Battery Builder

Each cell is a Duracell-style AA: 1.5 V, ~0.15 Ω internal resistance, 2.5 Ah capacity. Stacking cells vertically in one column puts them in series (voltage adds, capacity stays 2.5 Ah). Adding cells in other columns connects those series strings in parallel (voltage unchanged, capacity adds). A grid of m rows × n columns is an mS · nP battery: EMF = 1.5·(upright − flipped) V per column, internal resistance = (0.15·m)/n, capacity = 2.5·n Ah. The bulb is the load — brighter means more power delivered. Double-click (or right-click) a cell on the rack to flip it 180° — an upside-down cell contributes −1.5 V, so a 3-cell column with two upright and one flipped cell gives 2·1.5 − 1.5 = 1.5 V. Columns wired in parallel are averaged — so a +1.5 V string in parallel with a −1.5 V string cancels to 0 V (real batteries require parallel strings to share equal voltage; here the tool averages them so you can watch cancellation).