3 years ago I contacted Vinnie about this very thing and he replied:
The 30.2 LFP-V battery is custom. I try to keep a few in stock at any given time. It is $395, and installation is $75. It is a little tricky to install because it is encased in a custom metal bracket, and it is hard to take apart.
But you can also just put the battery pack inside the unit without mounting it in the bracket (just don't ship it that way - it would need to be kept stationary on your rack / shelf). Then you can easily install / remove it if you want.
Ron