Charger Woyum ZK1a




This is a simple LiIon and NiMH charger that is powered from usb and has a fixed charge current.



It arrived in a cardboard box with a lot of specification on it.



The box contained the charger, a instruction sheet and an usb cable.



The charger is usb powered with a micro usb input.



There is no buttons on the charger, only a white dome with a multicolor led behind.



The color of the dome changes with charge state, green is charging done or no battery in charger and red, blue and purple during charge.



The specifications are on the bottom of the charger.



The charger uses the classic slider construction and will handle batteries from 33mm to 77mm, this will handle even the longest protected cells.







The charger can handle up to 70mm long batteries. Some small cells can be charger, but only if they are rated for 1A or more in charge current.



Measurements

• Power consumption from usb when idle with no batteries is 13mA
• Charger will discharge a full LiIon battery with less then 0.1mA when not powered.
• Below 0.6V the charger will not detect a battery
• Between 0.6V and 1.2V the charger will use low charger current (About 200mA).
• Between 1.2V and 2.1V the charger assumes NiMH
• Between 2.1V and 3.2V the charger will use low charger current (About 100mA).
• Above 3.2V the full LiIon current will be used.
• Will silent restart charging it voltage drops.
• Will restart charging if battery is inserted or power cycled.

Charging LiIon



The charging is a CC/CV voltage charge with about 100mA termination current.



During the charger it uses up to about 1A from usb (This is the same charge as above).




These two cells also looks fine.



But with this older cell the automatic restart kicks in due to voltage drop from the cell.



A larger high current cell is charged fine.



Adding 0.5ohm resistance in series with the power supply to simulate a long cable or weak supply shows that the charger will reduce usb and charge current, but the charging works fine.



M1: 32.9°C, HS1: 54.3°C



HS1: 42.2°C



The charger needs a few seconds to start, during that time the dome shows a couple of different colors.



The charger pauses the charge current at regular intervals, but it is obvious not using it for a simulated CC/CV curve.



The discharge current when not power is fairly low.



Charge do not like an unstable voltage from a solar panel.



Charging NiMH



This is a typical -dv/dt charge curve without any top-off or trickle charging. It looks good.




The two high capacity cells are also charged fine.



The current is slightly high for a AAA cell, but it is charged.



As usual a -dv/dt charger needs some time to detect a full cell, this charger is fairly fast with 10 minutes.



M1: 39.0°C, HS1: 56.2°C



HS1: 40.5°C



The charger needs a few seconds to start, during that time the dome shows a couple of different colors.



And as usual with NiMH chargers it pauses to check voltage.



Charge do not like an unstable voltage from a solar panel.



Conclusion

The indicator dome is unique design, compared to the usual small led or LCD display, it works fine and can be seen from any direction and a long distance (Except in bright sun). The charger works fine with both LiIon and NiMH, but is not ideal for old cells and small cells.

I will rate it a good charger.



Notes

The charger was supplied by Woyum for review.

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