How to qualify a battery supplier

A battery supplier is qualified on evidence rather than on a quotation: the UN 38.3 test summary, the product standard report, a quality management certificate and one named engineer who answers technical questions. Price comes later, because a cheap pack that cannot be shipped or cannot be repeated costs more than a dearer one that arrives on time. The method below runs in about a week. Write the specification first, shortlist on capability, ask for documents that name numbers, then buy a small quantity before you commit to a year of production.

2026-08-05

## What do you need to define before you contact anyone?

Your specification, in writing, before the first email goes out. Cell chemistry or a performance envelope, nominal voltage and capacity, charge and discharge current, expected cycle life, operating temperature range, form factor and enclosure, the battery management system (BMS) functions you need, the standards your customer will insist on, the annual volume and the date you need first units. If you cannot answer half of that list, the factory will answer it for you. Their answers will suit their production line rather than your product.

## How do you build a shortlist?

On capability and geography, before anything else. Work out first if the job needs a cell maker, a pack builder or both, since those are different businesses with different economics and different minimum volumes. Then filter by country, because it sets your logistics, your working language and how easy an audit visit is. Four to six names is the right size for a first round. Fewer than three gives you no comparison. More than eight and you will not do the work properly on any of them.

## Which documents should you ask for?

Ask early, in the first exchange. Treat what arrives as the real answer, because a company that cannot produce a document in two weeks will not produce it under deadline pressure either. Four requests do most of the work. The UN 38.3 test summary for the exact design you intend to buy. The product standard report, meaning IEC 62133-2 where the product is portable and IEC 62619 where it is installed or industrial. The quality management certificate, with its number and the body that issued it, so you can check it instead of believing it. Then the scope of any customer audit the plant has already been through.

## What does a supplier audit actually check?

Whether the plant can repeat what it did once. Look at incoming inspection of cells, at how they are stored and graded, at traceability from cell batch to finished pack serial, at the rules for rework and at what happens to a pack that fails final test. Ask to see one real non-conformance record, closed, with the corrective action written on it. If nobody can show you one, either nothing has ever gone wrong in that building or nothing gets written down. Both answers tell you something.

## How do you validate before you commit?

Buy a small quantity and test it yourself. Run capacity and a short cycle check against your own specification rather than against the datasheet. Take one unit apart. Look at the cell brand and the date codes inside, at the welds, at the wiring discipline and at whether the BMS firmware version is documented anywhere. Then order a second small batch from a different production week. Compare the two. Consistency between batches is the thing you are actually buying and it is the only property a first sample cannot show you.

## Which terms decide the relationship?

Lead time, minimum order quantity, tooling ownership, price breaks and what happens when a cell goes end of life. Lead times in this industry are quoted in weeks and they move with cell availability, so put the quoted figure in the contract with a remedy attached rather than leaving it in an email. Settle who owns the tooling and the design files before the first payment leaves. Agree in writing what happens if the cell you qualified is discontinued, because that clause decides whether requalification is at your cost or theirs.

## What should make you walk away?

A datasheet that no engineer will stand behind on a call. A test summary describing a different configuration from the one you are quoted. A refusal to name the cell maker. A price that moves more than the specification does between two quotes. None of these is proof of anything on its own. Two of them together, in a first conversation, is a pattern worth acting on before you have spent anything.

## What this directory can and cannot tell you

This site lists companies, shows where each record came from and prints the date it was checked. That is the whole of it. It is not an assessment of anybody's compliance, it does not verify anybody's quality system and it is not a substitute for your own audit. For test work, use the battery testing labs category and speak to a laboratory directly. For a conformity assessment question, the notified body or certification body named by your customer is the authority, not a directory and not a vendor blog.