I've been building these power supplies for over 2 years now, for some of my racing buddies as well as for sale @$10 each.
Depending on the PC powersupply in question, they put out between 5.0 to 8.0A at 11.5V. They are extremely stable for me, and works 24hrs a day without complain. They only thing is not to overload them. I tried 9A on my charger and it began to smell lol.
I'm desperately interested in knowing how to jack up the voltage to 13.8V since my latest charger does not have step up ability and struggles to charge 8 cells.