I love the PB2 but the inability to charge low drain devices is a bummer. If I had known that before hand I would have never bought it. Oh well, it charges the wifes cell phone when she is out and about for the day and it does charge a few particular 18650’s quickly. Other than that, it’s useless.
PB2 will turn off when output is lower than (I think) around 300mA. So charging the smartphone is fine as it has high current for fast charging, but some devices use low current (for low capacity battery) and it will not work with PB2 as power bank… Deal breaker for me too, I would have two PB2s already at home if it does not do this…
Does it feature independent charging? Meaning the 2 batteries are in parallel or separate? (what I mean is, if they are in parallel, then it may not be good to charge 2 different capacity batteries or 2 batteries in different state of charge (different voltage when first placed inside that powerbank)…
The Xtar PB2 has independent charging. I believe many of the Tomo (2/3/4-bay) powerbank/charger models also have independent charging.
An inherent problem with removable cell power banks is contact resistances (springs, contact themselves and etc). They pose an efficiency and to some extent cut-off hurdle which increases with current draw.
Power bank circuitry works much better when batteries are soldered (low temp solder solutions available) or spot welded.