How to choose correct mAh powerbank?

[AC Question]

What mAh power bank is safe for an LG G4 and (optionally) iPhone 5S? Is higher mAh just faster when charging (and therefore hotter too)? Or what does higher mAh indicate?

 

[LeoRex]

The mAh rating is basically just a capacity. The higher the number, the more times you can charge your device off a fully charged power bank. So a 10,000mah will be able to charge your 3000 mAh G4 about three times, whereas a 5000mAh bank will get you 1 full charge and a partial charge.

Most reputable power banks will be safe for pretty much any recent phone.

 

[Rukbat]

You normally don't want to discharge the phone lower than 40%, so you'll need a little more than 60% (you have to allow for the fact that charging and discharging a battery isn't 100% efficient) of the phone's battery capacity to recharge it fully.

Since the G4 battery is 3,000mAh, you'll discharge it to 1200mAh, meaning that you'll need to put back 1800mAh (plus losses, or about 2000mAh) per charge. Figuring the same inefficiency in the power bank, you want about 2200mAh per charge you'll need, and you don't want to discharge the power bank lower than 40% of its capacity either. Figure how many charges you want to get per charge of the power bank (you'll need smaller power bank to assure power through a long workday than for a week long trip in the mountains) by using only 60% of the power bank's capacity.

A power bank with larger capacity won't charge the phone any faster than one with a small capacity, and no size is "unsafe" (to your phone - a huge one may be dangerous to your wallet).

Consider mAh like volume of a container and charging rate like the size of the opening.in the container. A 200 gallon tank with a 1/16" pipe won't fill a gallon container very fast (the pipe size is the Amps the power bank can deliver - most of them can deliver 2.1 Amps, because phones don't draw more than that), but it will fill it 200 times. A 5 gallon tank with a 6" pipe will fill a 1 gallon container very fast, but only 5 times. (Another difference is that the phone can't "overflow" - charging stops at 100%, even if the charger or power bank is still connected.)

One other consideration is the construction. A power bank in a cheap plastic case won't last long unless you're very careful with it. (I've seen some that look so fragile I'm afraid to pick them up.) One in a solid aluminum block can be dropped - as long as you're not barefoot. You could break a toe with some of them.

 

[donmarkon]

10000 mAH (good battery not some fake) for me is nice compromise between size and practicality.