Throttle/Pedal Issues 2012 PH Series Precedent

[GeauxTigahs]

Hello everyone. I'm new to the world of golf cart ownership. I purchased a 2012 PH series 48v golf cart used from an individual. The speed controller was changed with a refurbished Golfarama 1515 around a week ago. One of my issues is that the cart will only start with the pedal pressed 10-15%. If you go past that the cart will not start. Also once it is going if you go past 50% throttle then cart will completely die. Any ideas on what this could be? I also did a load test with the batteries after a full charge and each one dropped around 1.5v. They are the PD plus batteries and just by judging the letter and date they appear to be 4 years old. Any help would be greatly appreciated!