Chosen Solution
Last week I replaced a battery in the early 2013 MacBook Pro that our company has. After installation everything turned on and sounded great and the end user calibrated the new battery with no issues. Fast forward to this week: User can’t use the laptop unless it’s plugged into the charger. System information shows that the battery is fully charged although it has 0 cycles and the Amperage is 0. I’ve reset the SMC and PRAM and opened the laptop back up and the connections look good. Stumped at this point!
You probably got a bad quality battery. Try using ifixit’s battery. MacBook Pro 15" Retina (Mid 2012-Early 2013) Battery
