Nineteen pre-service and in-service teachers taking a chemistry teaching methods course at a university in Hong Kong were asked to take a diagnostic assessment. It consisted of seven multiple-choice questions about the chemistry of the lead-acid battery. Analysis of the teachers' responses to the questions indicated that they had difficulty in solving problems regarding the recharging reaction at the anode, the direction of electron flow when recharging the battery, and the role of sulfuric acid. A class discussion was conducted to identify the teachers' misconceptions about the chemistry of lead-acid battery. A laboratory experiment was also carried out to help teachers dispel their misconceptions. (Contains 3 tables and 2 figures.)