Test/Review of Charger and power bank Miller ML202 V4

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HKJ
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Test/Review of Charger and power bank Miller ML202 V4

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


  • Will discharge a battery with 1mA to 2.5mA when not powered.
  • When overdischarge protection trips the discharge current is below 0.03mA
  • Below 0.5 volt the charge current is uA.
  • Between 0.5V and 1.8V the charge current will is in the mA range (See curve).
  • Above 1.8 volt full charge current is used.

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: 30,9°C, M2: 31,6°C, M3: 33,8°C, HS1: 35,9°C
It stays very cool during charge.
Temp2900
M1: 31,8°C, M2: 32,3°C, M3: 31,2°C, M4: 34,9°C, HS1: 37,0°C
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

  • Can be used as UPS, will draw more power from the usb input.
  • Will discharge a battery with 1mA to 2.5mA when not powered.
  • When overdischarge protection trips the discharge current is below 0.03mA
  • When drawing usb power while charging, the power is taken from the usb input.
  • Usb output is coded as USB charger (DCP)

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

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

1dash1
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Thanks for the detailed review, HKJ!

Sounds like it is an adequate power bank and an adequate 18650 battery charger, with its main feature distinguishing itself from the competition being its relatively compact size and its main drawback being battery size limitation.

For those who are looking for a functional power bank/battery charger, this is a reasonably inexpensive option. Glasses

Rule 1-1 as it applies to life, take it as it comes.

swaan
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I have been waiting for a long time for this review. Thank you Smile

netprince
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Thanks for the review, I like the idea of these simple UPS style chargers.

Joat
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How separate are the two slots? Is it safe to have one fully charged cell and one discharged cell?

swaan
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Joat wrote:
How separate are the two slots? Is it safe to have one fully charged cell and one discharged cell?

Yes. Its like having 2x single slot chargers – only the output is combined. Undercharge protection, charging is separate.

will34
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Thanks for the review, I have this charger and I’m very happy with the performance, got 86% efficiency with 2x LGF1 18650s at 1A discharge rate.

Because it has LVP, when using a single cell you may not get all the energy from the battery, and often at 3.4V it will stop working. (because the voltage drops under load). The boost circuit doesn’t lower the output to reduce the current draw and keep the battery voltage above LVP like some more advanced powerbanks does. Like CV phase but for discharge.

swaan
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Can anyone confirm that it actually supports up to 18V input? Almost all sellers say that up to 18V is supported and 5-12V input is recommended.

swaan
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I decided to make my own short test:

  • I insterted 2 cells into ML202 V4. They were around 3.85V
  • It was measured with ZY1270 using serial output.
  • Notice that the amperage goes up with the voltage until around 5.3V (measured before the 0.5m USB cable)
  • At around 21.5V both red charging lights turned off! (it continued charging)
  • One of the red lights turned back on, later at around 5V. The other red light is not working properly anymore.
  • At the end cells were 4.02/4.03V
  • Despite one of the red LEDs acting weird it charges and discharges both sides OK.

Izombie
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It’s a power bank, but if it doesn’t have power applied, it discharges the battery slowly?
HKJ
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Izombie wrote:
It’s a power bank, but if it doesn’t have power applied, it discharges the battery slowly?

All power banks does that, the question is how slowly (Days, months or years). With easy replaceable batteries a few months are fine, as long as you do not store it with batteries in.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

swaan
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HKJ, could you please explain how can the ML-202 have separate charging and boost and then combine to one 5V? I thought you should never combine outputs like that.
I am thinking that if they can do it then perhaps I can somehow put 20 cells and 20 boost circuits for some 100W output?!

EDIT: I want to further clarify – I am thinking if I can somehow utilize half dead cells by putting a lot of them in parallel with protection circuits and use as a powerbank. So if some die (<2.5V), the output still works.

HKJ
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swaan wrote:
HKJ, could you please explain how can the ML-202 have separate charging and boost and then combine to one 5V? I thought you should never combine outputs like that.
I am thinking that if they can do it then perhaps I can somehow put 20 cells and 20 boost circuits for some 100W output?!

EDIT: I want to further clarify – I am thinking if I can somehow utilize half dead cells by putting a lot of them in parallel with protection circuits and use as a powerbank. So if some die (<2.5V), the output still works.

The ML202 do not combine outputs, but you can do it if you know what you do.
There are power banks that selective switches cell in, i.e. the cells do not have to be balanced.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

swaan
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I mean the 2 batteries are charged independently but there is a single USB output – what do you mean ML202 do not combine?

HKJ
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swaan wrote:
what do you mean ML202 do not combine?

It has one controller for the output, that means the two inductors are always in sync.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

swaan
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Got it, thanks!

hank
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> Can be used as UPS

How “uninterruptible” is it as a power supply — does it sustain the output when the input fails, is there a blink/loss of power as it changes over?

HKJ
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hank wrote:
> Can be used as UPS

How “uninterruptible” is it as a power supply — does it sustain the output when the input fails, is there a blink/loss of power as it changes over?

The usb output is always generated from the battery voltage, this means that there is no “change over” time.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

hank
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> up to 18v input

How about variations in input, from a solar panel — would it be usable by just attaching a solar cell, maybe for an outdoor light or camera to work unattended?

will34
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hank wrote:
> up to 18v input

How about variations in input, from a solar panel — would it be usable by just attaching a solar cell, maybe for an outdoor light or camera to work unattended?

Yes it does, I tried with input voltage up to 14V and it worked fine. Most 12V solar panels have much higher open circuit voltage (~20v) but once you attach the load it normalizes, swaan tested up to this voltage with no problem. Another feature is the pass-through charging which most normal powerbanks don’t have, really useful for using with solar.

hank
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Next question, tangential — what would be a suitably sized solar panel (to equip with a micro-USB output)
(how does this box behave with a solar panel once the cells are fully charged? does it switch off accepting electrons completely, so it doesn’t heat up?)

(I once boiled a 4-amp 12v lead-acid battery by leaving it directly connected to a 7” square 12v solar panel on a long summer day, so I’m cautious about overloading anything without an appropriate charge controller, which is another complexification)

HKJ
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gauss163 wrote:
Note that this implies that it will not work well as a UPS since it will be constantly draining and charging the battery.

That is no problem and will not even add any wear to the battery.

gauss163 wrote:
Further it the load drains it faster than it can recharge then it will eventually drain completely.

Yes, the purpose of a ups is to maintain the output. Turning the output off before the batteries are drained would be a fail for the ups.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

will34
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Self discharge is no problem with the ML202, after a couple weeks unused my battery still reads 4.12V. I have a “20W” solar panel and so far the amp draw seems to recover fine after voltage drops, but needs more extensive testing. The reason I say “20W” is because I could never get more than 6.5W from it even at full sun.

gauss163 wrote:
Most “UPS” functionality in powerbanks is poorly designed

If you’re referring to the lack of pass-through charging, I think they are actually better without it. Let’s say you connect the powerbank to a 5V 2A source and want to charge your phone at the same time, assuming the powerbank will draw full 2A and the phone draws 1.5A, you only get 0.5A remaining which is really slow. For all the heat generated and power lost in the process, you might as well connect the phone directly.

HKJ
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gauss163 wrote:
HKJ wrote:
gauss163 wrote:
Note that this implies that it will not work well as a UPS since it will be constantly draining and charging the battery.

That is no problem and will not even add any wear to the battery.

I’m not sure that we are talking about the same thing, but maybe we can figure that out if you explain why you think it will not add any wear to the battery.

You can start by explaining why it would constantly drain and charge the battery.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

HKJ
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gauss163 wrote:
HKJ wrote:
You can start by explaining why it would constantly drain and charge the battery.

I recall reading reviews of some devices that power from the cells but only begin charging once it drains to a certain level. Similar bad things can happen with variable loads which occasionally exceed the charging rate. How exactly does this device work in a way that you think it will not wear the cells?

And once it begins charging it will basically reach a equilibrium, not drain and charge the batteries constantly. I would expect a constant float charge on the battery and that will probably add some wear to it (The fact that is charger is slightly below 4.2 volt is an advantage here).
If the load is higher than the input level, then the batteries are supposed to boost the power.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

netprince
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Hey Everyone,

Can anyone confirm this behavior with their ml202?

I am powering a small mobile router from 2×18650 cells. After the cells are depleted, the router cuts off as it should. When I plug the ml202 in for charging, I get an alternating red and green flashing pattern. The cells are not charging and the USB output is disabled. I must then unplug the ml202, remove the batteries, re-install the batteries, and plug-in the ml202 before it will start charging again…

Makes this power bank not so usable for solar applications in my opinion… unless you manage to never deplete the batteries.

Thanks!

hank
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Can anyone say further on the points in the last 2 posts?
Is the chip Gauss describes as helpful being used in any power banks? Is the problem Gauss describes just slowly degrading the cell, or is the problem so bad it’s not worth using the charger as described?

And is the problem netprince describes related, and confirmed by anyone else as typical for this charger? OR is it just a defective one?

I think we’re at the point where there are so many chargers and solar panels on the market that it’s very hard to identify good setups.

swaan
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The problem of the power bank not restarting power output is due to the large inrush current that overloads the output circuit.

Some devices like phones soft-start charging so they are not a problem for the ML-202 but routers and single board computers like Raspberry Pi do not – so you will need something to soften the current draw from the power bank. If someone comes up with a plug and play solution let me know.

Right now my only idea is a power multiplexer something like this: https://www.pololu.com/product/2596 – the idea is that the computer draw power from the wall and will only switch to the powerbank when the mains power from the USB wall adapter is gone.

nquinn
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Could someone weigh one of these for me please without the battery and cable? Is 2.2oz accurate from gearbest?

I’m looking for an enclosed 2 × 18650 style charger and powerbank. Also looking at the Tomo M2 if anyone has compared them.

SkittleStoat
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Nice review, thanks. Does it have rubber feet to stop it sliding around?

swaan
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Its 52g + 9g for the lid. The feet are hard plastic.

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