BYD powers ahead in independent battery testing
An independent testing program and market analysis from Germany has demonstrated how leading residential battery and inverter manufacturers are achieving impressive system efficiency and performance. Improvements delivering results include both reducing power consumption in standby mode and increasing efficiency under low load.
Leading battery and inverter makers are delivering systems that can achieve over 92% in the 5kW power class, and close to or above 95% at 10kW. The results achieved by Chinese EV and battery maker BYD were a particular highlight, with five different BYD systems in two power categories achieving top-five positions.
The fruits of BYD’s partnership with Austrian inverter supplier Fronius was also on display, with systems coupling the two manufacturers’ products achieving podium finishes. A BYD and Fronius system took out equal first place in the 5kW class category and equal second in the 10kW category.
The testing outcome confirms that the Chinese giant is delivering high quality batteries as its EV business rapidly expands as well. On March 25, BYD announced that it had produced seven million EVs – with its manufacturing of what it dubs “new energy vehicles” ramping at an impressive pace.
In what looks like exponential growth, BYD reports that it produced 1 million EVs by May 2021, 3 million by December 2022, and 5 million at September 2023.
Testing program
The residential battery testing program was conducted by the research institute the HTW (Berliner Hochschule für Technik und Wirtschaft) in Berlin. The testing and analysis program, in its seventh year, is called the Energy Storage Inspection, or “Stromspeicher-Inspektion”.
12 manufacturers took part in the 2024 HTW testing program, for a total of 18 systems. In addition, two systems were purchased from the market and tested.
“The [BYD] Battery Box is a good performer,” said Lucas Meissner, a research analyst at the HTW. “We tested different battery boxes this year and BYD makes a good battery, year after year.”
For its testing program, the HTW has developed the System Performance Index (SPI) by which it can assess the battery and inverter systems. Meissner reports that, with installation rates in Germany surging, there is growing interest in the results.
“There can be a huge gap between the data sheet and the things we see and publish for all to see.” Not all battery suppliers agree to have their results published.
Results in detail
BYD, as proven in the results, has nothing to hide. In the 5kW category, the BYD Battery-Box HVS 7.7 in combination with a Fronius Primo GEN24 6.0 Plus inverter could achieve 92.6 % efficiency, as its SPI score. When coupled to the Kostal Plenticore plus G2 5.5 inverter, the same BYD battery hit 92.3%.
The results saw BYD dominate the podium. In the 5kW efficiency table, the BYD Battery-Box HVS 7.7 coupled with a Fronius inverter shared the number one spot. The other equal-first spot was from was a battery and inverter combination from RCT Power – with its Power Storage DC 6.0 and Power Battery 7.6 also hitting 92.6%.
For larger batteries, in the 10kW category BYD had four batteries in the top 10. BYD Battery-Box HVS systems shared the second place, and then positions five, eight and 10 when coupled with different inverters.
The BYD and Fronius partnership was again a standout. The BYD Battery-Box HVS 10.2 in combination with the Fronius Primo GEN24 10.0 Plus achieved 95.4%, for its equal second-place finish. The leading battery in 10kW was again from RCT Power – the company’s Power Storage DC 10 and Power Battery 11.5 topping the rankings with 96.4%.
“We value the SPI tests by HTW as they provide an independent third-party guidance for system choices,” said Feng Jiang, Head of Residential, Storage System at BYD in a statement. “This once again demonstrated the versatility of the Battery-Box system, which can be used in a wide variety of applications scenarios.”
BYD has participated in the HTW battery testing program since its inception.
Findings from the testing program are providing battery and power electronics makers with actionable findings, leading to efficiency gains. “There are a lot of manufacturers that have been taking in our advice and putting that into the development of their systems,” said HTW’s Meissner.
Efficiency impacts
The HTW researchers have crunched the numbers to demonstrate how battery system performance impacts system paybacks for German households, making clear the value of high operational efficiency.
For a 10kW battery system, the HTW team found that losses due to less efficient operation can cost households between €94 and €276 a year ($155 and $457). Over 10 years, the economic losses blow out to a whopping €1820 ($3010).
Standby consumption, low load
Two areas in which reduced efficiency can impact overall performance – the STI as calculated by the HTW – significantly. Battery systems can consume power when on standby mode, resulting in less power available for use within the households. However, the HTW team observes that manufacturers have made strides in reducing standby power consumption.
By contrast, a wide range of system efficiencies when under only partial load was observed. The HTW paid particular attention to this aspect of system performance in its 2024 program as it is commonplace for batteries to discharge when there is a low level of power consumption occurring within the household.
While charged during daylight hours, residential batteries are called on during the evening hours – when the household returns from work or school. However, even when everyone is in bed, there remain light electrical loads like refrigerators, or heavier loads such as air conditioning. If the battery system operates at low efficiency under this load, there are significant impacts on the system efficiency.
“If a battery inverter is not efficient during that time, and it can be around 60% efficiency, then there are significant losses,” said Meissner. As a result, “the battery discharges really fast when compared to highly efficient inverters.”
The HTW invites all residential battery makers to participate in the annual Energy Storage Inspection program.