How do you refurbish a car battery. I see adds on Ebay to buy the info to do this.

You don't. All you do is possibly extend the life a bit but sulphation will reoccur. Time for a new battery.

It is very dangerous and very risky. Cheaper and easier to buy a new battery

Thanks for the advice.

I had a battery in my 1972 ford maverick and funny story at the time. I turned a really sharp corner and the battery hit the fan and cut it up bad. 5 0f the 6 cells were totally shot, I siliconed it and wrapped the battery in duct tape and it's still going strong. My grandfather had one in his truck for 16 years. It all depends on how well the battery is made and maintained