There’s no right size for a USB battery pack, but it’s my deeply held belief that if you’re only going to buy one battery, it should be 10,000mAh.
That’s enough juice for at least two full phone charges, and probably closer to three, but it’s still small enough to carry with you in most situations. I’ve never fully drained a 10,000mAh pack, but I have killed a 5,000mAh, and my brain has been reshaped and bruised by the smartphone era to the point that that experience—a dead backup battery pack—weighed me down with a frankly shameful amount of anxiety. If you feel the same way, you could seek counseling, or you could buy a bigger battery, and the battery is a lot cheaper.
Enter Anker’s new PowerCore Lite 10000 and PowerCore Redux. Both are 10,000 mAh battery packs with a single PowerIQ USB output port that maxes out at 12W, or the same as a standard iPad charger. Both also include a unique trickle charge mode that allows them to be used with low-draw devices like Bluetooth headphones, which often don’t demand enough power to keep USB battery packs “awake.” Specs-wise, the only difference is that the Lite has an optional USB-C input port, in addition to microUSB, so you can recharge with two different types of cables. Sadly, you can only use the USB-C port to recharge the battery, not to charge your other gadgets with the battery, but even so, its omission from the Redux may disqualify it immediately for many of you.
Basically, the PowerCore Lite is what you would get if you ran over the Redux with a rolling pin. It’s only one ounce heavier (7.4 vs. 6.4) despite that additional port, and is roughly the size and shape of an iPhone X. The Redux is quite a bit thicker, but with a much smaller footprint, and usually a smaller price tag too. There are no wrong answers here, so when choosing between the two, I’d simply think about where and how you’re going to keep the battery. Back pocket? laptop sleeve? Go with the Lite. Loose-ish front pocket? Backpack? I think Redux is overall a better use of space, and feels a lot more comfortable to hold in your hand.
Of course, we can’t fail to mention the tried-and-true PowerCore II 10000, Anker’s older 10,000mAh mainstay. Size-wise, it’s closer to the Redux than the Lite (though a bit larger and heavier, overall), and has a faster PowerIQ 2.0 port that supports Quick Charge 2.0 for compatible Android phones, but lacks the handy trickle charge feature of its new siblings, and the USB-C input of the Lite. I tend to think that trickle charging is more useful than Quick Charge in a battery—you can charge any phone with the Redux and Lite, but you can’t charge certain smaller products with the PowerCore II—but I’m also an iPhone owner, so it’s not really for me.