Sonnen achieves a record lifespan with its batteries

Sonnen achieves a record lifespan with its batteries

  • July 22, 2021

Through long term testing sonnen has now achieved a significantly longer lifespan for their batteries, than previously assumed

How long do batteries actually last? This question is crucial for the use of batteries in electricity storage systems. The longer the service life, the more economical and sustainable its use.

Since there is little long-term data on the service life of batteries in power storage systems, sonnen has been running its own battery laboratory at its headquarters in Wildpoldsried for many years. There, batteries from different manufacturers are checked over long periods of time and their service life is measured.

In one of these long-term tests, which has now been running for almost eight years, a lithium iron phosphate battery type (LFP) used in the sonnenBatterie has already achieved over 28,000 charging cycles. This means that the battery cell has been fully charged and discharged 28,000 times. It still has 65 percent of its original capacity and has not yet reached the end of its service life. ¹

In sonnen’s battery laboratory, the LFP battery cell was exposed to much harsher conditions than would be the norm for a power storage unit in a household. It was fully charged and discharged several times a day, which put a greater strain on the battery. The tests were carried out with a C-rate of 1 and 100 percent depth of discharge. This means that the battery cell was fully charged within an hour and fully discharged again within an hour.

In everyday life, however, less than one full charge and discharge per day is common – in Germany a home storage device completes around 250 charging cycles per year – less than 1% of the cycles now measured in the laboratory.

“The test results achieved so far go beyond the service life forecasts of the battery technology we use. This is an important quality confirmation for our customers. And if you have a long-life battery, you will also benefit economically for a longer period of time “, says sonnen CEO Oliver Koch and adds:” With this we can also prove that this is also the right  technology for our virtual power plant, which also uses the batteries for self-consumption ” .

In addition to testing individual battery cells, sonnen is also testing battery modules. A battery module that consists of over 200 battery cells of the same type has already achieved over 10,000 charging cycles. After 10,000 charging cycles, the module still had 83% of its output capacity and is thus even above the guaranteed value of 80%.

The longer a battery lasts, the more efficiently the resources used for production are used. A battery that can be charged and discharged 10,000 or 20,000 times can provide significantly more energy than less durable batteries with the same use of resources.

¹ The end of the service life of lithium-ion batteries occurs when the available capacity suddenly decreases.

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