DETROIT — Wanxiang Group, a large Chinese auto parts maker, won a high-stakes auction on Sunday for assets of A123 Systems, the bankrupt American battery maker that was a centerpiece of the Obama administration’s loan program for electric vehicles.

A123, which filed for bankruptcy in October after chronic losses and a damaging battery recall, said Wanxiang agreed to pay $256 million for its automotive and commercial operations, including its three factories in the United States.

But the sale excludes A123’s business with the United States government and its military contracts. That portion of the company will be sold to a small energy company based in Illinois, Navitas Systems, for $2.2 million.

Spinning off the government-related business to an American buyer was meant to quell concerns about transferring sensitive military technology to the Chinese, said A123’s chief executive, David Vieau.