How Many Battery Racks Fit in a 40ft BESS Container

2026-01-20

In a standard 40-foot Battery Energy Storage System (BESS) container, the number of battery racks typically ranges from about 8 to 24 or more. This depends on design choices such as energy capacity, battery type, cooling method, and other included components.

This answer is straightforward, but to understand why rack counts differ and what it means for system design, let’s explore the details.

40ft BESS Container

Table of Contents

Typical Battery Rack Counts in 40ft BESS

Depending on the manufacturer and energy capacity targets, these are common setups:

System Type / Capacity	Approx. Battery Racks	Notes
~1 MWh (Commercial)	~8 racks	Common for lower energy applications, often paired with PCS and auxiliary components.
~2–4 MWh	~12–18 racks	Balanced design for mid‑range utility and commercial use.
Up to ~6.5 MWh (Battery‑only)	~24 racks	Larger energy‑dense setups where container space is focused on batteries.
General industry guidance	~20 racks	Typical design referenced in a technical overview.

Why Is Quantity a Range?

Energy Capacity Goals
More racks generally mean more cells, resulting in higher total energy storage. A system aimed at 6+ MWh will need many more racks than one designed for 2 MWh or less.
Balance Between Batteries and Other Equipment
In fully integrated BESS containers (including batteries, PCS, transformers, EMS, and HVAC), there’s limited net space for rack rows. Containers focused mostly on batteries can host more racks.
Design Choices and Cooling
Air-cooled versus liquid-cooled rack designs affect spacing needs and how many racks can fit. Cooling systems, fire suppression, and cable routing also take up container volume.
Modularity and Expandability
Modular designs that allow for future growth will usually use a standardized rack count that can be expanded across multiple linked containers.

What’s Inside a Battery Rack?

Before going further, it's important to explain what “battery rack” means in a BESS context:

A rack is a frame that holds multiple battery modules or blocks.
Each rack has its own battery management (BMS) interfaces, safety disconnects, and connections to the DC busbar.
Racks are typically designed as parallel units that can scale energy capacity and redundancy.

For example, a 20-foot container from an industry datasheet showed 12 racks with 4 modules per rack as part of a 5 MWh solution.

Beyond the Rack Count: What Matters to Project Planning

Simply knowing the rack count doesn’t provide the full picture. Here are a few additional factors I’ve seen as a BESS design engineer:

Total Container Capacity

The amount of energy you want to deliver determines the rack count more than the container size itself. Two 40ft containers could each have 12 racks for a mid-range installation, or one could be battery-only with about 24 racks for a large utility project.

Rack Configuration

Each rack could hold different numbers of modules, and module designs vary in energy density, voltage, and shape.

Integration With Power Conversion Systems

Containers that include large power conversion systems (PCS), transformers, and Energy Management Technology (EMT) cabinets reduce the floor space available for racks.

Practical Considerations for Design and Operation

When planning a 40ft BESS container, these factors influence rack choices:

Cooling and Safety

Battery racks heat up during charge and discharge. Proper thermal management is crucial. More racks in a tight space require good airflow or liquid cooling designs, which may reduce usable rack space for safety reasons.

Maintenance Access

Designers often leave space between rack rows to allow technicians to service the system. While a compact, dense layout maximizes capacity, it may hinder maintenance.

Load Requirements

Having more smaller racks might provide better redundancy than fewer large ones. This is especially important in applications where uptime is critical.

Actual Cases

Here’s a snapshot from typical industry data:

A manufacturer’s 40ft container system with about 1.1 MWh capacity uses around 8 battery racks.
Some mid-range BESS products aiming for several MWh in a 40ft container often target 12–18 racks.
Battery-only container variants can utilize up to roughly 24 racks for very high energy capacity.

Potential Future Changes

Here are a couple of trends influencing the number of battery racks in future 40ft BESS containers:

Higher Energy Density Cells

As cell technology, like LiFePO4 and newer chemistries, improves, each rack can deliver more energy. This means achieving the same total capacity with fewer racks, or more capacity without increasing the number of racks.

Modular Multi-Container Systems

Large utility projects rarely rely on a single container; they connect multiple units in parallel. This approach standardizes and optimizes rack count per container for transport and ease of deployment.

Cooling Innovations

New cooling systems, such as more efficient liquid cooling, may allow for denser rack layouts without overheating issues, increasing the limits of what can fit in a 40ft footprint.

Summary

Typical battery rack counts in a 40ft BESS container generally range from 8 to 24 racks.
System design goals, including energy capacity and space for PCS and HVAC, as well as maintenance access, directly impact rack count.
Future trends in cell energy density and thermal management will continue to influence container configurations.

Understanding not just the number of racks but the reasons behind that number will help you make informed design decisions when planning a 40ft BESS container solution.