Why a Battery Conductivity Tester Belongs in Every Toolbox?

Batteries rarely announce their retirement date. One week they crank the engine or keep the cameras rolling; the next, they quietly fade and leave you scrambling for a backup. A pocket-sized closes that guessing window. By shooting a low-voltage signal through the cells and reading the internal resistance, it tells you—in seconds—whether a battery is still fit for service or ready for...