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.
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.
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)
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.
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.
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.
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.
