Carbon Pile 12 Volt Battery Load Tester For Testing Batteries At Home
The batteries will need to be removed from the scooter before load testing. I recommend drawing a picture or taking a photograph of the wiring harness before removing it from the batteries so you will know how to reinstall it back onto the batteries when they are reinstalled into the scooter.
If the batteries test bad then replacing them would be the next step. If they test good then I would look into replacing the speed controller as the next step.
Please let me know if you have any questions.