Market is flooded with various types of batteries. They vary in brand name or popular shouts like ‘Plus’, ‘Ultra’, ‘Super’. But in most cases not a word about their real capacity. Practically it is hard to decide if price is reasonable for one or another battery. All we care is the real juice stored in them. So Denis bought a bunch of batteries available on market and started battery capacity measuring project.
The idea is simple and not new. Circuit simply discharges battery and keeps track of its voltage and current. We already know that Arduino is great for such setup. To make things more precise he also used a temperature sensor to track ambient temperature which is one of a major factors affecting battery capacity. Arduino already has an USB so there is a logging capability added. To discharge battery he simply used 5.5Ω resistor where Arduino using ADC reads voltage across it. Denis whole circuit in to nice enclosure with battery socket, attached LCD where energy, capacity, voltage, temperature and time is seen. Using logging he found out Cost per Wh of commonly used batteries. Using this information it is easier to decide what batteries to purchase for your needs.