Reference
Reference
This glossary explains in plain words the terms you meet on a battery label, in your vehicle's manual and when talking to a specialist. The terms are split into three groups: what a battery is made of, which specs describe it, and what happens to it over its service life.
A battery label looks like a set of cryptic markings until you learn what they stand for. After that, choosing a replacement and talking to a specialist get noticeably easier.
Design
- Cell
- A separate compartment inside the battery that produces about 2 V. In a lead-acid car battery, 6 cells are connected in series and together give the nominal 12 V.
- Electrolyte
- The liquid or soaked material inside the battery: a sulphuric acid solution. If it gets on your skin or in your eyes, rinse with plenty of water and seek medical help.
- Plates
- Lead grids coated with active material and immersed in the electrolyte. The chemical reactions that let the battery store and deliver energy take place on them.
- Polarity
- The position of the positive and negative terminals on the case. It can be standard or reversed; a replacement battery must match the layout your vehicle is designed for.
Specs
- Nominal voltage
- The nominal working voltage of a battery. For a lead-acid car battery it is 12 V, while a multimeter usually shows about 12.6–12.7 V on a fully charged, healthy battery at rest.
- Capacity
- A measure of how much charge the battery can store and deliver. It is shown on the label in amp-hours; take the right value from your vehicle's manual.
- Cold cranking amps
- The current a battery can briefly deliver to the starter, especially in the cold. It determines how reliably the engine starts, and the required level is set by the vehicle manufacturer.
- Size
- The case dimensions and mounting type. Even a battery with the right electrical specs is useless if it doesn't fit the battery tray or can't be secured properly.
Care
- Self-discharge
- The natural, gradual loss of charge even when nothing is connected to the battery. That is why a battery in long-term storage is checked and topped up from time to time.
- Deep discharge
- A state in which the battery has given up almost all its charge, for example after a night with the headlights left on. Ordinary starter batteries tolerate such episodes poorly, especially repeated ones.
- Sulphation
- A buildup of compounds on the plates that stops the battery accepting and delivering charge. It usually develops when a battery is left discharged for a long time; leave assessing its condition to a specialist.
- Parasitic drain
- Current drawn while parked beyond the normal level, due to a fault or incorrectly connected equipment. The sign is a battery that goes flat noticeably faster than usual; finding the cause is a job for a specialist.
Where these words come in handy
- Guides
How to charge a car battery at home: preparation, steps, mistakes and a checklist. The article catalogue is here too.
- Questions
Short answers on signs of a flat battery, charging at home, storage, replacement and recycling.
- Collections
Reading paths: getting ready for winter, a car left parked for weeks, choosing a new battery by its specs.
- Sections
Four sections: battery design and types, testing and charging, seasons and storage, safety.
Related pages
- Questions
Short answers on signs of a flat battery, charging at home, storage, replacement and recycling.
- Guides
How to charge a car battery at home: preparation, steps, mistakes and a checklist. The article catalogue is here too.
- Collections
Reading paths: getting ready for winter, a car left parked for weeks, choosing a new battery by its specs.
Sources
- Training materials on automotive electrical systems
- Vehicle owner's manuals
- Russian Federal Waste Classification Catalogue (FKKO)
Information is current as of the date the page was prepared. Batteries differ in design and maintenance requirements, so the final word always belongs to the manual for your vehicle, for the battery itself and for your charger.