I was at a show today, it was the second day of a two day event. Trade stands were doing a roaring trade.
One was running a professional version of Paypal on a laptop. But the person running the stall said: "I am sorry, I can only take orders for cheque or cash, no plastic cards, as the battery in my laptop is about to give out and I do not want it to go off line during a transaction."
Why not carry a (fully charged!) spare battery or take a power supply with you?
I do not understand how some people can survive in business...