this be controlled or set manually or is it Auto. Lets say for eg on my XTAR VP1 on the front panel there is a button that I press to say what I want to charge the battery at, but does the VC2 have this as well or is it Auto and decides for itself
 

HKJ

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Also another question here re this charger, I noticed with the digital display the top display shows the amps the battery is being charged at, but can this be controlled or set manually or is it Auto. Lets say for eg on my XTAR VP1 on the front panel there is a button that I press to say what I want to charge the battery at, but does the VC2 have this as well or is it Auto and decides for itself

The display does not show the charge current, but the maximum possible charge current.
It cannot be adjusted, but depends on the USB power supply used, i.e. not on the batteries being charged.
 

KITROBASKIN

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The 350 mAh 10440 Efest batteries I use in my MBI HF do just fine, if a little slow, being charged from the CottonPickers charger at a nominal 100 mA but now when I want to charge it faster I can use the Xtar VC2 with an 18650 in one bay and the lower powered USB cell phone power supply that only charges each battery at about 350 mA. I believe that keeps the charging at about 1C for the small 10440. When it is charged, I pull it from the VC2, and the 18650 starts charging at ~500mA at that point.

Also another question here re this charger, I noticed with the digital display the top display shows the amps the battery is being charged at, but can this be controlled or set manually or is it Auto. Lets say for eg on my XTAR VP1 on the front panel there is a button that I press to say what I want to charge the battery at, but does the VC2 have this as well or is it Auto and decides for itself
 

HistoryChannel

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Great review! I just ordered 2 of these for portability. I have the VP1 for home charging but this VC2 will be great to use with a portable battery pack like the Anker 2nd Gen Astro2 9600mAh 2-Port 3A Portable Charger. And also with my 20w portable solar panel. I'll have a way to charge my 18650 batteries when I'm hiking now!

Thanks HKJ for your incredible reviews as always!
 
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