Test/Review of Charger and power bank Miller ML202 V4

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.

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

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

Got it, thanks!

> 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.

> 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.

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)

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

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.

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.

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.

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

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.

Hey Everyone,

Can anyone confirm this behavior with their ml202?

I am powering a small mobile router from 2x18650 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!

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.

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: Pololu - TPS2113A Power Multiplexer Carrier with USB Micro-B Connector - 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.

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 x 18650 style charger and powerbank. Also looking at the Tomo M2 if anyone has compared them.

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

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

> the large inrush current that overloads the output circuit.

I know nothing about electronics. Isn’t that the kind of problem managed by putting a capacitor in the circuit, to slow the inrush or outrush?