Wireless Airpod charging issue

I wanted to know how long does it typically take to charge your Airpods wirelessly? Mine for some reason take 6+ hours to fully charge. I noticed the battery life went from ~50% to 81% in over 2.5 hours. This doesn't seem right. I've also tested it when the battery was lower, as devices usually charge faster when the battery is lower. I set the case on the wireless charger, making sure it the light on the case flashed, when the case was at 8% and left it on the charger for about 30 minutes. When I came back to check the status — it was still at 8%. I then proceeded to test the charger with my iPhone and it went from 74% to 77% in about 5ish minutes. So, I don't believe the charger is defective. Any thoughts?

Thank you!