Data analysis by ADAC on battery lifespan in plug-in hybrids

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Whether electric car or plug-in hybrid, the durability of a traction battery is a question that concerns those who exceed the warranty period with their ownership duration or want to purchase an older used car, especially given its high proportion of the price. In general, a professional battery check is also important before buying a used plug-in hybrid, as ADAC now advises once again based on a large data analysis.

As durable as combustion engines

The more and the longer such batteries are in circulation, the more clearly it is gratifyingly shown that the remaining capacities estimated by the manufacturers are almost always significantly exceeded. Although not directly comparable, it shows that the batteries are at least as durable as combustion engines. A large study by P3 Group and Aviloo on battery health (State of Health, SoH) underpinned this finding at the end of last year with a test pool of over 7000 electric cars. SoH quantifies what percentage of a battery's original capacity is available at the time of measurement.

Today, ADAC is publishing the results of its study of batteries in plug-in hybrid cars. Aviloo was again involved in this study; as a provider of independent battery tests, it is a market leader with a large treasure trove of data from thousands of investigations. In cooperation with the automobile club, the battery specialist has evaluated around 28,500 SoH measurement results from cars from six different manufacturers. The results are not surprising. However, the gratifying finding that the traction battery in plug-in hybrids will generally remain usable for at least as long as the rest of the vehicle should be stated first. It is not surprising that battery aging proceeds very differently depending on the proportion of electric driving. A higher proportion of electrically covered distances ages the battery faster due to more frequent charging cycles.

The brand makes the difference

However, manufacturer-specific aging speeds are also emerging. For example, batteries in Mercedes-Benz cars age the slowest. Cars from the Volkswagen brands have very consistently degrading batteries, with only a few outliers downward. In contrast, cars from BMW, including the Mini brand, are more affected by this. Ford shows stronger aging at the beginning, which then decreases over the lifetime, but with too few batteries measured so far. ADAC describes the data from Mitsubishi as “tendentially conspicuous”: here, battery aging typically occurs early and pronounced before subsiding later.

More important is how the energy storage is handled: if the charge level is kept between 20 and 80 percent during the usage period and the full capacity is only charged shortly before a long journey, significantly less wear can be observed. A larger battery is also helpful to keep the number of charging cycles low. Given the wide spread of results, a battery check before buying a used plug-in hybrid is all the more important. ADAC considers the following SoH values to be the minimum:

• 92 percent at 50,000
• 88 percent at 100,000
• 84 percent at 150,000
• 80 percent at 200,000 km mileage

Alternative: Electric car

In light of the data collected, the automobile club also reiterates that an exclusively battery-electric car is often the better alternative to a plug-in hybrid if as many driving routes as possible are to be covered electrically. ADAC advises those who are hesitant that modern electric cars are already fully suitable for everyday use based on their own test experience. Their advantage is that their larger batteries last the longest anyway, simply because of the lower number of charging cycles.

(fpi)