Which quality step matters most in storage battery production?

Burn-in testing. Assembled packs run full charge and discharge cycles to simulate real use, which exposes cold solder joints, weak cell matching, and wrong BMS parameters. After burn-in, each unit gets a manual re-check before it can ship. Skip burn-in or sample only a fraction and the failures surface in the customer's hands.

What is the difference between laser and resistance spot welding?

Laser welding has a smaller heat-affected zone and produces consistent, solid joints, which suits temperature-sensitive cell terminals. Resistance spot welding is more prone to cold joints. A cold joint often passes initial testing, then resistance rises and the joint heats up in service, which is a common cause of early battery failure.

Inside an ESS Production Line: From Cell Intake to Burn-In and Shipment

A walkthrough of a storage pack line: incoming cell inspection, laser spot welding, enclosure assembly with BMS, two full burn-in cycles, and manual re-inspection. Plus the questions to ask your contract manufacturer.

When a customer asks whether we actually manufacture, promising is a weak answer. Walking the line is a better one. This video follows our storage pack line from cell intake to packed shipment, five stations in total.

Station 1: Incoming cell inspection

We use first-tier domestic cells, and they do not go straight onto the line when they arrive. Each batch is inspected: internal resistance, voltage, and physical condition. Only cells that pass go into storage.

It looks like a simple step, but it is where pack quality starts. If incoming cells are poorly matched, no amount of careful grouping or welding later will give the pack a long life.

Station 2: Laser spot welding

Cells are fixed in their designed layout, then welded. We use laser spot welding, which gives solid joints with a small heat-affected zone.

Why not resistance spot welding? Resistance welding is more prone to cold joints, and a cold joint often passes outgoing tests. Months later in the field, resistance climbs at that joint and it heats up. This kind of early failure is the hardest to attribute. Laser welding costs more and removes a category of warranty claim.

Station 3: Enclosure assembly and wiring

After welding, the pack goes into its enclosure for wiring, fixing, and BMS installation. Units ship with a Jikong active-balancing BMS as standard, handling centralised monitoring.

The difference between active and passive balancing shows up over years. Passive balancing burns off excess energy from high cells as heat through resistors. Active balancing moves energy between cells. Cell matching degrades with age, and active balancing slows that decline appreciably.

Station 4: Two full burn-in cycles

Every assembled pack runs complete burn-in cycles, and we run two rounds. The point is to simulate real operating conditions and force latent problems out early.

What does burn-in catch? Cold joints, weak cell matching, wrong BMS parameters, and damage left during assembly. All of these look normal in a static test and only appear under load and cycling.

Burn-in is not the end. Quality control then re-inspects each unit by hand. Nothing ships until every reading passes.

Station 5: Shipment

We take on storage product contract manufacturing and OEM/ODM customisation, mainly serving domestic traders and overseas Chinese customers, with volume shipment supported.

What to ask when you audit a line

If you visit a factory, three questions are worth asking after this walkthrough.

How many burn-in rounds, and how long? A factory that samples a fraction is not in the same class as one that cycles every unit.

Is the BMS actively or passively balanced, and can parameters be adjusted for your application?

Which cell brand and which batch, and is there an incoming inspection record? A supplier who cannot name the batch usually does not buy its own cells.

Where this stops

A standard line does not guarantee your custom requirement gets met. Unusual dimensions, special communication protocols, or non-standard certifications depend on whether the engineering team can support them. That is not something the production line itself can answer.

FAQ

Which quality step matters most in storage battery production?
Burn-in testing. Assembled packs run full charge and discharge cycles to simulate real use, which exposes cold solder joints, weak cell matching, and wrong BMS parameters. After burn-in, each unit gets a manual re-check before it can ship. Skip burn-in or sample only a fraction and the failures surface in the customer's hands.
What is the difference between laser and resistance spot welding?
Laser welding has a smaller heat-affected zone and produces consistent, solid joints, which suits temperature-sensitive cell terminals. Resistance spot welding is more prone to cold joints. A cold joint often passes initial testing, then resistance rises and the joint heats up in service, which is a common cause of early battery failure.

Want the factory walkthrough video or a quote? Contact us with your application and our engineers will spec a system.