A lead-acid battery in storage is not resting — it is slowly discharging itself, and how you store it decides how much battery is left on the day you finally install it. Batteries wait more than most people think: between factory and commissioning, between purchase and a delayed project, between seasons in a dealer’s stock. This guide covers that waiting — the shelf, not the service. If what you have is an in-service battery being parked for the cold months, that is a different job with its own guide: winter storage. If your question is about moving batteries — including whether they count as dangerous goods in transport — that belongs to the shipping guide.
What happens on the shelf
Every battery self-discharges: internal chemistry ticks over even with the terminals open, and capacity quietly walks out of the box. How fast depends on the design and, above all, on temperature — self-discharge is a chemical reaction, and like the others in the box it obeys the Arrhenius rule: heat accelerates it, cool slows it. The standard reference literature says it plainly: self-discharge proceeds at a lower rate at reduced temperatures, so cooler storage extends what arrives at commissioning day (Linden, Handbook of Batteries). The danger is not the lost charge itself — that can be put back — it is what a lead-acid battery does while it stands discharged: the plates begin to sulphate, and sulphation that is left to harden becomes capacity you do not get back. Stored charged, topped up on schedule, a battery waits gracefully. Stored flat, it ages faster standing still than it would have done working.
The rules of the room
The room itself is simple to get right. Cool, dry, ventilated, out of direct sun — the cooler end of the maker’s stated band, because every degree is Arrhenius working for you instead of against you. Batteries stand upright, never stacked cell-on-cell beyond what the packaging states, terminals protected against the accidental spanner or strap that turns a stored battery into a welder. Keep them clean and dry on top: a film of damp dust is a slow leakage path between terminals. And run the store as a store: first in, first out, receipt dates on the cells, so no battery grows old at the back of the rack while newer stock ships from the front. What the room must be for batteries in service — ventilation sizing, charging bays, eyewash — is the battery room guide’s subject; and the acid itself deserves the respect set out in the safety guide.
The refresh charge — storage’s one real duty
Storage is not a zero-maintenance state; it is a low-frequency maintenance state. The literature even has a name for the duty: the boost charge — “charging of batteries in storage to maintain their capacity and counter the effects” of standing (Linden, glossary). The discipline is more important than the ritual: the interval between refresh charges is set by the maker’s datasheet and shortens as the store gets warmer, so the honest routine is a log — receipt date, open-circuit checks, refresh-charge dates — kept per battery, not per room. A dealer or projects store that cannot show that log is not storing batteries; it is depreciating them. If a battery has been found deeply discharged in storage, do not guess it back to health: recover it deliberately, per the charging guide, and test before it ships.
Filled versus dry-charged — two different clocks
One distinction sets the whole schedule. A filled and formed battery — electrolyte in, charged at the works — is live chemistry from the day it leaves the factory: its shelf clock runs continuously, and the refresh-charge log above is its life-support paperwork. A dry-charged battery holds charged plates but no electrolyte; with the chemistry essentially suspended, it stores by a different, gentler clock — sealed as delivered, dry room, until the day it is filled and given its first charge. Which type you are holding is on the despatch papers, and the maker’s manual states each schedule. Either way, a battery that has waited long should not go straight to work on faith: commissioning exists precisely to prove what the waiting cost.
The storekeeper’s checklist
Received: date marked, damage inspected, papers filed. Stored: charged state, cool and dry, upright, terminals guarded, FIFO. Maintained: refresh charges on the maker’s interval, logged per battery. Released: oldest first, checked before despatch, commissioned before trusted. And one question worth asking any supplier, ourselves included: how long has this battery been in your store, and can I see its storage log? A maker with nothing to hide will show you the dates. If you are holding stock now and the log does not exist yet, start it today and ask us for the right refresh schedule for what you hold — it costs nothing to ask and a battery to guess.