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#11
My tablets and phone use 5V DC 2.0A input from the AC adapter [except one that needs 2.5A to charge] so a portable power pack as mentioned would need that much output along with the MicroUSB plug to fit. Look at the AC adapter, should have that DC figure printed on it, probably required by law.
My Raspberry Pi's all use a micro USB for power like smart phones. The Intent was so you could use your phones power pack as a power supply. Most of mine are 2 or 2.5 Amps. I should have taken the time to look it up but I was thinking something like a Surface tablet would likely have a barrel jack for power. My bad. I looked at a couple of USB Battery Packs and the stated output is 1A, that may not be enough? It would be iffy on just my Pi 3B. I did see one with a 2A output though. Just be careful which one you buy, if you go that route. The higher the mAh rating the longer it will last run time wise.