I recently bought a Baseus PicoGo AM52 10,000mAh Qi2.2 power bank, which is advertised as supporting 25W wireless charging on the iPhone 17 Pro Max.

I’m starting to wonder if my unit may be defective because the charging speeds seem unusually slow for 25W.

I did a controlled indoor test today. iPhone 17 Pro Max, official Apple FineWoven MagSafe case, Wi-Fi, mostly listening to podcasts (which were actually paused for much of the test), and only occasional light phone use.

These were my results:  
09:30 — 21%  
10:00 — 55%  
10:30 — 80%  
10:45 — still 80%  
10:49 — 81%  
11:00 — 87%  
11:37 — 100% (possibly reached a few minutes earlier)

So 21% to 80% took exactly one hour, and 21% to 100% took roughly two hours.  
The strange part is that it basically stalled at 80% for around 15–20 minutes. My charge limit is set to 100%, Battery settings only said “Charging”, and the phone wasn’t being used at that point. The power bank was hot earlier in the session, but not too hot to touch.

I also previously tested it outdoors and the performance was even worse: 22% to 80% took around 1h28.  
What makes me suspicious is that my Belkin 25W Qi2.2 desk charger is roughly twice as fast in similar conditions. I understand a battery pack may perform worse than a mains-powered charger because of efficiency and thermals, but this still seems like a huge difference.  
The AM52 isn’t exactly cheap, so I’m trying to work out whether this is normal thermal throttling for this power bank or whether I should return/exchange my unit.  
Has anyone here tested the AM52 with an iPhone 17 Pro Max? Do these charging times look normal to you, or would you suspect a defective unit?

Baseus PicoGo AM52 Qi2.2 25W charging unusually slow on iPhone 17 Pro Max