Chrysler Group saw big sales gains in the first quarter but its results were overshadowed by charges related to its merger with Italian automaker Fiat. Chrysler lost $690 million in the January-march quarter. Without one-time charges related to the merger, the company’s net profit more than doubled to $486 million. Revenue rose 23 percent to $19 billion. Chrysler’s global vehicle sales rose 10 percent to 621,000, while in the United States, the company’s biggest market, Chrysler sales jumped 11 percent, far outpacing the 1 percent average gain for the industry. In January, Fiat paid $3.65 billion to a union-run healthcare trust to acquire Chrysler’s remaining shares. Under the deal, Chrysler agreed to pay $700 million to upgrade its factories, and the company took a $672 million first-quarter charge to meet the commitments.