What Actually Ships in a 100kWh to 1MWh C&I Battery System

Most first-time C&I buyers picture one cabinet arriving on a truck. What turns up is closer to six categories of hardware from as many places, and the project slips in the seams between them — a PCS that cannot talk to the BMS, a room with no suppression, a container that will not fit through the gate. Below is the delivery, category by category.

1. Battery racks

The core, and the only part most people price. Standard modules are 48V or 51.2V LiFePO4, commonly 100Ah, 280Ah or 314Ah. Each module carries a slave BMS; a master controller sits above the group. Parallel counts are limited by the BMS and by busbar current — the practical ceiling for a single group is typically around 16 units, which is why larger systems are built as several groups rather than one long string.

Two numbers matter and get confused constantly: nominal capacity on the label, and usable capacity after depth-of-discharge. A 300kWh nominal LiFePO4 bank delivers roughly 270kWh usable at 90% DoD. Quote on usable.

2. PCS — the inverter

Sized to your peak demand window, not to total site load. A plant drawing 800kW that spikes to 1,100kW for two hours needs a PCS covering that 300kW delta, not 1,100kW. Pairing is a compatibility question, not just a power question: the PCS must speak the BMS protocol. CAN and RS485 are the usual languages, and a mismatch here is the most common commissioning failure we see.

3. EMS and communications

The energy management system is where the savings actually come from. It decides when to charge from solar or off-peak grid, when to discharge into the peak window, and when to hold for backup. It has to reach the battery BMS, the PCS, and usually the site meter or SCADA — Modbus TCP or RTU into the plant network, plus CAN or RS485 down to the packs.

A battery with no EMS is an expensive standby generator that never decides to run.

4. Fire suppression and environment

Above roughly 100kWh, most jurisdictions require detection and suppression for a dedicated battery room or enclosure. Aerosol or clean-agent gas units are typical, wired to a gas detector and to the BMS so the system can isolate on alarm. Container systems add thermal management — the enclosure has to hold cell temperature in both a hot afternoon and a cold night, or cycle life suffers.

This line item is routinely missing from battery-only quotations, and it is the one the fire authority asks about.

5. Balance of system

Cables and busbars sized to actual current, DC breakers and isolators, earthing, and where the site voltage differs, a transformer. Boring, cheap relative to the battery, and the most common cause of a commissioning delayed email. Confirm whether your quote includes it.

6. Shipping and site readiness

Batteries ship as Class 9 dangerous goods. A valid UN38.3 test summary for the exact model, correct Class 9 labelling and a dangerous-goods declaration are mandatory; a summary that names the wrong model is the most frequent reason a container is held. On site, check door widths, floor loading and forklift access before the truck is booked, not after.

Worked example: a 300kWh build

Indicative configuration for discussion, not a specification. Final build depends on tariff structure, load profile and local code.

Frequently asked questions

Can I start at 100kWh and expand to 500kWh later?

Modular rack systems are designed for it, and expanding in the first couple of years is usually straightforward. Plan the switchgear and room space for the end state, because those are expensive to redo.

Rack or container?

Rack for anything that fits indoors and under roughly 500kWh. Container when you are out of plant-room space, above 500kWh, or the site is outdoor and remote. Container adds civil work and a longer schedule.

How long does commissioning take?

Rack systems often energise within days of delivery once the room is ready. Container projects run weeks longer because of civil work, interconnection approval and fire authority sign-off.

Related: how to source C&I storage from a manufacturer · C&I sizing and cost guide · rack-mounted battery modules