The record home run came one day after the red-hot Carpenter hit three home runs with seven RBIs as part of his 5-for-5 day at the plate in an 18-5 win over the Cubs.
St. Louis pulled within one on Molina's sacrifice fly in the seventh, but Chicago responded with four runs in the bottom half.
He now has 25 home runs this season, including 10 this month, making him the first Cardinals player with 10 homers in July since Jim Edmonds hit 13 in July 2004, according to ESPN Stats & Info.
Carpenter hit a two-run homer in the second inning off Lester. Carpenter doubled twice in the fourth and hit a three-run drive off reliever Brian Duensing in the sixth. Weaver allowed seven hits and walked five in his team-high 20th start of the season.
Matt Carpenter is having a better day than you. "He's got his own personal plan, and he's committed to it and he's putting good swings on the ball". "When it leaves my hand, it's out of my control and it is what it is".
The Cubs added reliever Jesse Chavez to their roster and placed right-hander Anthony Bass on the 10-day disabled list with a back injury. The move is retroactive to Friday, a day after Martinez struggled through five innings in a 9-6 loss to the Cubs. RHP Miles Mikolas was activated from the paternity list and reliever John Brebbia was recalled from Triple-A Memphis.
Cardinals first baseman Matt Carpenter was locked in Friday.
Cubs: LHP Jose Quintana starts Sunday for the first time since July 10.