Charger and power bank Miller ML202 V4

DSC_3538 DSC_3540

Miller is mostly know for the ML102 charger (V9, V8, V7, Old ), but they have a few other products. This here is basically a dual slot version of the ML102 with both charger and usb output.

DSC_3537

The actual packing of the ML202 is only a plastic bag without any accessories.

DSC_3543

The charger/power bank is a closed box. The cover is locked in position, but it is easy to remove it.

DSC_3541

The charger has a micro usb power input for charging current.

DSC_3539

And a large usb connector for usb power output.

DSC_3553

The charger has a couple of leds inside the transparant box:
Red: Charging
Green: Battery full
Blue: Usb output is on.

DSC_3554 DSC_3555

The charger will only fit one battery length and that is 65mm, i.e. unprotected 18650 cell, it is possible to use both flattops and some buttom tops.

supportedBatteryTypes

supportedBatterySizes DSC_3544

The charger can only handle unprotected flat top cells.



Measurements


ML202%20(PA18650-31)%20%231

This is a nice charge curve, charge current is 1.3A and termination current is 0.1A with a good CC/CV charge profile.

ML202%20(PA18650-31)%20%232

The other slot looks the same.

ML202%20(SA18650-26)%20%231

A 2600mAh cell is also charged fine.

ML202%20(2xPA18650-31)

There is no problem running two cell at a time, but the usb charger/power supply must be able to supply 2.5A to maintain full charge speed.

ML202%200.5ohm%20(2xPA18650-31)

Adding a resistor in series with the power supply to simulate a weak usb charger will reduce the charge current, but it do also interfere with the termination. The charger terminates to early.

Temp2898

M1: 30,9C, M2: 31,6C, M3: 33,8C, HS1: 35,9C
It stays very cool during charge.

Temp2900

M1: 31,8C, M2: 32,3C, M3: 31,2C, M4: 34,9C, HS1: 37,0C

ML202%20load%20voltage%20sweep

Here is a look at the charge current at different voltages.

PowerOn

The charger do not have any computer chip inside, this makes it start immediately.



USB output


ML202%20(PA18650-31)%20%231%20load%20sweep
ML202%20(PA18650-31)%20%232%20load%20sweep

With one battery it can supply 1A output current, but as can be seen below not for long.

ML202%20(2xPA18650-31)%20load%20sweep

With two batt the current can reach 1.25A, but it will not terminate on overload anymore.

ML202%20(2xPA18650-31)%20charging%20load%20sweep

The usb output will also work when usb input power is connected and it maintains full usb output voltage.

10ohm

There is 17mV rms and 156mVpp noise. This is very good values.

5ohm

There is 30mV rms and 220mVpp noise.

5ohmDual

There is 24mV rms and 170mVpp noise. Using two batteries will reduce the noise slight.



Tear down

DSC_3556

To look inside the box four screws must be removed.

DSC_3557

It looks very symmetrical, but each channels is not completely separate. The usb output is controlled from U5, it handles two inductors, but is a single channel boost controller.


DSC_3558

There is nothing on this side of the circuit board.



Conclusion

The design makes it fairly handy for a power bank (Dedicated power banks is usual smaller) and it can also easily be used as a 18650 charger.
It works fairly well, but as my test shows there are a few details that could be better.



Notes


The charger was supplied by Gearbest 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/charger