Jumping/Starting Prius: What Powers What?

1. Yes. The correct name for that mode is ACC-ON. The Prius has four possible modes: IG-OFF, ACC-ON, IG-ON, and READY. ACC-ON will drain the 12V battery somewhat. IG-ON, where all the dashboard warning lights are on, will drain the 12V battery very quickly. So minimize the time when the car is left IG-ON for sure. If your 12V battery is in decent condition, you can use ACC-ON for a reasonable period of time.

2. No

3. Your assumption is somewhat correct. The 12V battery provides power to boot up the ECUs. The high voltage traction battery provides power to spin MG1 which acts as a starter for the gasoline engine.

4. The 12V battery can be 75% discharged or more and still boot the ECUs which is prerequisite to starting the car. However, since you don't have a good way to know how deeply discharged the 12V battery is - unless you carry around a digital multimeter - this probably is a useless metric for you.

5. The jump cables can either be attached directly to the 12V battery or to the dedicated positive jumpstart terminal in the main relay/fuse box next to the inverter, and an unpainted metal piece attached to the body, for example a front strut nut on the coil tower behind the relay/fuse box. Make sure the correct cable polarity is observed: positive to positive, negative to negative or body ground. If you make a mistake there, you may destroy the inverter.

6. I do not understand your question.

 

Probably less than nearly any other vehicle.
The 12 volt is vital to starting the Prius because it powers the boot up of the system that allows it to start. But it's the hybrid battery and as Patrick explains above, the MG1 that "actually" starts the engine.

Since I'm very nearly simple minded, I think of it this way. If starting the Prius is a "Horse Race"? Then the 12 volt battery is the "Starting Gun"...but the Hybrid Battery is the "Gate"...

In other words, you need the 12 volt battery to get things started...but it's not really directly starting anything but a computer boot up.

I own one of those power station back-up jumper, compressors. Nice tool. But I own it primarily to keep my tires inflated, and for the situation that might arise if anyone needed a jump and I did NOT want to use my Prius.

Given the complexity and possible fragility of the electronics in a Prius, my philosophy is to avoid jump starts absolutely as much as possible.

But my guess is that The Prius doesn't need any MORE power from one of those systems than any other regular 12 volt battery might need, and since it's doing a boot up...not a cold engine crank..perhaps less. Therefore it's my speculative guess that any relatively new, personal battery jumper systems that was charged and ready, would probably have enough power.

But my recommendation is to simply keep an eye on your 12 volt, replace before ultimate failure...and avoid having to be jumped started.
Yes, The Prius can be jump started, but I want to avoid the risk if possible....also as pointed out follow directions carefully IF you have to jump start The Prius.

And I tell my friends, I have a personal jump start machine, they can borrow or try...but The Prius isn't going to be GIVING anyone a jump start. Sorry, but I'm not risking damage to my 20,000 dollar Prius...so you can start you 1200 dollar 1998 Ford Mustang.

The Prius forces me to be a bit unfriendly in this manner.

 

For playing the radio, etc, when stopped, I usually just leave the car in "ready" mode (and lock the doors, if in a populated area). That way, there's no draw-down on the 12v battery. If the climate control is off, the engine usually stays off too.

I think I read of someone booting up a Prius with a stack of D-cell alkalines (I guess it would take 8 of them).

The state of the 12v battery is commonly overlooked on Prii since there are no slow-cranking symptoms like other cars when the 12v becomes weak. It usually just will either boot up...or it won't.

 

+1 from taglefoot.

Maybe best for you to just leave the car on READY mode, if sitting and listening to radio, assuming you are in a well ventilated area. Yes, the engine will cycle on/off intermittently to maintain the HV battery charge, since the 12V is drawing from the HV battery. But you won't have to wonder if listening to the radio will kill the 12V battery. Yes, your overall gas mileage will take an insignificant hit, "idling" to keep the HV battery charged.

Get a 12V booster jump pack of your choice; pricy though.
Amazon.com: 12v booster battery - Jump Starters / Jump Starters, Battery Chargers & Portable...: Automotive

Or a cheaper alternative is just to get a sealed lead acid battery, as your back-up 12V booster. A 7, 8, 9, or 12Amp Hour SLA (Sealed Lead Acid) battery, should be more than sufficient to boot up the Prius ECU. I opened my dead portable jump pack and saw a small 7Amp Hour SLA inside it; thus the 7Amp Hour SLA being the smallest one to get.
Amazon.com: 12v sealed lead acid battery: Automotive
The 12V booster jump packs all contain a sealed lead acid battery (small to large Amp Hour battery), but come in a nice carrying case with battery clamp cables attached. You could always fabricate a simple battery camp attachment of your choice as well.

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