Stronta ST135-BESS 35kVA Battery Energy Storage System

The Stronta ST135-BESS is a 135kVA / 260kWh battery energy storage system (BESS) designed for grid-constrained, off-grid and hybrid power sites in New Zealand.

It combines lithium iron phosphate (LFP) batteries, an integrated power conversion system, a built-in energy management system and genset control in one rugged, plug-and-play enclosure.

It can boost the power available from an existing site supply, run a site on battery alone, work alongside a diesel generator forming a hybrid system to cut fuel use and run hours, or store energy from solar.

The ST135-BESS is supplied and supported by OMC Power Equipment from Christchurch and Auckland. It is part of the Stronta Power Solutions range and pairs naturally with Stronta diesel generators.

This product can be configured with Powerlocks, Cee-form Connectors, or Hardwire Connections

What is the Stronta ST135-BESS used for?

Grid-constrained sites: more power without the network upgrade

It's a familiar story. A sawmill, factory or processing plant invests in a new piece of equipment, then finds out it needs more power than the site supply or local transformer can deliver.

The lines company comes back with a quote for a network upgrade that can run into six figures, with a lead time measured in months and sometimes years.

The ST135-BESS offers a faster, more flexible alternative. The battery recharges from the site's existing three-phase supply during lighter-load periods, then delivers stored energy when the new equipment is running, shaving demand peaks the supply couldn't handle on its own.

The result is far more available power at the point of use than the existing connection could deliver alone. For many sites it can defer or avoid a costly upgrade, and because the unit is transportable, it can move with the business if operations change.

Noise-sensitive sites, events and film shoots

With near-silent operation and no exhaust fumes while running on battery, the ST135-BESS suits locations where a running generator simply isn't acceptable:

• Events and festivals: quiet power for stages, food vendors, lighting and front-of-house areas.
• Film and television shoots: clean, quiet power on set, without generator noise ruining takes or long cable runs to a distant genset.
• Urban and residential work: night works, inner-city construction and sites with consent conditions on noise.

Construction sites and site compounds

The ST135-BESS can run offices, lighting and tools on battery overnight and during light-load periods, with the generator only starting when it's actually needed.

Hybrid generator systems

Paired with a diesel genset, the engine runs at an efficient load to charge the battery and then shuts down. That means less fuel, fewer run hours and longer service intervals.

Off-grid and remote sites

It suits farms, rural infrastructure and remote facilities that need dependable power without a grid connection, or may have existing solar.

Solar integration

PV connects directly to the unit, so daytime solar can be stored for use at night.

How does it work with a diesel generator?

The ST135-BESS includes a genset control interface that can automatically start and stop a connected generator based on battery state and site demand.

When the battery runs low, or the load rises beyond what the battery should carry alone, the generator starts, supplies the site and recharges the battery at the same time.

Once the battery is charged, the generator shuts down and the site returns to quiet battery power. A diesel generator is most efficient at a solid load.

This hybrid approach avoids the fuel waste, wet stacking and extra wear that come from running a generator lightly loaded for long hours.

Key features

• Liquid-cooled LFP battery. Lithium iron phosphate is one of the safest and longest-lasting battery chemistries available. Liquid cooling and heating keep the cells at a stable temperature, and active cell balancing helps protect capacity over a long service life.
• Built for real site loads. The inverter handles fully unbalanced three-phase loads and non-linear loads such as rectifiers, chargers and drives. Its overload capacity covers motor starts and short peaks.
• Uptime-focused energy management. The onboard EMS manages the battery, grid or generator supply and solar as a single microgrid, prioritising continuous power to the site.
• Plug-and-play setup. Power conversion, battery, EMS and control are integrated in one enclosure, which means simpler transport, faster installation and less on-site integration.
• Remote monitoring. Cloud monitoring over Ethernet or 4G/5G shows battery state, load and generator activity from anywhere. A large local touchscreen serves on-site operators.

Built tough, ready for hire

The ST135-BESS is built for life on the move. Its robust IP54-rated enclosure protects the batteries, power electronics and cooling system from dust and splashing water, and critical components are sealed to a higher rating.

The fully self-contained, plug-and-play design is well suited to rental and hire fleets, where units are transported, deployed and redeployed between sites. Remote monitoring lets hire companies and site managers keep an eye on battery state, load and usage from anywhere.

Standards and compliance

The ST135-BESS power conversion system complies with AS/NZS 4777.2, alongside international safety and EMC standards for the inverter and battery pack.

The system is designed in accordance with IEC 62933 and UL 9540 and carries UN 38.3 and UN 3536 transport certification. Full details are on the spec sheet.

Why choose Stronta from OMC Power Equipment?

Stronta Power Solutions is OMC Power Equipment's own New Zealand brand, backed by a local team with years of experience in generator sizing, hybrid systems and site power.

We can size a BESS, generator or grid-supported solution for your load profile, supply complete hybrid packages, and support you with commissioning, servicing and remote monitoring across the North and South Islands.