Can I use traction battery to jump start dead 12v battery?

No.

The 12 volt battery runs the computer test that prove it would be safe to energize the HV Battery.
Without those tests the liability lawyers would have a field day suing Toyota.

 

NO. I can't even imagine what would happen if the 240VDC Hybrid battery voltage will be applied in the 13.8 VDC aux battery terminals

 

^ I'm sure there's a way to step down the voltage, but likely not practical, just robbing Peter to pay Paul?

Get a jump pack? And the latter should be purely for emergency; you do not want to be jumpstarting your car on a regular basis, that's like driving around on the temp spare, lol.

Come to think of it: that was my daughter for a few months, even drove to the States on it! That's how my jump pack sees use, too...

 

well if the user is careless to drain the 12V battery, he/she will drain the 200V battery too. and that is not good for the battery health. remember that toyota warrants that for a long time.

 

It is a safety issue for emergency first responders, who need to know that the lethal high voltage of the traction battery is isolated and contained so they won't accidentally run into it while cutting the car apart to rescue crash victims.

They already know how to kill the 12V system before cutting into anything else. This automatic high voltage shutdown means they don't have to waste more time, nor be certified in specialized hybrid procedures, to make the scene safe for themselves before starting to rescue the injured victims.

 

It is easier to have an spare small, alarm type, battery in the glove compartment with 2 small jumper cables.
By the way, it is already in the market a similar gadget made out of lithium batteries for the same purpose.
About 90 bucks

 

Bob, the typical auto supply store won't have a Prius compatible 12 volt in stock, best to research in advance. And maybe just replace it at some point, before it dies.

FYI, a JNC660 fits nicely in the underfloor tray.

 

You are right, it would be nice. But it has serious conflicts with other issues and design goals, so it didn't happen.

 

You could do it.... Sort of... And it would be pretty time consuming... It would definitely be quite unsafe. You'd have to plan ahead since you'd need access to a bunch of tools, plus wire, and some 500v safety equipment.

This would be the A-Team's solution. Only to be used in an extreme situations when the bad guys were giving you an hour before they were going to bust in and kill you.

Basically, open up the hybrid battery case to expose the individual modules. <Danger!> Using one vblock (two modules) , attach wires between end of the vblock's terminals and the corresponding 12v battery terminals, being careful not to short out the wires. Monitor 12v as it charges. Unhook once 12v is adequately charged.

Technically should work. But, you really better know what you are doing or else there will be some major trauma for you and your Prius. Seriously, don't try this unless you are comfortable and confident working with the exposed hybrid battery.

As others have noted there are much cheaper and safer solutions.

 

Amen.

 

Carry a jump start pack. $50 and no one gets electrocuted.

 

No, wouldn't do.
Prevention is the best tool..........

 

If you want to use an aircraft with redundant systems as an example, then the analogous Prius design might include a separate 12V battery reserved for emergency use only. It's not likely that Toyota would do that since Prius is trying to achieve a relatively economical price point starting in the low $20K range. I don't think you are going to find a redundant 12V battery in a luxury Mercedes costing $80K.

It's been previously suggested that you could carry a 12V jump pack to achieve the same end.

The high voltage traction battery cannot be used for this purpose because both positive and negative sides are isolated from body ground for safety reasons, and the battery is totally disconnected from the inverter when the car is IG-OFF via the system main relays. Meanwhile, the 12V battery has the negative post connected to ground. Therefore in order to tap the traction battery, you would need to bypass the system main relays and include a DC/DC converter to convert the 201.6V nominal traction battery voltage to 14V. This would be redundant with part of the inverter circuitry.

Speaking of 'juice', the car includes a fuel tank which contains a tremendous amount of chemical energy, assuming the owner is smart enough to not allow the tank to be empty. Would you say, too bad the Prius doesn't include a gas-powered electric generator to take advantage of this 'juice" and provide an emergency supplement to the 12V battery?

Any feature of that sort can be added, if you are willing to bear the cost of additional weight and materials.

 

Until Toyota documented step by step instructions EMTs were boycotting saving Prius drivers for fear of electrical issues.

http://www.evsafetytraining.org/~/media/electric%20vehicle/files/pdfs/toyota/2%20%20toyota%20prius%20hev%20erg%202nd%20gen.pdf.

Is the Gen 2 guide, there are also Gen 1 and Gen 3 guides.

"· Positive and negative high voltage power cables  connected to the HV battery pack are controlled by 12-Volt normally open relays Ž. When the vehicle is shut off, the relays stop electricity flow from the HV battery pack.
WARNING:
· Power remains in the high voltage electrical system for 5 minutes after the HV battery pack is shut off.
· Never touch, cut, or open any orange high voltage power cable or high voltage component.
· Both positive and negative power cables  are isolated from the metal chassis, so there is no possibility of shock by touching the metal chassis.
· A ground fault monitor  continuously monitors for high voltage leakage to the metal chassis while the vehicle is running. If a malfunction is detected, the vehicle computer  will illuminate the master warning light in the instrument cluster and the hybrid warning light in the LCD display.
· The HV battery pack relays will automatically open to stop electricity flow in a collision sufficient to activate the SRS airbags."

 

And you are missing the point that such a system that is sufficiently safe to not frighten away many emergency responders will be much more expensive than the 12V jump packs mentioned above.