How to Choose a BESS Enclosure Supplier: Six Checks Before You Order

To choose a BESS enclosure supplier, check six things before you order: whether it designs the racks around your battery pack and issues the envelope drawing with the quotation; what its enclosure-level factory acceptance test (FAT) covers; which management and factory approvals it holds; how many enclosures it builds a year and has delivered in one batch; whether the enclosure width ships as a standard container; and whether you can audit the factory and inspect before shipment.

Settle first what you are buying: the enclosure only, a battery-ready enclosure, or one with liquid cooling, fire protection and LV systems fitted in the factory. What to send with your request for quotation is in the BESS enclosure RFQ checklist.

1. Can it design around your battery pack?

Ask whether the supplier sends a rack-and-pack envelope drawing with the quotation: usable pack width, height and depth, the load limit per shelf, the cooling connection points and the pack fixing positions. Your pack supplier designs to that drawing, so the racks are not reworked at assembly.

Racks are best designed and built by the enclosure maker to the pack dimensions and anchoring loads, so that enclosure, racks and coolant piping fit together. Liquid cooling normally runs up to the connection on each pack: chiller, distribution manifold, hoses and quick couplings, and flow balancing across the racks; the cold plates and the coolant circuit inside the pack stay with the pack supplier. Deflagration venting, gas detection and the emergency exhaust interlock are configured per project and local code.

ETENZ designs and builds its battery racks in-house and issues the rack-and-pack envelope drawing with the quotation.

2. What does its factory acceptance test cover?

An enclosure-level FAT should cover the structure and lifting points, a water spray or jet test to the agreed IP rating, a pressure and leak test of the liquid-cooling loop with the chiller running, fire-protection interlocks, LV circuits and earthing. Each item needs a record, issued with the delivery documentation.

On a batch order, build a first unit, review it, then release the batch, so that issues are fixed on unit one. The 72 enclosures for the China Three Gorges Haixi high-voltage direct-connected storage project were delivered in batches after the first unit passed review.

System tests after the packs are installed, such as charge and discharge, are carried out on site by the system integrator.

3. Which approvals does it hold?

At enclosure level, a supplier can show management system certification, factory approval and container approval:

• ISO ⁠9001, ISO ⁠14001 and ISO ⁠45001 certification;
• factory approval from a classification society;
• type approval of the 20 ft high-cube design, CSC included, so enclosures of that design ship as standard containers;
• for European projects, an EU declaration of conformity for the electrical equipment fitted in the enclosure.

ETENZ holds ISO ⁠9001, ISO ⁠14001 and ISO ⁠45001 certification and factory approval from the American Bureau of Shipping (ABS). Its 20 ft high-cube design has RINA type approval, CSC included, for a maximum gross mass of 50 t.

UL ⁠9540 lists the complete storage system, UL ⁠9540A is a fire test report that the battery or system supplier obtains, and NFPA ⁠855 and local permitting apply to the whole installation. The system supplier handles these; the enclosure supplier supports them with enclosure drawings and technical documents.

4. How many does it build, and in what batches?

Ask three things: how many enclosures the plant builds a year; how many of one type it has delivered in a single batch, and how long that took; and whether the whole batch was built to one set of drawings and one process baseline.

ETENZ builds more than 5,000 electrical equipment housings and prefabricated enclosures a year. For the grid-forming storage project in Zhongwei, Ningxia, it built 143 enclosures of the 20 ft, 5 MWh class to one set of drawings and one process baseline, from the start of production to the last delivery in 40 days.

5. Does the width ship as a standard container?

A 2,438 mm wide enclosure has the ISO standard width and, with a CSC plate, is booked as a standard container. A 2,550 mm wide enclosure is booked as out-of-gauge cargo at sea, and some countries treat it as oversize on the road. Fix the width before you ask for freight quotes.

6. Can you see the factory?

On a factory audit, look at the welds and lifting points, coating thickness and adhesion, the IP water test, the enclosure-level FAT records and, if there is one, the first unit.

ETENZ welcomes factory audits, and buyers can inspect the enclosures at the plant before shipment.

How ETENZ answers the six checks

ETENZ builds more than 5,000 electrical equipment housings and prefabricated enclosures a year at a 70,000 m² site in Fengxian, Shanghai. It holds ISO ⁠9001, ISO ⁠14001 and ISO ⁠45001 certification and ABS factory approval, and its 20 ft high-cube design has RINA type approval (CSC included, 50 t maximum gross mass). The rack-and-pack envelope drawing comes with the quotation, and the enclosure-level FAT runs before shipment, with the records in the delivery documentation.

ETENZ builds BESS enclosures for battery makers and storage integrators, to the buyer's drawings or battery-ready: see BESS enclosure manufacturing for OEMs and integrators and the full range of BESS enclosures.

Frequently asked questions

Which documents are usually needed for vendor registration?

A business licence, ISO ⁠9001, ISO ⁠14001 and ISO ⁠45001 certificates, classification-society factory approval and a list of delivered projects. ETENZ can provide all of these.

Does a BESS enclosure need its own certification?

At enclosure level the approvals cover the container and the factory: a standard-size enclosure with a CSC plate ships as a standard container, and in European projects the electrical equipment in the enclosure carries an EU declaration of conformity. UL ⁠9540 listing, UL ⁠9540A reports and local permitting cover the complete storage system and are handled by the system supplier.

Can buyers inspect the enclosures before shipment?

Yes. Factory audits are welcome, and you can inspect the enclosures at the plant before shipment.

What comes with the delivery documentation?

Drawings, the bill of materials, the enclosure-level FAT records and the certificate of conformity; in European projects, also the EU declaration of conformity for the electrical equipment in the enclosure.