Power Wheels Adapter for Ryobi 18V Battery Adapter Power Wheels Battery Converter Kit with Fuse & Switch and Wire Harness Connector 12AWG Wire for DIY Rc Car Toys and Ride On Truck

That is a 12v ride on car for kids, you are most likely talking about adding a ryobi 18v, you need a few things to do that. #1 a step down buck converter, this will convert it from 18v to 12v or adjustable to 12-18v, I find that 13-15v runs it much faster, any higher it has no torque for up hills and such. #2 A battery adapter for ryobi batteries, makes it easier to take them on and off, my kid could do it at 4, he is 5 now and has no problem changing the batteries out, a large ryobi last 45-60 minutes or so. Do not just hook it right to a 18v ryobi battery, you will smoke it, plus it will have no torque. I had to cut the wires of the battery converter and wire it directly to the car, I removed the factory batteries and cut those wires to use the converter and battery adapter, I screwed the buck converter to the sidewall with some small screws and shaved the outside of the screw off so my kid would not get cut by it, you can adjust the buck converters output voltage with a small screwdriver to get your desired outout, use a multimeter to adjust. step down converter https://www.amazon.com/dp/B07Y7YB14L?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_3&th=1 Battery adapter https://www.amazon.com/dp/B0CS355X37?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1