Google CEO Sundar Pichai. AP Google is selling 138 US and 69 foreign patents related to battery technology, according to Fortune.

The patents, which are on sale now, are grouped into six categories, including "Hybrid," "Charging," and "Hardware." The pricing of the patents is not public and will be disclosed to potential buyers only, according to the sales document.

The document includes five "featured" patents out of the 207. These include US Patent 6,320,354 — a "Method and apparatus for battery charging" — and US Patent 5,854,549 — a "Contact arrangement having an auxiliary contact" — among others.

According to Fortune, all of the patents were originally awarded to Motorola, which Google bought for $12.5 billion (£8.7 billion) in 2011. Google later sold Motorola to Lenovo for $2.5 billion.

The purchase of Motorola was, in part, driven by the large patent portfolio the company had and Google wanted. However, a court recently said that Google held Motorola's patents in bad faith.

Google ranked fifth for the most patents awarded in 2015, behind Samsung and LG. Apple and Microsoft came in 12th and 9th, respectively.