Yeah, the battery pack operates at 5V x 10000 mAh, which is roughly 50 Wh. That puts it well udner the 100 Wh that IATA has in its guidelines.

I've always been very up front about it with airline and security personnel, and they've always said it's fine as carry-on. I suppose if I tried to carry a bunch of them it might be a problem, mind you.

Loose batteries that are unprotected are a big no-no. Spare battery packs and chargers in reasonable quantities under the personal limit are generally fine. Check the fine print if in doubt.