Test/Review of Charger Skilhunt M4D

HKJ

Flashaholic
Joined
Mar 26, 2008
Messages
9,715
Location
Copenhagen, Denmark
[SIZE=+3]Charger Skilhunt M4D[/SIZE]

DSC_2542.jpg


DSC_2543.jpg
DSC_2544.jpg


Skilhunt usual sells flashlights, but has recently started on chargers. This charger is a universal 4 channel charger that can handle multiple chemistries and battery sizes. It does also work as a power bank.



I got the charger in a cardboard box with lots of information on.

DSC_2540.jpg


The box contains the charger, a power supply and a instruction sheet.

DSC_2546.jpg


The charger has a barrel connector for 12V power input and a usb output connector for power bank function.

DSC_2550.jpg


The user interface is a display and a single multi-function button.
Fast presses on the button will change the display between hour:min and capacity display.
Holding the button down for two seconds will change the current one step (300/500/700/1A) for all slots.
Holding the button down for 5 seconds will select LiFePO4 for all slots.

DSC_2551.jpg
DSC_2552.jpg


First display shows normal charging with 300mA, one LiIon and two NiMH cells.
The second displays shows that the power bank function has been activated (it will not stay on).

DSC_2547.jpg
DSC_2548.jpg


The charger uses the common slider construction and will handle batteries from 31 mm to 71 mm, this means just about any cell.

DSC_2866.jpg


The charger exist in both the usual black and a sand colored one.

supportedBatteryTypes.png


supportedBatterySizes.png
DSC_2553.jpg
DSC_2554.jpg
DSC_2555.jpg


DSC_2556.jpg
DSC_2557.jpg
DSC_2558.jpg
DSC_2559.jpg
DSC_2560.jpg


DSC_2561.jpg
DSC_2562.jpg





[SIZE=+2]Measurements[/SIZE]


  • Discharges LiIon batteries with 34mA when display is on and not connected to power.
  • Discharges LiIon batteries with 0.7mA when display is off and not connected to power.
  • Discharges NiMH batteries with 0.1mA when not connected to power.
  • Charges LiIon batteries with 0.4mA when connected to power.
  • Charges NiMH batteries with 2mA when connected to power.
  • Will restart charging if voltage drops below 3.9 volt.
  • Charger will restart charging after power loss, or battery insertion.
  • Voltmeter is frozen when charging is finished.
  • Voltmeter is withing 0.04 volt on LiIon range (Current=300mA).
  • Voltmeter is withing 0.01 volt from 0.95 volt to 1.5 volt.
  • With 0 volt on a battery the current is about 2.3mA, enough to reset protection.
  • At about 0.5 volt battery voltage the charger will reconize the battery
  • Above 2 volt the charger assumes LiIon.


[SIZE=+2]LiIon[/SIZE]

Skilhunt%20M4D%201A%20(PA18650-31)%20%231.png


This looks like a good CC/CV charge curve with 100mA termination.
Display shows 2737mAh

Skilhunt%20M4D%201A%20(PA18650-31)%20%232.png

Skilhunt%20M4D%201A%20(PA18650-31)%20%233.png

Skilhunt%20M4D%201A%20(PA18650-31)%20%234.png


The other 3 channels looks just as good.
Display shows 2749mAh, 2785mAh, 2653mAh

Skilhunt%20M4D%201A%20(SA18650-26)%20%231.png

Skilhunt%20M4D%201A%20(PA18650-34)%20%231.png


These two cells are also handled fine.
Display shows 2418mAh, 2878mAh

Skilhunt%20M4D%201A%20(BE18650-26)%20%231.png


The older cell is no problem, but do, of course, take longer to charge.
Display shows 1956mAh

Skilhunt%20M4D%200.3A%20(PA18650-31)%20%231.png


Here I am using 0.3A charge current, but the termination is still at 100mA, this is not ideal.
Display shows 2346mAh

Skilhunt%20M4D%200.5A%20(AW18350-IMR)%20%231.png

Skilhunt%20M4D%200.5A%20(KP14500-08)%20%231.png


The smaller cells charge fine at 0.5A, but I would have like a lower termination current.
Display shows 551mAh, 665mAh

Skilhunt%20M4D%201A%20(4xPA18650-31).png


All four channels charging at 1A, works nice.

Skilhunt%20M4D%201A%2012V%20(4xPA18650-31).png


Charging four LiIon cells requires nearly 2A from 12 volt.

Temp2766.png


M1: 38,9°C, M2: 40,8°C, M3: 40,4°C, M4: 39,2°C, M5: 40,2°C, M6: 43,7°C, HS1: 56,8°C
Some heat is generated at 1A charge current, but not too much.

StartupLiIon.png


The charger is fairly fast to start and when powered on it will always start with lowest charge current.

CurrentChangeLiIon.png


Charge current can be changed at any time, just hold down the button for about 2 seconds to select next current.



[SIZE=+2]LiFePo4[/SIZE]

Holding down the button for 5 seconds will select LiFePO4 mode for all slots, it is possible to change current.
When finished charging LiFePO4 cells the display will flash as a reminder to remove the cells.

Skilhunt%20M4D%201A%20(18650-LiFePO4)%20%231.png


This is a good LiFePO4 charge curve.

Skilhunt%20M4D%200.3A%20(Soshine-LiFePO4)%20%231.png


The AA sized cell is also charged good, but again I would have like a lower termination current.


[SIZE=+2]NiMH[/SIZE]

Skilhunt%20M4D%201A%20(eneloop)%20%231.png


It looks like the charger terminates on voltage and may be a little bit early, but not much.
Display shows 1981mAh

Skilhunt%20M4D%201A%20(eneloop)%20%232.png

Skilhunt%20M4D%201A%20(eneloop)%20%233.png

Skilhunt%20M4D%201A%20(eneloop)%20%234.png


The same on the other slots.
Display shows 1801mAh, 1991mAh, 1912mAh

Skilhunt%20M4D%201A%20(eneloopXX)%20%231.png

Skilhunt%20M4D%201A%20(eneloopPro)%20%231.png


On the XX a very small temperature raise can be seen, Pro has more temperature raise, i.e. they are full.
Display shows 2561mAh, 2659mAh

Skilhunt%20M4D%201A%20(powerex)%20%231.png


This cell is getting old and it is very hard to terminate correctly, the charged missed termination and filled 9000mAh into the cell.
Display shows 9285mAh

Skilhunt%20M4D%200.3A%20(eneloop)%20%231.png


A low current charge cannot terminate on -dv/dt, but because this charger uses voltage termination it terminates fine and soon after the cell is full.
Display shows 2018mAh

Skilhunt%20M4D%200.5A%20(eneloopAAA)%20%231.png


The AAA cell do also look fine.
Display shows 718mAh

Skilhunt%20M4D%201A%20full%20(eneloop)%20%231.png


Terminating on voltage, it can detect a full battery very fast.
Display shows 28mAh

Skilhunt%20M4D%201A%20(4xeneloop).png


Four cells at 1A is handled just as fine as one cell, except everything gets a bit warmer.

Skilhunt%20M4D%201A%2012V%20(4xeneloop).png


Charging four NiMH batteries requires about 1A from 12 volt..

Temp2773.png


M1: 41,5°C, M2: 43,5°C, M3: 43,0°C, M4: 40,7°C, M5: 38,3°C, M6: 44,9°C, HS1: 61,7°C

StartupNiMH.png


Again about 4 seconds in startup time.

CurrentChangeNiMH.png


The current can be changed at any time by holding the button down for about 2 seconds.
With NiMH the charger turns the current off to measure voltage.






[SIZE=+2]Power bank[/SIZE]


  • USB output is coded as Apple 1A.
  • USB output is off when power is connected.
  • USB output will turn off in 10 seconds when load is below 85mA.
  • The power bank uses all mounted batteries.

Skilhunt%20M4D%20(PA18650-31)%20%231%20load%20sweep.png


The usb output can maintain voltage to a bit above 1A and the overload protection will kick in at about 1.4A

Skilhunt%20M4D%20(4xPA18650-31)%20load%20sweep.png


With more batteries in the charger, the output voltage is maintained to a higher current, but the overload protection is the same.

Skilhunt%20M4D%20(PA18650-31)%20%231%20usb%20out%2010ohm.png


With one battery the power bank output looks very good at 0.5A load.

Skilhunt%20M4D%20(PA18650-31)%20%231%20usb%20out%205ohm.png


But totally hopeless with 1A load.

Skilhunt%20M4D%20(4xPA18650-31)%20usb%20out%205ohm.png


Using four batteries for 1A load will help, but it is not perfect.
Note: My efficiency curve is not valid, battery voltage and battery current is only for one of the four cells.

10ohm.png


The noise is very low at 0.5A: 6mV rms and 65mVpp

5ohm.png


With a fresh battery it is also very low at 1A: 8mV rms and 80mVpp, but as can be seen above the output gets unstable when the batteries runs down.

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



[SIZE=+2]Conclusion[/SIZE]

The charger is good at LiIon including LiFePO4. Generally it also do a good job on NiMH.
The power bank function only works for low current charging, I wonder why it uses the Apple 1A coding, even Apple has switched to usb charger coding for 1A.

As a charger I will call it good.



[SIZE=+3]Notes[/SIZE]

The charger was supplied by Skillhunt for a 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
 
Last edited:

kreisl

Flashlight Enthusiast
Joined
Jul 5, 2012
Messages
2,244
Interesting charger, thanks for the great review!
 

hammerjoe

Enlightened
Joined
Jan 15, 2015
Messages
220
Hjk,
Thank you for your review.
You mentioned that for nimh it terminates on voltage only so for the powerex battery did you figure out how did it decide to stop charging? Timeout perhaps?
 
Last edited:

HKJ

Flashaholic
Joined
Mar 26, 2008
Messages
9,715
Location
Copenhagen, Denmark
Hjk,
Thank you for your review.
You mentioned that fornimh it terminates on voltage only so for the powerex battery did you figure out how did it decided to stop charging? Timeout perhaps?


Maybe the voltage got high enough or more probably a timeout.

I have ordered some new powerex batteries and if I get time I will add a trace with them. My current batch of powerex is worn a bit too much.
 
Top