Casio c811 battery project

[Maseman__46]

Hello, I am new here so bare with me here. I am starting a new project for my casio commando c811, becuase iam sick of the short battery life. I dont care to buy one of those big ass, expensive extended batteries. I have research this very throughly, yeilding very little results. Does anyone know the function of the 4 battery terminal pins for this phone? I am also looking for the pin resistances as well as voltages/millivoltes of the extended 4800 mah battery. I am going to combine two batteries in parrellel. I know the dangers of it, however I will not be recahrging both batteries off of my phone. I do however want the battery indicator on the phone to be functional. I will be using an external protection ic, as well as using diodes to create an isolator between the batteries to prevent any kind of back feeding between the two. I apologize if ive done anything incorrectly. Thank you in advance!!