What do you mean, like does the charge reach to 100% in an hour? No, it charges very slowly.
Someone that charges by the hour: You pay the person for each hour worked. Usually they try to work as much hours as possible to charge (as in, receive money) more.
It's a pun on words... charge it to the creditcard / charge a battery / charge as in "attack".
Allow me to lend a machete to your intellectual thicket...
Captain Jack Sparrow