Assuming you are in America that converter can be expensive to get through customs, not to mention shipping alone. They run on 48 volts, so you can head to any store and get 4 deep cycle batteries and matching chargers to solve that issue.
The big issue with the converter is thermal. Many do not have enough cooling and either shut down frequently in warm to hot weather or burn up. I couldnt push mines pass 17 amps or I would let the magic smoke out. In 100+ degree days I had to drive 15 minutes without it on to cool down, then when it was on it would cycle off and on as I drove.
Beats me about your car. The prius is know to illuminate the orange triangle and the Insight would generate a p1586 code. Regardless, either are easy to clear with an sg2.