Thinkpad Laptop Battery pinout (External charging)

[Mmouse]

Hey guys thanks in advance for the help. I want to be able to charge my laptop batteries just from a variable DC charger but I dont have any schematics. Is there a general pinout for these battery charging contacts or is it different for each. If so I am primarily interested in older Thinkpads (A31 ... etc) as I have come into a bunch with faulty charger or motherboard charging issues. Thanks again. steve