Charger Xtar VC2S

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Xtar makes many chargers, this is a usb powered dual channel charger with display. The charger can charge with up to 2A for a channel, the current will depend on the internal resistance in the batteries. It can also work as a power bank.

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

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n the box was the charger, a usb cable and a instruction sheet in many languages.

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The charger is usb powered from a micro usb connector and it has a power bank output.

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The user interface is a display, two leds and one button to select what the display shows or turn on the usb output.

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When powered on the display will show all segments, the needle will start from zero and increase, I took the photo before the last needle was displayed.

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Charging one battery, the red/green leds always make it easy to see if the charger is finished.

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One press on the the button and the display shows the actual charge current.

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After next press it shows the internal resistance in the batteries.

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When used as a power bank the display shows the usb voltage and current.

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The specifications are on the back of the charger, but you need light from the right angle to read it and maybe a magnifying glass.

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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 70.5mm long.

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The power bank function only uses one battery and the slot is marked.

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The charger can handle 71 mm long batteries, including flat top cells.
The current for 10440 is on the high side even with the automatic regulation at minimum.



Measurements charger

Charging 4.2V LiIon

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This is a nice CC/CV charge curve with a termination around 100mA. The mAh display is rather optimistic.
Display shows 3437mAh 42mOhm

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Here the voltage is slightly higher and the termination is around 140mA
Display shows 3107mAh 47mOhm

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The 2600mAh battery looks similar
Display shows 2730mAh 50mOhm (Discharge test shows 2481mAh was charged into battery)

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This battery is older and has higher internal resistance, the charger reduces charge current.
Display shows 3214mAh 179mOhm

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It is the same with this battery.
Display shows 2515mAh 149mOhm

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This is a new 2600mAh high current battery and it is charged at 2A.
Display shows 2902mAh 50mOhm

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This larger cell is also charged at 2A
Display shows 3164mAh 20mOhm

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A 14500 cells is charged at low current.
Display shows 889mAh 146mOhm

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The same for my worn down 18350 cell.
Display shows 204mAh 146mOhm

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With two batteries in the charger the current is reduced to 1A for each cell.
Display shows 3489mAh 63mOhm and 3112mAh 41mOhm

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Adding 0.5ohm in series with the power supply forced the charger to reduce the current, but the measurement circuit is affect by this resistor, the cell is not 4000mA or 5mOhm.
Display shows 4074mAh 5mOhm and 3456mAh 5mOhm

Temp6056

M1: 34.6C, M2: 35.0C, M3: 36.1C, HS1: 44.1C

Temp6057

M1: 37.5C, HS1: 41.9C

PoweronLiIon

The charger pulses the charger current when starting a charge, this is used to analyse the internal resistance.



Charging NiMH

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My eneloop has been used a lot and the internal resistance is a bit high, this means the charger uses a low charge current. It looks like the termination is on voltage and a bit before the cell is full.
Display shows 1851mAh 103mOhm

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The second channel is the same.
Display shows 1538mAh 125mOhm

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The eneloop pro is also the same.
Display shows 2403mAh 82mOhm

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The Leise battery needs slightly lower voltage to be full and termination works much better here (A small temperature increase can be seen on the black line).
Display shows 2438mAh 67mOhm

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The AAA cell also stops a bit before it is full.
Display shows 700mAh 202mOhm

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Due to the voltage termination the charger is fast at detecting a full cell, it happens when it switches to full charge current.
Display shows 13mAh 81mOhm

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The charger can handle two cells simultaneous.
Display shows 1719mAh 76mOhm and 1506mAh 73mOhm

Temp6070

M1: 29.6C, M2: 30.1C, HS1: 35.8C

Temp6071

HS1: 36.4C

PoweronNiMH

This looks similar to LiIon, but the charge current is very low.

PoweronNiMH2

Using a longer timescale it can be seen that the charger switches to full charge current after about 4 minutes.

ChargingNiMH

As usual the charge current is turned off at regular intervals to check charge voltage when charging NiMH.



Internal resistance

RILiIon

I wonder about the difference between the two channels, they are not calibrated the same when checking LiIon.
The actual measurement circuit is very consistent, but will give a too low value.

RINiMH

With the NiMH both channels gives similar value. Again the measurement circuit is very consistent, but actual value is too low.



USB output (Power bank)
USBmeter

When using the usb output the current is shown, it is not a super precise meter, but gives an good idea about the current draw.

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The power bank function is rated for 1A and can deliver about 1.4A with a full battery.

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The usb output can also deliver current directly from the usb input, but there is no current limit (I stopped manually at 2.5A).

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Here I charge a battery at the same time and was drawing about 3.3A from the usb supply.
Efficiency will be low, because some of the energy is used to charge the battery, not for usb output.

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Running the power bank with a 0.5A load it can maintain the output for about 3 hours.

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At 1A the output is maintained about 2 hours, again with full voltage until the battery is empty.
The jump in efficiency at the start is when the display reduces background light.

10ohm

Noises is 47mV rms and 339mVpp

5ohm

Noises is 45mV rms and 360mVpp



Conclusion

The charger is good at charging LiIon, with NiMH it uses voltage termination without top-off charge and that means the batteries is charged slightly below full capacity.
The automatic current selection means that charge current is kept down at a fairly safe level.
This charger has a calibration problem on slot #1 for the mAh measurement, it shows way to much.

The usb output works fine and the display is nice, using only one cell means the output current is a bit on the low side.

I will rate it as fairly good.



Notes

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