It's Toyota cheaping out as always. They put a 1.5kWh NiMH pack in the trunk, and charge $5k for replacement. That's almost a big power bank capacity, and using that small of a battery strains it too. Cost for enclosures and control circuits don't scale with capacity so dollar/kWh figure is atrocious.

It works. People hates it. The issues with it are mostly theoretical or matters of preferences. That's hallmark Toyota, isn't it...