Reviving old batteries?

I purchase auction cars and dead car that batteries are dead some for months and other for years. ..
I have pretty good luck reviving them,especially the ones that look new but have no voltage.
Get a fully charged battery and hook up jumper cables to the dead battery and let it sit for a day,you want to get some voltage in the dead battery.
You can also hook up a jumper box to it for a day.
After that put it on 2 amp charge for 24 hours on some I have charged them with the jumper cables and good battery hooked up for the first couple of hours.Your jumper box or good battery will have to charged also.
Sone batteries that are revived do have less cranking amps than when new but work.