HCA - hot-cranking amps.

HD - heavy duty.

Hz - hertz.

Hazardous Waste - Waste that is classified by the government as potentially harmful to the environment. Lead and cadmium are examples of chemicals that are particularly hazardous.

Heavy-Duty Battery (Commercial) - A lead-acid, liquid-electrolyte, starting battery used in medium and heavy-duty trucks, construction vehicles and other off-road vehicles.

Heavy-Duty Battery (Dry-Cell) - A dry-cell battery used in low-to-medium-drain applications, such as flashlights and radios. A lower-priced alternative to an alkaline battery, it has less capacity and is unsuitable for high-drain applications.

Hertz (Hz) - A unit of frequency equal to one cycle per second.

Hot-Cranking Amps (HCA) - A rating similar to CCA that is used to define the current output of a storage battery at 80°F (27°C). These inflated ratings should not be confused with CCA.

Hourly Rate - See amp-hour.

Hydrometer - An instrument — normally a mechanical float type device but can be electronic — used to determine the state of charge of a battery by measuring the specific gravity of its electrolyte.