I offer 1year warranty, technical support if something goes wrong or question arises.
If problems arise later down the line, you can always go to an official Nissan dealership with it. It's still their battery! Or you can g back to the battery installer.
This will be done on cars that already have the OEM 5/8year warranty expired. I don't think people need another 8 year warranty on packs that are 1/2 the price of Nissan.