Can I take portable chargers on airplanes?

Yes, but with rules: power banks must be in carry on luggage (never checked bags). Under 100Wh (roughly 27,000mAh at 3.7V) is allowed without airline approval. 100 160Wh requires airline approval. Over 160Wh is prohibited. Most consumer power banks (10,000 20,000mAh) are well under the limit. The mAh rating on the device must be visible unmarked batteries may be confiscated.