https://a.co/d/hh2N98y Something as simple as that, though I’m not sure 5v/3a is enough for a pi5 you’d have to check power specs

I would especially advise against relying on battery banks due to the heat, if you’re just going to use it in the car and already going to the trouble of customizing so much hardware I’d find a way to run a power supply off a switched 12v fuse or wire from the car - just convert to 5v/USB power. I’m sure there are generic kits online