Replacing batteries in Electric Mobility Rascal 3-wheel scooter

I put new batteries in the scooter but the negative wire doesn't reach the battery terminal. It has been 4+ years since I have worked on it and had the batteries out to prevent corrosion. I attached jumper wires to each battery but only the horn works. Do I also need to charge new batteries before use? I looked for a serial or model number but only found a small sticker under the frame.
DH