I was riding next to a gal yesertday that I met on a paved trail. She was on a 3yo Brompton 3 fold with a Swytch kit and was at minimal assistance trekking along at about 15mph. She said she get's about 25 miles on one charge. Hers is 3 yrs old; don't know tech on battery size. But she was telling me they are changing batteries on new ones to small batteries. Looking at it today they are coming out with two battery sizes, with four different capcities. So the "Air" which would fit the Brompton, comes in 90wh (they advertise 10 miles), 180wh, They say (20 miles) 280wh and 370wh. I know miles is a estimate. But the 90wh one is within carry on (100wh) limit). United Airlines site says passenger can carry on two Li Batteries, max 100wh and total not to exceed 180wh. So Bike would go in check luggage and battery in carry on. What I wonder about - if anyone knows... is it possible to fly international USA/UK and get a battery in UK from swytch dealer that will work with USA bike? In US extra battery for 90wh is $135. I realize electronics are different - on charging battery packs... but could a UK "battery pack" be used on a US bike with US charger with an invertor. Or? Could a USA battery be ordered but sent to a UK shop to pick up? Here is what I am thinking - would travel with bike and one small 90wh battery. P/u 2nd or bigger battery after arrival that would either have to be left there or sold there on departure. Be a lot cheaper then having to buy and sell a whole bike and could travel with my own bike. Anyone know? Or know a swytch dealer in the UK I could email to ask? Thanks for your thoughts.