< img height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=693716185752290&ev=PageView&noscript=1" />
All News

Pytes V5°announces UL9540 certification with Sol-Ark inverters.

Feb. 2024

 Now, we are proud to announce the V5°, the updated version of our product, which is more powerful and secure, having proudly completed stringent testing and evaluation processes. It has also received UL9540 certification, coupled with Sol-Ark inverters.


UL 9540 certification is a crucial safety standard for energy storage systems (ESS) and related equipment in North America. It encompasses comprehensive safety considerations for the entire system, including the battery system itself, containment, functionality, fire detection and suppression, and environmental performance of the ESS. The acquisition of UL 9540 certification validates the safety and dependability of Pytes' energy storage system, showcasing its adherence to industry safety benchmarks.


UL 9540 represents a safety standard targeted at energy storage systems. When it comes to energy storage systems connected to a utility grid, the UL 9540 standard extends to the equipment utilized to establish that connection. This standard addresses fire and explosion safety concerns associated with ESS, encompassing aspects such as:

• The operational safety of the storage (battery) component

• Fire detection

• Fire propagation and suppression

• The effectiveness of fire mitigation in enclosed areas

As an ESS comprises multiple components, the UL 9540 standard actually consolidates two other older standards: UL 1973 (for the stationary battery pack) and UL 1741 (for the inverter). These two individual standards, alongside rigorous thermal and electrical testing and evaluation of the components working collectively as a system, collectively form the UL 9540 certification.



While UL 9540 represents a set of standards an energy storage system must adhere to, UL 9540A offers a method for evaluating thermal runaway propagation within an ESS. Therefore, while UL 9540A is not a certification in itself, it furnishes vital data for manufacturers seeking certification for their ESS products under UL 9540, and for their engineers and product developers to verify the product’s effectiveness in protecting against critical hazards like fire.

The UL9540A test method encompasses four stages:


Cell testing – Assessing cells for flammability, potential thermal runaway, and the composition of released gases.

Module testing – Evaluating the ability of thermal runaway to propagate from one cell to others within groups or "modules," as well as outside the module.

Unit testing – Analyzing the potential for fire to spread from unit to unit, along with the rate of heat release and gas composition to determine the likelihood of an explosion.

Installation testing – The final phase involves testing unit-to-unit fire propagation in an enclosed space equipped with fire mitigation gear.


Currently, certification of an energy storage system to UL 9540 is not mandatory in most jurisdictions in the United States. However, the California building code has adopted the International Residential Code (IRC), which necessitates UL 9540 for ESS. Massachusetts has also recently adopted this code. It is anticipated that other cities and states across the country may follow suit, making it a requirement in the years ahead.

Even if UL 9540 is not mandatory in your area, limiting your search for energy storage systems to UL 9540-certified systems offers several advantages, including:

• Confidence in the system's rigorous safety testing

• Streamlined project permitting and approval with a single UL stamp for the entire system

• Identification of ESS manufacturers prioritizing safety and future planning by securing UL 9540 certification now

Pytes' residential energy storage batteries rely on lithium iron phosphate technology, renowned for its safety features. In contrast to most batteries utilizing cylindrical cells, Pytes' batteries employ prismatic cells, offering superior performance, longevity, and safety. For instance, the V5° batteries, a lithium iron phosphate battery, holds 5.12 kWh of energy and delivers 3.84 kW continuous charge/discharge(Max. 5.12kW-1C) capability, with a confident 10-year warranty covering 6000 cycles,. Pytes has also outfitted the battery with a proprietary high current battery management system (BMS), ensuring comprehensive protection. This BMS includes closed-loop communication and autonomously handles charge and discharge configurations, balances batteries, and enhances performance.


Pytes is now one of the few UL9540 listed lithium battery manufacturers and certainly the most cost-effective one. The Pytes V5° boasts a full range of certifications (UL 1973, UL9540 with Sol-Ark, and UL 9540(A)), facilitating quicker installation and permit approval from local authorities. Our valued customers can now install Pytes batteries worry-free.



Pytes, previously known as DLG, has been a global provider of innovative clean energy solutions for decades. Pytes' residential energy storage systems are esteemed for their safety, reliability, competitive pricing, and extensive services, covering an array of products and services such as LFP batteries, photovoltaic inverters, battery management systems, cloud monitoring, installation, maintenance, and more.



Sol-Ark is a technology firm specializing in solar and energy storage, designing and manufacturing multiple inverters and load management devices. The all-in-one hybrid inverters from Sol-Ark feature leading technology renowned for its speed, efficiency, and power, as well as exceptional versatility. In a continuous effort to expand innovative offerings, Sol-Ark has introduced string inverters and micro-inverters, broadening the range of application types.