I'm going on a long flight soon, and as my N900 is music player, and there are no power points in economy, I bought a 20,000 mAh power bank. It's quite snazzy, and works well.

Weirdly though, not with my N900. I plug it in, the power bank detects it, the N900 doesn't start charging, so the power bank switches itself off again. I've tried with normal USB cables and charging ones with no data lines. Same behaviour...the N900 just doesn't seem to draw any current, so the bank switches off.

Any thoughts/ideas?