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An Expert Review of LG Chem RESU ESS

Solarkobo Score: 4.6/5

Introducing Energy Storage Systems (ESS)

Batteries have been in use for a rather long time both in standalone off-grid setups and in backup power systems. In recent years, however, there has been a significant surge in the popularity of domestic energy storage systems. One of the main drivers behind this trend is the desire for energy security.

Lithium-ion batteries, now recently being offered as 'energy storage systems' or ESS, that is, with advanced features and supporting components that may or may not include a hybrid inverter, MPPT capabilities and a battery management unit, and in 'modular' designs that make them easy to install and used as plug-and-play devices, have grown in popularity over the years. One of the many reasons for this includes the increase in research efforts. For instance, the 2019 Nobel Prize in Physics was awarded for research in Lithium-ion battery technology. Also, the success of the Powerwall and the electric vehicle industry has had a profound effect on the ESS market especially. While lithium-based battery cell technologies are still the costliest of the existing battery technologies, production costs are being driven down by optimal manufacturing processes to meet the boom in demand and more competition that has driven major players in the solar industry into the energy storage segment of the market.

Manufacturer's Profile

The makers of LG Chem ESS is LG Chem Ltd., also often referred to as LG Chemical, a Korean company owned by LG Corporation. LG Chem manufactured Korea's first lithium-ion batteries in 1999 and by the end of 2011, it had become the world's third-largest manufacturer.

In September 2020, LG Energy Solutions, the company under which LG makes its ESS, was spun off from LG Chem. It now accounts for more than 20% of the global electric vehicle battery market and supplies giants including Tesla, General Motors and Volkswagen. It also supplies batteries for drones and ships and battery-powered spacesuits to NASA.

LG is one of the most notable brands in the electronics industry. In keeping with the renown of the LG brand its ESS, the LG Residential Energy Storage Unit or LG RESU for short, is one of the more well known and most respected ESS brands in the energy storage industry. It competes well with other ESS giants, including Tesla, BYD, Panasonic and Samsung.

LG Chem RESU complete range

The LG Chem RESU

LG offers its ESS as the LG RESU or 'Residential Energy Storage Unit.'

General Features of the LG Chem RESU

Cell Chemistry

The LG RESU batteries are made from Lithium (nickel manganese cobalt oxide) NMC pouch cells. The NMC pouch cells is the choice cell technology used in many electric car manufacturers. They are safe and long-lasting. The unique Polymer 'pouch' flat laminated battery design (PH3) enables their batteries to have much higher energy density with increased reliability and safety. Designing the cell structure in this way reduces the likelihood of failure and enables an even distribution of heat across the cell area.

Battery Management System

They incorporate a Battery Management System (BMS) that allows users to monitor the battery state information such as voltage, current and temperature and troubleshoot abnormal symptoms that lead to energy losses over time. They also have inbuilt sensors that monitors cell temperature and voltage and helps extend battery life. Also, the LG BMS system lowers the power output by 50% once the internal cell temperature rises above 50°C and further lowers power output completely once the temperature goes above 55°C. In this way, it helps reduce degradation and the chance of thermal runaway.

95% Depth of discharge (DoD).

The DoD of a battery is the level that the battery can be discharged without damaging it. The RESU batteries allow up to 90% DoD with the exception of the 16kWh variant which allows up to 100% DoD.

Compatibility With Industry-Standard Inverters

Unlike the Tesla which is limited to two inverter types, the RESU battery models are compatible with a wide range of industry-standard solar and hybrid inverters, including Huawei, Growatt and Victron, allowing buyers a wide range of options that they can integrate with their batteries.


LG RESU batteries are maintenance-free meaning that they do not require any maintenance checks during their entire lifespan. Their design eliminate worries about constant maintenance and the attending costs and potential hazards.

Roundtrip Efficiency

A battery's roundtrip efficiency is the measure of electrical losses involved with cycling the battery. The higher the roundtrip efficiency percentage, the more efficiently the battery can store and afterwards release the electricity it receives. The LG Chem RESU batteries have a roundtrip efficiency of 94.5%, one of the best in the market.

IP55 Rated

All LG RESU batteries have an Ingress Protection rating of 55. This means they can be installed in a semi-outdoor location such as a verandah or carport, though they are not to be exposed to direct sunlight.

Natural Cooling

They are designed to be cooled through the flow of natural air flow onto the slit-shaped frame of the batteries.


LG Energy Solutions guarantees that their batteries will retain at least 60% of storage capacity for either 10 years after the date of the initial installation or for a Minimum Energy Throughput, (22.4MWh), whichever comes first. LG Chem will either fix, replace, or refund the cost of the battery if its capacity degrades faster than specified in the warranty terms. This matches the industry standard warranty offering by the leading brands.

Product Line

The RESU comes in two product lines, 48V and 400V.

The 48V Line

The 48V line includes the RESU3.3 (3.3kWh), RESU6.5 (6.5kWh), RESU10 (0kWh) and RESU13 (13kWh). The 48V line batteries are designed to be used in both hybrid and off-grid setups.

The 400V Line

The 400V line includes the RESU7H (7kWh) and RESU10H (20H). They come in Type-R (Communication via RS485) and Type-C (Communicates via CAN2.0B) options. The 400V batteries are designed for use in hybrid set-ups and cannot be used in off-grid applications.

The RESU Prime and RESU Flex

The Prime and Flex were released in March 2021. They are more advanced than the 48V and 400V batteries and are capable of handling up to 100% DoD. They are guaranteed to retain 70% of their capacity after 10 years. They are built with newly-developed battery cells with a higher power density than the previous RESU batteries allowing higher overall storage capacities. They are also modular, meaning that multiple batteries can be stacked together to reach larger output power ratings. They come in different variants for floor and wall mounting.

The LG RESU Prime are available in two sizes, the Resu 10H Prime with a capacity of 9.6 kWh and the Resu 16H Prime with a capacity of 16 kWh. They incorporate a converter that enables them to operate with high-voltage battery inverters.

The LG RESU10H Prime
The LG RESU10H Prime

The LG RESU Flex series batteries were designed for use with hybrid inverters. It does not require the converter used by the Prime series. They incorporate a Battery Protection Unit (BPU) and a minimum of two battery modules called the Battery Module Assembly (BMA) with each battery module has a capacity of 4.3 kWh and can be customized to meet the user's requirements by expanding from 2 to 4 battery modules at different stages. The RESU FLEX system can be scaled up to 17.2 kWh.

The LG Chem RESU FLEX for Floor Mouting
The RESU FLEX for Floor Mounting

Additionally, two systems can be combined and operated in series to achieve a total capacity of 34.4 kWh. In the complete RESU FLEX system, four battery modules are connected in series to achieve a voltage range of 384 - 531.2 V.

They come in three models, FLEX 8.6, FLEX 12.9 and FLEX 17.2 with 2, 3 and 4 modules respectively and can be single- or 3-phased.

The RESU FLEX 12.9 for Wall Mounting, in 3 Modules.
The RESU FLEX 12.9 for Wall Mounting, in 3 Modules.
Our Thoughts

LG Chem’s RESU batteries are part of the new generation of powerful ESS. It is one of the leading Tesla Powerwall alternatives and is nearly as popular as the Tesla. However, though individual modules can be installed in combination with each other, they lack the flexible modular structure that makes for easy scaling, a quality that ESS are now generally known for. Regardless, the newer RESU Flex was designed with modular flexibility as key consideration and taking feedback from installers. LG maintains a relationship with other industry players, mostly installers and are open to receiving useful feedback.

Also, the Powerwall beats them with a wider range of operating temperature This means that they may struggle to perform optimally in temperatures above 50C over long periods of time. On price points, the LG RESU batteries are priced competitively per kWh below the Tesla Powerwall but at par with major ESS brands like AlphaESS, PylonTech, BYD and Huawei.

In general, LG RESU batteries share in the premium reputation of one of the world's most trusted brands. They compete favourably with the Powerwall, which is the benchmark for ESS systems for quality. In terms of quality, longevity and performance, there are very few brands in the ESS market that can match them. SolarKobo is always happen to recommend them to our clients, especially where price is not a major consideration.

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