A standard number in a specification is a promise about tests, not a promise about quality. Most weeks a tender line arrives reading “battery shall conform to IS 1651” or “as per IEC 60896”, and the same two questions follow: what does that fix, and does it make two batteries comparable? The honest answers are “less than you would hope” and “not automatically”. Here is the map, drawn from the documents themselves. One caution first: standards are revised, superseded and withdrawn. The editions named here are current as of 2026; verify with the issuing body before writing any of these numbers into a contract.
The Indian family, in one breath
The Bureau of Indian Standards publishes the lead-acid specifications through its Secondary Cells and Batteries Sectional Committee, and four numbers cover most industrial enquiries. IS 1651 governs stationary cells with tubular positive plates — the vented workhorse; its fourth revision, of December 2013, added parameters for Normal and High Discharge Performance cells and for cells in transparent SAN containers, plus tests for water loss, float suitability, short-circuit current and internal resistance. IS 1652 is its twin for Planté plates; the two were split out of one 1954 standard in 1960. IS 13369 covers stationary tubular batteries in monobloc containers. IS 15549 covers stationary valve-regulated batteries — the sealed, oxygen-recombination type described in our VRLA guide, which its scope defines as needing no topping up during their lifetime.
Underneath sit the ingredient standards almost nobody looks up — IS 15549’s own reference list names IS 266 for sulphuric acid, IS 1069 for water for storage batteries, IS 1146 for containers and IS 1885 Part 8 for the vocabulary. The acid and the water going into a cell are specified documents in their own right, which is why a battery filled with the wrong water fails in ways no handover test would catch.
The international family
For an export tender the numbers change but the structure does not. For stationary batteries, IEC 60896-11 covers vented types — general requirements and methods of tests — while IEC 60896-21 gives the methods of test for valve-regulated types and IEC 60896-22 gives their requirements. Note the split: one document tells the laboratory how to test, the other what counts as a pass. For motive power, IEC 60254-1 sets the general requirements and test methods while IEC 60254-2 fixes cell dimensions and polarity marking, so cells from different makers drop into the same truck compartment — what that means in practice is in our guide to traction batteries.
What a standard fixes — and what it deliberately does not
Read IS 1651’s scope and the boundary is plain: rated ampere-hour capacities, overall dimensions, performance requirements and tests. Now read its foreword, which records something most buyers would never guess — the first revision widened the capacity range and deleted the details about the inner construction of cells. The committee stepped back from prescribing how a cell is built. Everything separating a fifteen-year cell from a five-year one — spine alloy, casting quality, gauntlet, oxide, paste density, purity of the lead — sits outside the specification you are quoting. Conformance makes two cells interchangeable. It does not make them equal.
The rating basis, where comparisons quietly die
Here is the trap that costs buyers real money. A capacity figure means nothing without the conditions attached, and each standard attaches different ones. IS 1651 rates at the ten-hour rate, ending at 1.85 V per cell for Normal and High Discharge Performance types (1.80 V for transparent-container types), corrected to 27 °C. IS 15549 designates the rated capacity C10, ends at 1.75 V per cell, and also corrects to 27 °C. IEC 60254-1, for traction, rates at the five-hour rate to 1.70 V per cell. Three documents, three end-points — and one physical cell will publish three different ampere-hour figures, every one honest. (Those are end-of-discharge voltages, not charging settings; this article publishes no charging voltages.) Compare the rate, the end voltage and the reference temperature before the ampere-hours — our C-rate guide shows how far apart they drift.
The clause that settles most first-year arguments
Every battery maker fields the same angry call: the new bank was discharge-tested at commissioning and came in under rating. The standards anticipated that decades ago. IS 15549 requires the actual capacity, corrected to 27 °C, to be not less than 85 percent of rated in the first cycle, with rated capacity met within five cycles. IS 1651 sets the same 85 percent floor, with rated capacity reached inside the supplier’s stated number of cycles, to a maximum of ten discharges. A lead-acid battery is not fully formed the day it ships. IS 15549 caps the other end at 120 percent, because over-delivery signals a mis-declared rating as surely as under-delivery. Plan the cycles into any acceptance test and put the clause in the contract; our guide to testing a battery covers the discharge test itself.
Type tests, acceptance tests, and what a “lot” means
These two phrases are used interchangeably in tenders. They are not. IS 15549 defines type tests as those carried out to prove conformity with the standard, intended to prove the general quality and design of a given battery — one design, tested once, often years ago. Acceptance tests are carried out on samples drawn from a lot — and a lot, in IS 1651’s words, is all batteries of the same type, design and rating from the same factory, period, process and materials. A type-test report proves the design was capable; only an acceptance test says anything about the batteries on your delivery note. Ask for both, and ask who witnessed each. Nor are these abstractions: IS 15549 prescribes a wicking test on AGM separators and an oxygen-recombination-efficiency measurement. Somebody either ran them or did not.
What no standard will tell you
No standard can tell you how long a battery will last in your room, on your duty — that is what sizing and honest engineering are for. Nor whether the maker held the specification the day your batteries were built. And a quotation line reading “manufactured to IS 1651” is a claim, not a certificate. The certificate is a test report — named laboratory, named edition, named lot. Ask in that form, and check the edition is in force. If a specification has landed on your desk, send it to our engineers — we will tell you what it fixes, what it leaves open, and whether it is even the right standard for your duty, including the times the answer is that it is not.