Google has big ambitions when it comes to self-driving cars and energy, but that isn’t stopping the company from selling a batch of patents related to battery technology.

The tech giant is auctioning 138 U.S. patents and 69 foreign ones, according to a sales document. The company has clustered the patents into six categories that include “Hybrid Batteries,” “Charging” and “Hardware,” and is currently accepting bids.

The document (posted below) also points to five “featured patents,” which are presumably among the most desirable, that include U.S. Patent 6320354, titled “Method and apparatus for battery charging.”

Google did not reply to a request for comment about the reason for the sale, but the answer may be gleaned from patent records. Those records show the U.S. Patent Office originally awarded all of the patents in question to Motorola, the phone maker that Google acquired in 2011 for $12.5 billion dollars, and then sold to Lenovo in 2014.

At the time, Google GOOG was embroiled in a bitter legal battle with Microsoft and other rivals in the mobile phone industry. Its decision to purchase Motorola was widely regarded as a means to get the company’s approximately 17,000 patents, and counter-attack against a slew of lawsuits.

The Motorola gambit, however, occasionally backfired. Last year, for instance, an appeals court found that Google had used some of the patents in bad faith, and upheld a jury award for it to pay its rival $14 million.

As such, Google’s auctioning of the patents likely amounts to a decision to dump an unneeded asset rather than a larger strategic pivot. The move comes even as Google researches batteries and contemplates partnering with auto makers on self-driving cars.

To learn more about battery tech, check out this Fortune video:

Meanwhile, Google has also been pursuing a low-key strategy to neutralize the intellectual property battles, which have been ruinously expensive for the tech industry. This strategy has involved distributing patents to startups on the condition they join a mutual non-aggression pact with other tech companies.

Google in recent years has become a patent powerhouse. On Wednesday, it landed at No. 5 on an annual list of companies that received the most patents.

In the case of the Motorola patents, it’s unclear if Google is taking measures to ensure they will not fall into the hands of so-called “patent trolls,” which are shell companies that make a business of amassing old patents in order to demand payments from productive businesses.

Here’s a copy of the auction document, which was spotted by IAM Market:

Google – Battery – Portfolio