Charger Yi Fang WS1


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Yi Fang Technology is a company selling chargers and batteries branded EFAN.

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I got the charger in a cardboard box with specifications on the outside.


The box contained the charger, a power supply, a car adapter and a instruction sheet.


The charger has a single 12V input for use with the power supply and car adapter.


The user interface is a small display and a single button.
The button can be used to select current, turn background light off/on and activate usb output.


The display shows voltage with two decimal places and animated battery symbols when charging.


Background light can be turned off or on with a long press on the button. Default is on when power is connected.
Like many other chargers it is missing a dedicated battery full indicator, you have to look at the animation. It will stop with all blocks in the battery shown, when the battery is full.


The charger has a usb output connector, that can be used with one or both batteries.

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The slots uses the typical design with a slider. They are with metal rails, but the slider is not moving very smooth.
The slots can accept batteries from 31 to 71.2 mm.


The charger is marked with some of the supported battery sizes, but is missing NiMH batteries and 10440. The label on the backside do include them.


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


Charging LiIon


At 0.25A the charger does a nice CC/CV charging with about 20mA termination current. This low termination current is good for smaller cells.


At 0.5A the charger has the same nice CC/CV curve and 20mA termination.


And also at 1A. Here the 20mA termination is on the low side and makes the charging take longer than necessary.


The second channel is also charged fine.


With the 2600mAh battery the charger voltage is around the maximum allowed voltage for a short time during the charge. I do not believe it has any significant effect on the battery, but I would have prefered the voltage had been slighty lower.


Nice CC/CV charging.


The charger does also handle this old cell very nice, but it does not get much charge at this high current.


A more realistic charge current for this old cell will put more energy into it.


Two more normal small cells are charged fine.


Using both channels is no problem, there is full current for both cells.


The charger uses about 1A at 12 volt.


M1: 40,9C, M2: 39,2C, M3: 40,7C, M4: 42,9C, HS1: 56,1C

Battery temperature looks as expected and as usual there is som hot parts inside the charger.


M1: 39,2C, M2: 41,0C, M3: 41,9C, HS1: 59,2C

The usb output is leading the heat to the outside. It might be a bit hot to touch during charge.


The charger needs 4 seconds to initialize.


Current can be changed at any time during charge.

Charging NiMH


With 0.25A current the cell is charged fine and terminated at a good time.
I wonder about that termination, it it due to a 0dv/dt or due to a timeout?


With 0.5A current the termination looks like maximum voltage termination, but the cell is full as can be seen on the temperature curve.


At 1A it is also a maximum voltage termination and it might be a bit early.
The charger has about 50mA trickle charge here (It is changed with charge current).


Second channel look similar.


With the XX cell the temperature raise is present, i.e. the cell is filled.


Same with the Powerex.


The AAA is also a little bit short of full.


The charger is fairly fast at detecting a full cell.


Two eneloops is no problem and this time there is a temperature raise.


With an external power supply I can see the charger uses about 0.5A at 12V when charging.
It does not uses 300mA when trickle charging, that is more like the maximum current.


Same as the above curve, but with input current removed. The trickle charge does not look like it is reduced after some time.


M1: 43,1C, M2: 41,6C, M3: 49,3C, M4: 39,7C, HS1: 57,1C
NiMH do get slightly hotter than LiIon, but not much.


The charger only need 3 seconds to start a NiMH charger.


Again the current change can be used at any time.
The measurements pulses are used to check the battery voltage without current on and are also the reason for the pulsing input current.


The trickle charger is done with pulses at selected charge current. There is about 40 seconds between the pulses.


Here is a trickle charge pulse with selected current at 1A.

USB output


The USB output can deliver 1.1A from battery #1, but it does not shut down the output when overloaded.


Battery #2 works the same way.


When using both batteries at the same time, the output can easily deliver 2A, at least with newly charged batteries.


A single battery in either slot can easily deliver 0.5A for more than 3 hours. The output is disabled at about 2.7 volt on the battery.


With both slots containing batteries the runtime is doubled. The batteries are not discharged at the same rate.
Notice: The efficiency calculations are invalid, I do only measure current on one battery.


Increasing the current to 1A does not look as good with a single battery. The 5 volt output can only be maintained for about 1 hour.


Using two batteries works much better, but when the first battery is empty, the output voltage drops.


At 1A load the usb output has 57mV rms and 510mV pp noise in the output, measured with full batteries.


At 0.5A load the usb output has 40mV rms and 380mV pp noise in the output, measured with full batteries.

The charger passed a isolation test with 2500 volt, but failed a 5000 volt test, this makes the charger acceptable for 110VAC usage, but doubtful for 230VAC usage (Not good when the supplied adapter is for EU). Usage with 12 volt (in a car) is, of course, always possible and safe.


With the low termination current and low current ranges this charger is good for charging 10440, 14500, 16340 cells, but it can also be used for 18650 or 26650.
With NiMH it uses the usual maximum voltage termination, i.e. battery may not be fully charged.
The usb output does 0.5A fine but need two batteries to do 1A fine and I could have wished for less noise.

I like the charger, it can be used for many charging purposes, but it need a better power adapter.


The charger was supplied by Yi Fang for review.

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