| Word | Description |
| 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. |
| HCA | hot-cranking amps |
| HD | heavy duty |
| 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. |
| Hz | hertz |