Are you sure? I would think it would take more than that.
Sure. I do it all the time. The Prius doesn’t use the “auxilliary battery” to run a starter. It’s just used to power up the computer. Once the computer is online, the computer-controlled inverter/regulator generates 12 volt and other power levels off the main traction battery. The electric motor/generator (smaller electric motor) is used to spin up the gas engine to idle speed if it needs to start the gas engine, and then it is fired to run it.
So all you need if your auxilliary battery is dead is enough power to get the computers to come online. The only reason you need more than a 9-volt transistor battery is that 9v is just a little too low a voltage, and the aux battery does draw down some power for recharging when you jump it.
THe 24-gauge wire gets pretty hot; I’d use 20-gauge, but 24-gauge allligator clips is what I have sitting around. I’ve heard others who use a 12-volt AA pack, but they disconnect the aux battery to start the computer.
You wouldn’t even NEED an auxilliary battery to start the car if it wasn’t for the fact that you need the computer to run the electronics to step down the traction battery voltage.
The reason I’ve jumped the car fairly often is that in the original Prius (2002 model), the aux battery was very small, and there are several things that draw power even when the car isn’t run at all. If you leave the original Prius sitting for 2 weeks, it will run down the battery (stupid design). People either start it up for a few minutes once a week, or disconnect the battery.
If you leave the indoor lights on in the car overnight, it also kills the battery.
In the hatchback version, the aux battery was bigger and you could leave the interior lights on overnight without killing the battery.