Why a Containerised Battery System Skips the VFD

What the BESS integrator needed

A North American OEM needed a BESS container cooling fan moving 24,892 m3/h for a containerised battery energy storage system.

Their supply was 460V three-phase at 60Hz, standard for industrial equipment in that market.

Why the airflow figure is that high

Battery modules generate substantial heat, and failing to remove it costs more than efficiency. Cell temperature drives ageing. Beyond a point, it drives safety.

So a BESS container cooling fan is a safety component in a system where thermal management is the entire risk profile.

• A 460V, 60Hz three-phase supply.
• Next, variable speed control, so airflow follows measured cell temperature.
• Meanwhile 0-10V and RS485 communication with their management system.
• Finally, continuous duty across a wide ambient range, since containers ship worldwide.

Specifying the BESS container cooling fan

The airflow requirement pointed at the 800mm series at once. However, the interesting decision was the motor.

The AC option and why it lost

Certainly an AC motor would reach the airflow easily, and cost less to buy.

However, the customer needs variable speed. An AC motor cannot modulate without a separate variable frequency drive, and that drive is a cabinet-mounted box with its own heat, its own wiring and its own failure modes.

Inside a sealed container in a remote location, every additional box is somewhere a fault can occur that nobody will reach quickly. Consequently we ruled it out.

What an integrated EC motor removes

Instead this BESS container cooling fan carries the control intelligence inside the motor. It takes 0-10V or RS485 straight from the battery management system, with no drive between.

Consequently a component disappears, along with its wiring, its enclosure space and its heat. On a container where space and serviceability are both tight, those add up to more than the price difference.

Tuning for the actual pressure

A BESS container runs at low to medium static pressure, since the air path is short and mostly open. That is a different problem from pushing through a dense heat exchanger.

So the five-blade impeller is tuned for maximum airflow at low back-pressure rather than for pressure. Furthermore it uses a high-strength plastic composite, keeping rotor weight down at 800mm.

What it cost

Noise and purchase price. At 78 dB(A) this fan is loud, and an EC motor costs more than an AC one before the drive is counted.

Noise is inherent to moving 24,892 m3/h. Meanwhile the price gap narrows once the VFD, its enclosure space and its installation join the AC side, although it does not vanish. In short, anyone comparing on fan price alone reaches the wrong answer.

Technical Specifications

Note the voltage range row below. Spanning 380 to 480V lets one BESS container cooling fan serve both European and North American sites.

Technical Documentation

Here the full technical specification sheet contains performance curves, wiring diagrams, and installation warnings for system integrators. Open Full Technical Specification (PDF).

The product image and dimensional drawing provides exact measurements for OEM product designers integrating the fan into their chassis.

If you are cooling a battery container

A BESS container cooling fan has a specific failure profile. So these matter more than the airflow number.

• Compare system cost, not fan cost. An AC fan plus a VFD, its enclosure space, its wiring and its commissioning is the honest comparison against an integrated EC fan. Fan price alone consistently favours the option that costs more installed.
• Count the boxes inside the container. Every separate component is a fault that needs a site visit. On remote installations, reducing part count is worth real money in service cost, not just in assembly time.
• Get fan status back to the battery management system. RS485 gives you speed, current and fault state rather than just an on signal. In a system where thermal runaway is the risk being managed, knowing a fan is degrading matters more than knowing it has power.
• Specify the voltage range, not the nominal. A fan rated 380 to 480V serves both European and North American sites from one part number. That is one qualification, one spare and one supply chain instead of two.

See our axial fan range, the EC axial fan section, or battery cooling fans. Ingress ratings follow IEC 60529.

Questions about this fan

Is an EC fan really cheaper than AC plus a drive?

Installed, usually yes, although not on the fan line of the quotation. Add the drive, its enclosure space, the wiring and the commissioning time, and the gap closes or reverses. So compare the two as complete solutions rather than as components.

What does RS485 give beyond 0-10V?

Feedback rather than just command. You get actual speed, current draw and fault status, so your management system can tell a healthy fan from one that is slowing. On a battery system, early warning of a cooling fault is worth considerably more than the wiring it costs.

Is 78 dB(A) a problem for a containerised system?

Usually not, since these sit on industrial or utility sites rather than near occupied buildings. That figure is at full speed too, which the fan reaches only at high ambient or full battery load. Where a site has a noise limit, the speed control is what keeps you inside it.

Why not a fan optimized for higher pressure?

Because the air path in a container is short and mostly open, so high pressure capability buys nothing. A fan tuned for pressure moves less air at low back-pressure than one tuned for flow. Matching the impeller to the actual system curve is what gets you the airflow per watt.