The Amazon Echo Dot is a neat device and pretty portable, except that it doesn't have a battery and it takes a minute or so to reboot if you unplug it from one place and plug it in another.
I've used a li-ion powerbank pack attached to the Dot for a year now. Very convenient to be able to carry the Echo Dot to another room to continue listening to a podcast. But to do that, it has to remain plugged in to the charger full time. Recently I noticed that the rectangular package had popped apart. Apparently the Li-Ion cells swelled under continuous charge. Not confidence building. So, what I really need is a rig where the Dot can be running on AC power, I plug in a battery before unplugging the AC supply, carry it to my destination, and then either plug into AC again or continue running on battery for as long as it lasts. And then I recharge the battery separately. I'm sure such a thing is possible electronically but I've never seen one. An OTG octopus might work but I'm not sure.
To be explicit, I think I need something that has a micro-USB output (which goes into the Dot) and two micro-usb inputs. One input would be for the battery pack and the other for output from a wall wart. And I need to be able to plug and unplug either one (though obviously not both) without resetting the Dot or shorting out the power supplies.