Abstract: For use in an automatic electric battery charger, a charge controller which monitors the rate of rise of battery voltage, and terminates the charge when the rate of rise falls below a predetermined value, typically 11 mV per cell in 45 minutes for a lead-acid battery. The battery voltage is monitored by combining with it a ramp signal which changes, in the opposite sense to the rise in battery voltage, at a rate just sufficient to offset a rise in battery voltage of the said predetermined value. In the preferred embodiment, the combining step is performed by a summing amplifier, and a bias signal is also fed to the summing amplifier; this bias signal is shifted, in one direction only, to hold the output of the amplifier between narrow limits as long as the rate of rise of battery voltage is greater than the predetermined value.