Last year in Portugal, a friend's six-year-old daughter, who understands that I do not speak much Portuguese, showed me a toy that requires batteries. She opened the back and I think she said "não tem pilhas, as coisas para aqui chama pilhas". When I look in the dictionary, I usually find that the word for battery is bateria but I also see that pilha means cell. When do you say bateria and when do you say pilhas? Muito obrigado.