Battery terms — the industrial battery glossary

Ampere-hour (Ah)

The unit of battery capacity: one ampere flowing for one hour. Always read it with its rate (see C-rate) — the same battery delivers fewer Ah when discharged faster.

AGM (Absorbent Glass Mat)

A sealed (VRLA) construction holding the electrolyte in a glass-fibre mat pressed against the plates. Strong at high-rate discharge; happiest in air-conditioned float duty. See 2V AGM cells.

Boost / equalising charge

A deliberate, controlled overcharge at elevated voltage that returns all cells to full charge and stirs the electrolyte in flooded batteries. Skipping it is how tall cells quietly stratify and sulfate.

C-rate (C5, C10, C20)

The discharge duration a capacity figure belongs to: C5 means capacity over five hours, C10 over ten, C20 over twenty. Slower rates flatter the number — compare batteries only at the same rate, and for motive duty insist on C5.

Capacity test (discharge test)

The only proof of capacity: a controlled full discharge at a stated rate to a stated end voltage. Everything else — voltage, impedance, appearance — is inference.

Cell reversal

What happens when one weak cell in a string is driven backwards by its stronger neighbours during deep discharge — a killer of neglected multi-cell batteries.

Charge return

The ampere-hours put back during recharge expressed against the ampere-hours taken out — flooded batteries need modestly more than 100% to finish the chemistry and stir the acid.

Cycle / cycle life

One discharge and recharge = one cycle; cycle life = how many the battery delivers before capacity falls to a defined limit — always stated with the depth of discharge and temperature, or it’s a slogan.

Depth of discharge (DoD)

How much of the capacity is taken out per cycle, as a percentage. Life and DoD trade against each other — the shallower the daily bite, the longer the battery lives.

Electrolyte

Dilute sulphuric acid — in lead-acid batteries it is an active material, not just a conductor: its concentration falls on discharge and returns on charge, which is why specific gravity reads state of charge.

Equalisation — see Boost charge

Same discipline, different name on some datasheets.

Float charge / float voltage

The continuous low-level charge that keeps a standby battery full for years. Held at the maker’s specified voltage with temperature compensation — the single most important setting in a battery room.

Formation

The factory electrochemical process that turns cured plates into living active material. Not the same as charging — a distinction that matters more than most datasheets admit.

Gassing

Electrolysis of water into hydrogen and oxygen near the end of charge in flooded cells — some is inherent and useful (it stirs the acid); excess wastes water and ventilation. Charger discipline decides which you get.

Gauntlet / PT bag

The woven tube that holds a tubular plate’s positive active material around its spine; a PT (pluri-tubular) bag is the full row woven as one fabric. Our founder patented it in 1975 — the story is here.

Gel battery

A sealed (VRLA) construction with the electrolyte immobilised in silica gel — immune to stratification, self-limiting in water loss, the remote-site workhorse. See OPzV.

Impedance / conductance testing

A quick electrical health check useful for TRENDING a battery over time. It cannot verify capacity — treat a single reading as a hint, a trend as information, and a discharge test as proof.

Intercell connector

The conductor joining cell to cell — rated, torqued and inspected, because a battery is only as strong as its weakest joint.

Monobloc

Several cells factory-built into one container (6V, 8V, 12V blocks) — fewer connections, easier installation, the standard format for golf cart and smaller traction batteries.

OPzS

The DIN designation for flooded stationary cells with tubular positive plates — the utility world’s long-life standard. See our OPzS range.

OPzV

The sealed sibling: tubular plates in gel electrolyte, valve-regulated — OPzS longevity for places nobody visits. See our OPzV range.

Opportunity charging

Topping up a working battery during breaks instead of full recharges. Engineered deliberately it can serve multi-shift fleets; done casually it shortens battery life dramatically — declare it before you buy, not after.

Plante cell

The oldest stationary construction — pure-lead formed plates. Venerable, bulky and costly; largely superseded by tubular technology, though the name survives in legacy specifications. See the modern replacement.

Specific gravity (SG)

The electrolyte’s density relative to water — in flooded cells, a direct window on state of charge. Read correctly (eye level, correct meniscus, temperature noted) it is honest; read casually it misleads.

Spine

The cast lead-alloy rod at the heart of each tube in a tubular plate — the current collector whose slow corrosion usually defines the battery’s true end of life.

Stratification

The layering of strong acid at the bottom of tall flooded cells when charging never stirs them — a quiet capacity thief cured by proper boost/equalise discipline, and designed out entirely in gel batteries.

Sulfation

Lead sulfate crystals hardening on chronically undercharged or long-idle plates until recharge can no longer reclaim them. Prevention is charging discipline; cure, past a point, is replacement.

Tubular plate

The deep-cycle positive-plate construction: active material packed around spines inside woven gauntlets, so cycling cannot shed it. The full engineering story: tubular plate technology.

VRLA (Valve-Regulated Lead-Acid)

The sealed family — AGM and gel — where recombination replaces watering and a one-way valve guards the pressure. “Maintenance-free” means no watering; it never means no care.

Watering (topping up)

Replacing the water electrolysis consumes in flooded cells — with demineralised water only, at the END of charge, never before. The cheapest life-extension in the industry.