Jumping a dead battery

Just follow the instructions provided in your owners handbook to jump the battery. The battery is small as it only has to boot up the computers that operate your Prius. There are several threads that show how to modify other batteries to work in a Prius however most will cost about the same as the OEM battery.

 

The procedure in the owner manual is correct. Use the underhood jump point. Never, ever short the positive and negative jumper cables or your Prius could need thousands in repair costs

A lot of people like to "test" their jumper cables by briefly touching the pos and neg clamps once the car is hooked up. They get a little spark. That should never be done on any modern car, you could destroy the computer. On the Prius it can destroy a lot of components

The battery is an odd size, think motorcycle or lawn tractor. It's sealed with a provision for a vent tube. Apparently a Mazda Miata battery can be adapted to work

 

Jayman and I may be saying the same thing. But the warning I want to state is *never get the jump cable polarity reversed* If nobody at the scene can be 100% sure they are correct, get smarter help!

At a minimum you will kill an expensive hard to replace fuse block that the Prius can't run without. At worst an ECU or two.

It may be common for ECU-rich cars to be this fragile, I do not know. But Prius certainly is.

 

It amazes me that we even see reports of reversed polarity. I've never had to jump mine, but after first reading a report of improper jumping, I peeked at the under-hood terminals to know what I needed to look for. It should be a no-brainer; the terminals are clearly marked. But then I guess sometimes we unwittingly call on people with no brains to help us with our cars.

 

yes
and if there is no color marking then the + is ticker/wider then the -

 

Yep. I was also talking about idgits out there who will purposely touch the pos and neg cables to make a spark, to "test" the connection. You'd be surprised how often that happens.

Considering how expensive any potential repairs could be, a jump start box is pretty cheap. If it fries, you're only out $80 or so

 

Toyota missed a great chance to help make the Prius more bullet-proof.

Since the 12V battery doesn't power a starter, they could have put a 50 Amp diode between the jump terminal and the rest of the car. That way, if the polarity was reversed, nothing would happen. Alternators have 50 Amp diodes in them, so they're neither expensive or large.

It would also prevent using the Prius jump terminal from being used to (try to) jump start another car thereby making sure that you don't pop the 100 Amp fuse that our cars have.

 

Concering polarity, some 'donor' vehicles have black-insulated cables on both (not necessarily OEM...) so if you encounter one of those be sure to identify the chassis ground.

I guess there aren't many positive-ground vehicles on the road any more. That could ruin your day.

Kohnen the diode pritection idea has been discussed before. I can't think of a reason it shouldn't work. It has also been suggested to Toyota via groups like this (and other means).

A person could certainly make their own Prius jumper cables with fuse and/or diode protection. It would not have to be super-thick wire either. At least one person has made their own. Come to think of it, might be a nice Prius-specific accessory. Anybody need a garage hobby business/time-burning idea?

 

I wouldn't put it as part of the jumper cables - I would make it part of the jump stud. Put a large diode with the cathode attached to the Prius' positive jump terminal, and make the anode available for attaching to. Current can then go into the Prius, but can't come out - this would protect against both cable reversal and trying to jump a bigger car off of the (tiny) 100 amp fused path to the battery.

[Yes, I know that the electrons with their negative charge are the charge carriers. For historical reasons, we engineers say that positive charge moves in the opposite direction as the electrons.]