The NL West-leading Giants have won four straight and eight of nine. The Braves, who lead the NL East, have lost five straight, their longest skid in two years.
The Giants have hit homers in 10 straight games, matching their longest run in almost four years. They trail only Colorado among the NL home-run leaders.
"I don't think we'll hit this many home runs, but I said before the season started this team is going to have more power," Bochy said.
The Giants got only four hits. They scored all their runs on homers for the second straight night after hitting two homers in Friday night's 2-1 win.
Posey, from Leesburg, Georgia, hit his first homer at Turner Field.
"That is cool," Posey said. "I watched so many games here -- not so much coming here, but on TV."
Ryan Vogelsong (1-1) allowed one run on five hits and four walks in six innings. The Giants have won the first two games of the weekend series with their last two starters in the rotation. Tim Lincecum took the win on Friday night.
"It's great for that to happen," Bochy said. "... When you score two runs in the first one and three in the second and win both games, it's not easy to do and it's a credit to the pitching."
Julio Teheran (2-2) gave up just four hits with no walks in seven innings, but allowed a season-high three runs. The three homers allowed set a career high.
Teheran said the homers were his only three mistakes.
"They were the pitches that I wanted to throw and where I wanted to throw them but I have to take my hat off to them," Teheran said. "... All my pitches were working really good. I made three mistakes and it cost me three runs."
Belt did not start in Friday night's game and was in a 1-for-21 slump with 12 strikeouts before he led off the second inning with his eighth homer.
"That was a great swing," Bochy said. "I think he's real close to being where he needs to be."
The Braves' only run came in the third. Jason Heyward walked, stole second and scored on B.J. Upton's double to the left-field wall.
Posey homered in the fourth for a 2-1 lead. His seventh homer landed in the first row behind the left-field wall.
Morse led off the seventh with a towering drive into the seats in left-center. He has five homers in his past 10 games, including back-to-back games against the Braves.
The Braves' hitting woes continued as they stranded seven baserunners. They were held to one run by Giants pitching for the second straight game and have scored no more than one run in 11 of 29 games this season.
"Same story as last night," said Chris Johnson, who was 0-for-4. "We left a lot of guys on base, myself included. You can't win a ball game when you leave that many guys on base."
Each team wore Negro Leagues throwback uniforms for the Heritage Game -- the Atlanta Black Crackers and the 1946 San Francisco Sea Lions. Each ensemble featured high socks.
The last time the Giants hit homers in 10 straight games was from Sept. 23-Oct. 3, 2010. ... Of Belt's eight homers, seven have come on the road. ... Atlanta's last five-game losing streak was May 21-28, 2012. ... Lincecum wore fake glasses and had a towel tucked under his shirt when he delivered the lineup card. "I hope he wasn't impersonating me," Bochy said before taking a glance at his stomach. "I don't think it's that big." ... Braves manager Fredi Gonzalez said he expects to announce a roster move on Sunday to clear a spot for RHP Gavin Floyd, who has completed his rehab from 2013 elbow surgery while with the White Sox. Floyd's role has not been revealed. ... The series concludes Sunday when Atlanta's Alex Wood faces San Francisco's Madison Bumgarner in a matchup of left-handers.