[BC] I installed a Black Panther in my NSX recently. Removal of the old battery was simple:

 
 Remove spare tire and tire holder 

 
Disconnect old battery (negative first, then positive) 

 
Loosen nuts on battery hold down and remove it 

 
Slide old battery forward and lift out - it is in an outer casing that has convenient      hand grips, but if you have a bad back you are in trouble. 

Installation required a bit of fooling around due to the new battery’s smaller than stock size:

 
 Turn the battery casing 180 degrees so the higher (splash guard?) edge is facing      backwards (but you will still install the battery with the positive terminal on the      driver's side) 

 
Put something on the bottom of the casing to raise the floor up an inch or two. I used a      heavy plastic VHS tape box. 

 
Put the new battery in the casing pushed all the way to the right side. 

I found the above steps necessary because the Panther is shorter and needs to be raised and placed differently in the casing so the battery hold down bar can work and so the positive cable can reach the terminal (there is very little slack on this cable).

 
 Lower the casing with the new battery into the car and slide back into place. 

 
Attach the positive cable first (red). 

STOP!    WARNING!     DANGER!

 
 If you have an aftermarket alarm with power interrupt detection and a siren mounted in      the front compartment you are likely to have a million decibels blasted into your ears      when you attach the negative cable. Plug your ears and muffle the siren with some towels      if you don't want to be saying "What? Did you say Shave Ezra?". 

 
Attach the negative cable... the hold down bar... spare tire... cross your fingers and      crank her up. The battery comes already charged to capacity.

Do It Yourself