Using Jumper cables to jump start other cars

The hmarcuse post is OK except that you must connect the negative jumper cable as well. The unpainted nut that secures the top of the Macpherson strut mount behind the main relay/fuse box is a good place for the negative cable to be clamped to.

In your case, with the Prius in front of the recipient vehicle to be jumped, you could directly access the 12V battery which is under the triangle-shaped floor piece on the right side of the hatch floor.

When jumping, the main considerations are:

1. You must get the battery polarity correct without fail. If you make a mistake, you will very likely destroy the Prius inverter which will result in a low four-figures repair bill.

2. Do not start the recipient vehicle while the jump cables are connected to a hybrid donor. Rather, make the Prius READY and let the recipient car battery charge for 20 minutes or so, drawing power over the jump cables, then disconnect the jump cables and see if the recipient vehicle will start on its own. The reason for this is that if the recipient vehicle requires substantial current from the Prius to start, you may blow one of the large fuses in the Prius 12VDC bus.

3. When connecting and disconnecting the jump cables, make sure that you do not allow electrical shorts, such as having the two cable clamps touch each other on one end while you are connecting the battery on the other end, or having a positive clamp touch body metal, etc.

4. A hybrid to hybrid jump start is easy: Not necessary to start the donor vehicle because the required current is only ~30A. Connect the jump cables, start the recipient vehicle, disconnect the jump cables. A non-hybrid to hybrid jump start is also easy and follows the same procedure.

Good luck.

 

Nope, not worth it. I have a 700 amp jump start box from Canadian Tire. If I happen to fry it, I'm out a maximum of $120, around $60 on sale.

I've used the Canadian Tire box to jump start other vehicles, including full size pickups with V8's. Works fine. You should recharge it immediately after use, and once a month otherwise

 

Patrick's explanation is excellent, though it may (perhaps should) scare you a bit.

After encountering almost the exact same situation you just faced, I thought it more prudent to look for a portable charger to carry with me just so I could provide the assistance that seems appropriate when you are driving a car with a 200 volt battery.

I started a thread in May of this past year on the topic, and it generated great information on the subject. Perhaps it will help you, as well: Jump You: Jumping a Non-Prius with a Portable Starter

 

I would not take the chance, but that's just my opinion.

 

Yikes, Patrick's explanation sure scares me. I had not thought of it before, but I like the idea of a portable charger. I am definitely going to check on getting one of those.

 

I'm not sure about the 2004-2009 prius, but I did help several people to jump start their vehicle with my 2001 prius without any problem. All of them are amazed the battery are in they trunk, and they said this design is more convenient to jump start other vehicle.

 

PATRICK is an outright GURU here. Beyond that, yep, it sure would make me wide-eyed and rather frightened to jump another vehicle. i just wouldn't do it if i did NOT have to.

that's what AAA is for right?

 

Or a portable jump start box with 700 amp capacity, that costs no more than $120 full price. So if you happen to fry it, you're out no more than $120

 

I've had to do the same thing a few time recently, as I'm trying to get one of my old cars ready to sell. I think the key as mentioned above, is use the Prius to charge the battery of the other car, not to try to start it. Other than that, just be careful and use common sense. It does sounds a bit scary, but jumping cars in general is a bit scary. You would normally be very careful not to short or reverse the cables when jumping, on the Prius you just want to be even a little more careful. I wouldn't drive around looking for people to jump start, but if the need arises its good to have the option. That said, if you're not comfortable jumping "normal" cars, the Prius is probably not a great place to start learning.

A few additional thoughts to the excellent posts above:

- Always use the jump posts under the hood, not the battery terminals in the back. I believe the terminals in the front are fuse protected. If you jump direct from the battery you lose that extra protection.

- A cheap, larger gauge (thinner wire) set of longer cables is probably safer to use on the Prius than the big beefy short ones you would normally want. Thinner gauge (and/or longer) wire will have more resistance, and drop more voltage for a given amount of current. This is a bad thing when you are trying to jump a traditional car, as you need a lot of current but need the Voltage to stay high enough to turn the starter. In the Prius, the resistance of the wire will reduce the amount of current that can flow between the cars. Whatever the voltage differential is between the Prius and the dead battery, less current will flow through a more resistive wire than a higher quality one. This will give you some measure of protection against trying to pull too much current out of the Prius when inadvertently connecting to a battery that is deeply discharged, or has a reversed or shorted cell, or someone forgets/misunderstands and tries to start the car with you still attached.

- Personally, when it comes to jumping a dead Prius I have more confidence in my own ability not to screw something up than Joe Towtruck Driver. We've already seen one likely case of a bad jumpstart by either the owner, the towtruck driver, or the dealership causing serious damage. In these situations its almost impossible to assign blame to any one party, and you'll be left holding the bag in most cases.

Rob

 

Patrick rules!

It can't be over stated: if you have *any* uncertainty about the procedure for giving or getting a jump, don't do it, and don't let some random Good Sam or tow truck driver do it. Call a Toyota dealer.

 

Of course!

Absolutely correct! DO NOT let someone jump your Prius who has not done the Prius before. Also, if a tow wants to do it for you, make certain he is willing to pay the costs of repair to your car if he fries the electronics. Under no circumstance allow someone to start a car or rev another car's engine while you have a battery-to-battery connection.