Did some messing around and as someone said below, it seems to throttle as it gets closer to 80. Plugged it in at 49 for 4 minutes and it jumped 7%.

Haha fair

Fair but 1% in 5 minutes on a 30w charger is particularly slow, no? That suggests it would take 8 hours to charge on a fast charger.

Fair. Will try again when the battery dies more and report back.