I always use a coin and idk how but sometimes it tightens way to much then when I do to loosen it I can't and I've actually broken the cap because of it
I'm not T1, never mind a pump user, but wanted to comment that no gadget is ever perfect.
A least with replaceable batteries you can always carry them with you. Recharging a gadget, unexpectedly isn't always that convenient, I'd think. For instance, yesterday I spent a couple of hours in an airport awaiting a flight. We then had a short delay, then a 9 hour flight, then drive to the house. Recharging could have been tricky for much of that day.
Of course, that's not a typical day for anyone really, but the same could be true of a day of meetings, a conference, power outages (rarely planned), travel delays of all manner. Then every now and then rechargeable batteries need to be replaced, or at least that has been my experience with gadgets.
I appreciate in some countries batteries are more expensive, per unit, than in UK, but surely, like most places, if you use a lot, you would be able to find a supplier from whom you can buy in bulk at a discounted rate?