This won’t fully charge a 13 pro max but it is great in a pinch when you are out and about without access to a plug. It gives you that extra 40% or so to get you home. It is heavy and obtrusive though. I actually only use it around to house. I keep it on at home so I know when I leave the house the phone will be at least 90%. One thing to keep in mind is that when it’s not plugged in it only charges at 5w. On full brightness and during heavy activity it’s just about enough to keep the phone from discharging but sometimes you will see a little battery drop in these situations. Once you are done with the processor intensive task it goes back to slow charging. Great accessory if you have reasonable expectations. There are more powerful and versatile offerings out there but none tie into IOS like this one.