Charger Xtar VP4




Xtar has many good LiIon chargers, this is a 4 channel charger in their advanced charge line: VP1: 2 slots, 3 currents and voltage display, VP2: 2 slots, 3 currents, 3 voltages, voltage display and usb out. This new model has 4 slots, 2½ currents and voltage display. Compared to VP2 only the number of slots and the maximum battery size has been improved, other features are the same or downgraded.



The charger comes in a cardboard box with lots of specifications on it.



In the box is the charger, a power supply, a car adapter, a instruction manual and a warranty card.



The charger has a DC connector for power input. Because it can only charge with 1A on two channel, it only need a 1A power adapter. If more channels are used all will be reduced to 0.5A.



The slots have raised battery connections, i.e. flat top batteries can be used. The slider works very smooth and can take batteries from 30.5mm to 71.5mm. This is enough to handle even long protected 26650 batteries.



On the top of the charger is a switch to select charge current, it can select between 0.25A, 0.50A and 1.00A, the current will be the same in all four slots.
The charger will always select the highest possible current when loading it with batteries, the switch can then be used to reduce the current.
When only slot #1 and/or slot #4 is used the maximum current is 1A. If there is any batteries in slot #2 or #3 the maximum will be reduced to 0.5A.
Below the switch is the display, by holding the switch down the display can be turned off/on (but not the leds), this will not affect any function in the charger.



The display captured during startup where everything is turned on.



Regular charge, the battery symbol is animated when the charger is charging.



The charger has a led for each channel, making it very easy to see when it is finished.







The charger can easily handle 70 mm long batteries, inclusive flat top cells.



Measurements

• Discharges LiIon with 0.2mA to 0.3mA when not connected to power
• Charges with 0.2mA when LiIon battery is full.
• Below 1 volt the charger will charge with 1mA, the display will be empty and the led green.
• Between 1 and 2 volt the charger will charge with 33mA, the display will show voltage and the led will flash red.
• Between 2 and 3 volt the charger will charge with 85mA, the display will show voltage and the led be red.
• Above 3 volt regular charge current is used.
• In the regular charge range the voltmeter is within 0.01 volt, at lower voltages the tolerance is slightly larger.
• The meter updates the voltage reading fairly often (Better than once a second).
• The meter stops updating above 4.20 volt when the charging stops.
• Will restart if battery voltage drops below 3.90 volt.
• Charge will restart charging after power loss or battery insertion.
• If any battery is placed in either of the two center slots, the maximum charge current is reduced to 0.5A (A full battery in either center slow will also reduce the current).
• When charger is powered on display shows 0.5A charge current, but charger will automatic change to 1A if a battery is put in slot #1 or #4.
• Current select button will decrease current when pressed, i.e. 1A -> 0.5A -> 0.25A -> 1A

First charge curve shows a very nice CC/CV curve with a termination about 80mA. This is a very good charge curve.





The other channel does also work fine.





Different capacity batteries, need different charge time.



Reducing the charge current to 0.5A, does reduce the termination current to about 40mA and uses the same good CC/CV curve.



The 0.25A charge current uses a termination current of about 30mA.



Trying to provoke the charger with my old 16340 cell does not show any problems, the charger handles it nicely.



Reducing the charge current to the 16340, makes the curve more smooth.




A 14500 cell at 0.5A works fine.



Same with a 18350 at 0.5A.



With four cells the current is limited to 0.5A for all slots.



Using an external 12V supply, the charger draws nearly 1A while charging.



M1: 32,5°C, M2: 34,8°C, M3: 35,6°C, M4: 32,1°C, M5: 38,8°C, M6: 42,4°C, HS1: 43,4°C
With 0.5A charge current the batteries are not heated much.



M1: 33,0°C, M2: 35,0°C, M3: 35,3°C, M4: 32,9°C, M5: 44,6°C, HS1: 65,0°C
But inside some electronic do get warm.



The charger needs about 8 seconds to turn on and will always start charging at the highest possible current setting.



When selecting another charge current, the charger will decrease current fast and increase current slowly.



Testing the mains transformer with 2500 volt and 5000 volt between mains and low volt side, did not show any safety problems.



Conclusion

The charger can handle a wide range of battery sizes from 10440 up to 32650 batteries and has a good CC/CV charge curve. The display with the precise voltage readout makes it easy to check if batteries has been over discharged. The leds is a very nice feature, that makes it easy to see when batteries are charged.

It is a good charger with nice features, but not what many people had hoped for in a VP4 charger, i.e. 3 voltages and at least 3 currents.



Notes

The charger was supplied by Xtar for review.

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