I've used Optima batteries for years in my 69 Camaro and 77 GMC truck, and now that the OEM Honda unit died, it's time to drop one in the NSX. I did a little research and found the size I need was the 34R. The "R" means "reverse pole position" so the positive terminal is on the right side, which works out better for the NSX. Batteries Plus had one in stock for $119. Remember kids - this battery has a full 3 year replacement warranty, and 72 months prorated. They believe in their products!
The Honda battery is taller and heavier then the 34R.
Pulling the old battery out kind of sucks because I have that nifty oil cooler up front, so it had to come out first. A little mess and 2 minutes later it was out. Since the Optima 34R is shorter than the factory piece, I needed a 1-1/4" spacer for the bottom of the box. Optima makes a 1-1/8" spacer that snaps on to the bottom of their battery, so I had to slice off 1/8" off the front lip of the battery box to get the hold down to do its job correctly. A straight edge, Exacto knife a 5 minutes made a factory looking reduction in the height of the front lip.
Next I cleaned, wire brushed and sprayed with contact cleaner the two cable ends. They were in pretty good shape so it was quick work. I also took the opportunity to clean everything in and around the box and lower tray area as well, so it's all shiny.
Spacer installed on bottom of battery.
Installing the box and battery took very little time, but getting the positive cable on the post was a bit of a stretch. You can see that the posts are well away from contacting anything and pretty easy to get to - that is until I put the oil cooler back in.
The Optima 34R installed in the Red Car.