BatteryScout Glossary — Car & Van Battery Terms Explained

Absorbent Glass Mat (AGM) batteries use a fiberglass mat separator that holds the electrolyte in place, making them spill-proof and vibration-resistant. AGM batteries are ideal for Start/Stop systems, vehicles with high electrical demands, and applications requiring deep cycling. They typically last longer than standard flooded batteries and can handle more charge/discharge cycles.

Enhanced Flooded Battery (EFB) is an improved version of traditional flooded batteries, designed specifically for Start/Stop systems. EFB batteries have enhanced cycling capabilities and better charge acceptance compared to standard batteries, but are less advanced than AGM. They're a cost-effective solution for entry-level Start/Stop vehicles.

Cold Cranking Amps (CCA) measures a battery's ability to start an engine in cold temperatures. Specifically, it's the number of amps a battery can deliver at 0°F (-18°C) for 30 seconds while maintaining at least 7.2 volts. Higher CCA ratings indicate better cold-weather starting performance, which is crucial in winter climates.

State of Charge (SoC) represents the percentage of available battery capacity remaining, typically measured as a percentage from 0% (fully discharged) to 100% (fully charged). A healthy battery at rest should show 12.6V-12.8V, which corresponds to approximately 100% SoC. Monitoring SoC helps prevent deep discharge and extends battery life.

A condition where a battery is discharged below 50% of its capacity, typically below 12.0 volts. Deep discharge can cause permanent damage through sulphation, where lead sulfate crystals harden on the battery plates and reduce capacity. Repeated deep discharges significantly shorten battery life. Smart chargers with reconditioning modes can sometimes recover lightly sulphated batteries.

Parasitic drain (also called parasitic draw) is the continuous electrical current consumed by vehicle systems when the engine is off, such as alarm systems, clocks, memory modules, and keyless entry receivers. Normal parasitic drain is typically 20-50mA. Excessive drain (over 100mA) can flatten a battery overnight and indicates a fault that needs diagnosis.

The alternator is a critical component that converts mechanical energy from the engine into electrical energy to charge the battery and power electrical systems while the engine runs. A healthy alternator should output 13.7V-14.7V when the engine is running. Worn alternators or loose belts can prevent proper battery charging, leading to premature battery failure.

A diagnostic tool used to assess battery health by measuring voltage, internal resistance, and sometimes performing load tests. Modern battery testers can determine State of Charge, State of Health, and Cold Cranking Amp capacity. Professional-grade testers provide more accurate readings than simple voltmeters and help distinguish between flat and dead batteries.

An intelligent battery charger that automatically adjusts charging current and voltage based on battery condition and chemistry type (AGM, EFB, or standard). Smart chargers typically include multiple charging stages (bulk, absorption, float) and can recover deeply discharged batteries. They're safer and more effective than basic trickle chargers and help extend battery life.

A simple, low-amperage battery charger designed to maintain battery charge over extended periods, typically used for vehicles in storage or seasonal use. Unlike smart chargers, trickle chargers provide constant low current and can overcharge batteries if left connected too long. Modern trickle chargers often include automatic shutoff to prevent damage.

An automatic engine management system that shuts off the engine when the vehicle comes to a stop (e.g., at traffic lights) and restarts it when the driver releases the brake or engages the clutch. This system reduces fuel consumption and emissions but requires batteries with enhanced cycling capabilities, typically EFB or AGM technology.

The starter motor is an electric motor that cranks the engine to start it. It draws significant current (often 100-300 amps) from the battery during cranking. A failing starter motor can draw excessive current, causing voltage drops that prevent starting even with a healthy battery. Symptoms include slow cranking, clicking sounds, or no response when turning the key.