Charging with a power bank

ethan.gerardot wrote:

My main concern is about damaging the battery. I'm not asking if it will actually charge...I'm wondering if it's safe for the iPhone (i.e. will it damage the battery or not).

There shouldn't be a problem. An iPhone 8 is fully capable of up to 2.1 A input with a USB-A power supply. As long as the supply is well regulated to 5V, it's shouldn't matter what it's capable of putting out. It's the power management circuitry inside the phone that handles all the charging, and it determines the input current. You could have something that could put out infinite current at 5V and it would be safe because the device itself limits the input current. Of course if the power supply is current limited (like a 1A Apple cube power adapter) the device will just deal with what it can get.

This is basic Ohm's Law, which is V = I x R or I = V ÷ R. This is why one can plug in a nightlight pulling 0.05A into and outlet that can safely supply 15A.

Hello,

Yes, most any charger will work if the cable is compatible:

Charge your iPhone with an iPad or Mac notebook power adapter

However, if you are using non-Apple products, see this:

Identify counterfeit or uncertified Lightning connector accessories

Good luck.

Just as a follow up, if you really want more maximum power coming out of a power supply, it might take a combination of a bigger size and active cooling. I found this, which is 100A (500 watts) at 5V. I think it's designed for desktop computers. It apparently has a fan to keep it cool. However, if you could connect it to a USB plug as an experiment, it should work just fine as long as the power output is clean.

https://www.amazon.com/RSP-750-5-Power-Supply-Single-OUT-17-Pin/dp/B00YJVFRUE

It’s completely safe (assuming that it’s a quality adaptor)

A power adaptor is fundamentally only a DC power source.

The actual “charger” is inside your device; it will only draw as much power as it needs from the adaptor.

The device “pulls” … the adaptor doesn’t “push.”

It’s not unlike your home … you may have 48,000 watts of power available from your utility, but your desk lamp still only “pulls” 50 watts.

ethan.gerardot wrote:

Thanks! That makes sense to me. But it makes me wonder...what's the point of a 1A apple cube power adapter? Why not just put out all 15A from the wall socket? (Since apparently the phone only draws what it needs)

Transformers or switched-mode (used by Apple OEM supplies) power supplies have to be properly sized for their output as they generate heat since they're not 100% efficient, and there are losses in the form of heat. It's simply not possible to safely run about 1500 watts DC output through something that small. It would probably overheat and catch on fire.

Size is typically scaled with power output. Also - a supply that can put out considerably more power may be less efficient if all the user needs is 2.1A. I don't see too many USB-A power adapters that have an output rating of more than 3A.

USB-C is a bit different though. It gets complicated since they all have to put out 5V but can put out other voltages. However, the 5V rating is typically for 3A or 15 watts.