Pismo pram pin-out

Does anyone know the pin-out for the pram battery on a Powerbook Pismo?
I know its 6 volts and it has three wires; red, black and white. I would assume red is + and but what are white and black? One is - but the other?

A couple 3V button cells are cheap, but the pram for the Pismo is twenty+ bucks.

( Ok, I am cheap)

Thanks for any help!

Any one?...

I have one in bits somewhere. I suspect the white is also positive, just a different voltage from the red one.

Different voltage, hummm..maybe three volts?

(Mine reads "0" on all three wires)