A closer look at Marstek’s 5 kWh plug-in battery

Marstek Energy brought its 3 kW, 5 kWh Venus E 4.0 residential storage system to Solar & Storage Live UK, Birmingham, where pv magazine took a closer look at the plug-in solution.

The system combines 5,024 Wh of lithium iron phosphate (LiFePO4) battery storage with 3 kVA grid-connected charging and discharging capability. It can also provide 3 kVA of off-grid output and deliver up to 3.6 kVA of peak backup power for 10 seconds, allowing homeowners to maintain essential loads during power outages.

Marstek Energy claims a cycle life exceeding 10,000 cycles at 25 C, with an 88% depth of discharge and efficiency above 90% across the battery and AC cycle.

According to Daisy Jiang, key account manager at Marstek Energy, the company believes the 5 kWh model is particularly well suited to British households.

“The Venus E series has already arrived in the UK through our local distribution network. Our initial focus is on the Venus E 5 kWh system, which we believe is a strong fit for the market,” Jiang said.

Designed for outdoor deployment, the Venus E 4.0 carries an IP65 rating and operates in temperatures ranging from -20 C to +60 C. The battery measures 520 mm x 430 mm x 191.2 mm, weighs 47.2 kg and uses natural convection cooling rather than active fans. Protection specifications include DC II and AC III overvoltage protection categories.

The battery supports Bluetooth, Wi-Fi, LAN, RS485, MQTT and cloud-to-cloud communications. According to Marstek Energy, these capabilities are intended to support integration with energy management systems and dynamic tariff platforms, an increasingly important feature in the UK residential storage market.

“We are currently working on deeper integration with Octopus Energy and other energy management providers,” Jiang said. “This allows homeowners to optimize battery charging and discharging around dynamic electricity pricing and maximize the value of flexible tariffs.”

Scalability is another feature of the platform. While the base unit offers 5 kWh of storage, Marstek Energy says the Venus E platform can be expanded through parallel operation to provide up to 15 kWh of storage capacity and 9 kW of power output using its SmartBox solution.

The Venus E range forms part of a wider strategy that has already seen the manufacturer establish positions in several European markets. Jiang said the company has achieved significant penetration in Germany, France, Poland, Ukraine and the Benelux countries through its plug-in storage products.

While plug-and-play batteries have gained traction across mainland Europe, UK regulations for plug-in solar introduced in August did not include plug-in battery products. The UK government has since launched a tender for a technical risk and safety assessment of plug-in battery products to inform future regulations.

“The deployment of plug-in battery products is currently influenced by UK regulations, which do not yet fully accommodate this type of solution,” Jiang said.

“While the regulatory environment for plug-in batteries is moving more slowly in the UK than in some European markets, we continue to see strong long-term potential,” she added. “Once UK regulations evolve to accommodate plug-in battery systems more fully, we believe the market will expand rapidly.”

Marstek Energy argues that its vertically integrated manufacturing model helps differentiate it in an increasingly crowded residential storage market. The company manufactures key system components in-house, including battery cells, inverters, battery management systems and software.

“Our biggest differentiator is vertical integration,” Jiang said. “Because we control the entire product stack, we can manage costs effectively while maintaining product quality and performance.”

In addition to the 5 kWh Venus E Gen 4.0, Marstek Energy’s full plug-in battery range includes the 2 kWh Venus E Mini, and 10 kWh Venus E Max.