Battery energy storage for sites

What a site battery does

A battery energy storage system (BESS) is a battery, an inverter, cooling, protection and controls in one enclosure. It connects between a source of power and the equipment that uses it.

That position is the whole point. The source, whether a grid connection or a generator, can deliver energy at a steady rate. The site rarely uses it at a steady rate. A crane lifts for seconds and waits for minutes. Cabins draw a little overnight. A pump starts and the demand jumps.

Without storage, the source has to be big enough for the largest moment. With storage, the source can be sized nearer the average, and the battery supplies the difference.

The three arrangements

Almost every site battery works in one of three ways. Which one fits depends on what is available to charge it.

Grid + battery

A connection charges the battery and the battery supplies the site. This suits sites where a connection exists but is too small for the peaks.

Read more about limited grid site power.

Generator + battery

The generator runs for part of the day, at a sensible load, to charge the battery and help with heavy demand. The battery supplies the site the rest of the time.

Read more about hybrid generator + battery systems.

Battery-only, for a defined duty

The battery supplies a known load for a known time, then recharges from a verified source.

Power and energy are two separate questions

Buyers used to generators think in one number: the kVA rating. A battery needs two.

• Power, in kW and kVA, is how much the system can deliver at once. It has to cover your largest sustained load, with short peaks inside its overload ratings.
• Energy, in kWh, is how much it stores. Together with your load, it decides how long the system runs between charges.

A system can have ample power and too little energy for a long shift, or plenty of energy and too little power for a large motor start. Both have to fit. The guide to kW, kVA and kWh works through examples.

The systems we specify around

Our current range centres on two mobile battery systems made by Ampd Energy. These are substantial industrial units: the Ampd 200 has a nominal output of 193 kW / 214 kVA and the Ampd 400 386 kW / 428 kVA, with 215 kWh and 430 kWh of rated nominal DC capacity.

Each unit also has higher overload ratings for short periods, which is what makes them relevant to cranes and motor starting. Those figures are time-limited, and nominal DC capacity is not the same as usable energy at the output. The product pages set out every figure with its source.

Where a battery fits well, and where it does not

A battery tends to fit well where:

• the load is peaky, such as tower cranes and hoists;
• a generator runs for long hours at low load;
• a grid connection is smaller than the peak demand;
• there are set periods when an engine cannot run.

It fits less well where the load is high and steady all day with no time to recharge, where the project is very short, or where the load is far smaller than the available units. In those cases a correctly sized generator, or a better connection, may be the right answer. A proper assessment should be willing to say so.

How to specify one

You do not need an electrical specification to start. You need to be able to describe:

1. What needs power. The equipment, or simply the generator you use today.
2. What can charge the battery. A connection and its capacity, a generator, or neither yet.
3. How the site operates. Working hours, the busiest periods, any quiet periods.
4. Where and when. Country, start date, duration, and whether you expect to hire or buy.

The site power assessment collects exactly this, accepts “not sure” for any technical answer, and gives you a summary to keep. The guide to what to include in a BESS quote covers the detail an engineer will ask for next.

Product figures on this page: Ampd 200 Brochure IEC Rev 1.3, dated 29 April 2026; Ampd 400 Brochure IEC Rev 1.3, dated 29 April 2026. Manufacturer-published, not independently tested.