Charger Xtar WP2s



Xtar makes many good chargers and does also sometimes updates their models. This is an update to the WP2 II, the update includes more selectable charge currents and more power on the usb output. The charger has two channels, i.e. it can do two cells independently of each other.



It comes in a cardboard box with a view to the charger and specifications on the back.



I got the charger, a manual, a warranty card and a car adaptor, but Xtar forgot to add a power supply.
Normally the power adapter is included and the car adaptor may be included.




This version of the WP2 has a cover over the batteries. This is an advantage when using it as an usb power supply/charger, because it is easier to put in a bag or pocket while loaded with batteries.



The control panel has 6 leds and one button:
3 Leds to show selected current (0.25A, 0.5A or 1A).
1 Led to show that usb output is activated.
2 leds to show charge status for the batteries (red=charging, green=done or no batteries, not used when usb output is activated).
The button will select charge current, when power is connected and a long press will activate usb output when power is disconnected.



The power input is a 12 volt DC connector, it can either be powered from the car adapter or the mains adapter.
The usb output must be activated with the button and will stay on until deactivated or the batteries are empty.



Xtar has a special label on, that makes it possible to check for counterfeit chargers.



The charger can handle both button top and flat top batteries, from 30mm to above 70 mm. The slider works well.






The charger can handle 70 mm long batteries, including flat top cells. (See my 18650 LiIon comparison for length of different brands).
It is possible to charge one 26650 in the charger, but it might be necessary to use some tinfoil at the minus pole.




Measurements charger

• Will discharge battery with about 4mA when not connected to power.
• Will discharge battery with about 0.25mA when connected to power.
• Will restart charging at 3.9 volt
• Will restart charging when battery is reinserted or power is cycled.
• Below 1 volt the charger will show a green light and charge with 2.5mA.
• Between 1 and 2 volt the charge will show a blinking red light and charge with 2mA.
• Between 2 and 2.9 volt the charge will show a red light and charge with 50mA to 65mA.
• Above 2.9 volt it will apply selected charge current.
• The channels on the charger are independent, i.e. there are small differences between them.

This charger has a very good CC/CV curve, this is an improvement from the old WP2 model that simulated it. The charge time is just below 4 hours.





With smaller capacity the charge time is slightly shorter.



The second channel works the same.



With 0.5A on a 3100mAh cell the charge time is considerable longer. The termination current is lower at the 0.5A settings, this is very good.



The lower current is for smaller cells.



0.25A requires a lot of patience (nearly 12 hours) with a 3100mAh cell.



My old 16340 cell charges perfectly on this charger.



Even at 1A the charger can handle it.





The charger is using a slow ramp up of the current in all modes.



USB output

The WP2s can power the usb output with one or two batteries. The cells are not directly in parallel (I had to use 5 DMM's to log it).

• Will discharge battery with about 4mA when not connected to power.
• USB output is coded as Apple 2.1A
• USB output will stay on when load is removed, on/off is only controlled with the button.
• USB output will always be off when charge power is connected.

Doing a load sweep with two batteries, showed that the current limit is at 2.4A, this is very good for a 2.1A supply.



A test with 2A current, shows a rather short runtime and also that the two batteries is loaded differently.
The termination voltage is rather high for this load (That is the reason for the short runtime).



Reducing the load to 0.5A works better, this gives 3 hours runtime with a single 18650 cell.



And four hours runtime on the other battery. This is strange behavior.






This is the same with other cells.



There is not much noise in the output, even at full current (10 mV).



At 0.5A the noise is down to 4.5 mV.



Conclusion

This charger does a good CC/CV charging and with 3 current settings it can handle a wide variety of cell sizes.

The usb output has very low noise in it and the ability to supply 2A, makes it useful for a lot of usb equipment, but due to the Apple coding on the connector, some equipment will not charge at full speed. The difference between the two batteries is silly and will hopefully be fixed soon, but the only downside is shorter runtime.
The charger has a rather high current drain on the batteries, this is absolutely no problem for the charging part, but it will not be a good idea to keep batteries in the charger for weeks. There is no battery power status indication for the usb output.

The charger is a very good LiIon battery charger and a acceptable usb charger.



Notes

The charger was supplied by XTAR for a review.
All the tests were done with my own 12 volt 1A supply.

Here is an explanation on how I did the above charge curves: How do I test a charger
Read more about how I test USB power supplies and chargers