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.
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.