???Question about jumping a Prius???

The 12V is likely toast. If it doesn't keep a charge after slow charging and then after running for a while, start looking for a replacement.

BTW, all this jumping and charging, make sure you don't cross connect. That's a very bad thing.

 

There is no charging the main battery from the engine compartment. Be careful you don't do any damage to your friend's car.

Time to contact your friend and let them direct you on further action. They must have changed the 12v battery in the past due to the age of the car at least once.

 

The charging rate is VERY low in the Prius. So 15 min is not going to do much. Also do not rev the 2nd car when you do the jump and NEVER-NEVER-NEVER cross connect the cables ($1,000+ damage).

But, it's probably time for it's 3rd or 4th battery.

 

now when we talk about the 12v battery, we mean the little 12v car battery in the trunk, not the hybrid battery(also called High voltage/HV battery, Traction battery, battery pack, main battery).

 

The 12v battery in the trunk needs a full charge. It may no longer be good, but the first thing is to determine that.

You can either place a trickle charger on it overnight (my suggestion), or remove it and take it to a battery shop for a recharge. They may charge a fee, and they may tell you the battery is an ex-battery. A discharged battery develops sulphates on the lead surfaces. This coating prevents the reaction that produces electricity. A slow charge can remove some of it, but not always enough. It really may be actually dead by now. Be prepared.

When jumping a battery from a second vehicle, remember that the leads go positive to positive and negative to negative. It is perfectly fine and usually desireable to increase the engine speed of the donor vehicle. Alternators don't provide much of a charge at all until 1500-1800 rpms. I hold my engines at 2000 rpms when jumping. Try to start right away, if it doesn't work wait another three minutes and try again. Repeat. Don't use any electrical items on the dead car while all this is going on. Turn everything off to not waste any charge.

After the vehicle is successfully jumped and running, 15 minutes of slow driving is worthless. You would want to drive on the open highway for 30-45 minutes minimum, in my opinion. Either that or drive home and put the battery on the charger. Everyone with a car should have a trickle charger to put on a battery overnight. I have two. The brand I recommend is Battery Tender. These can be found at any motorcycle shop, many parts stores, and Wal-Mart has some other brand for boat batteries.

 

"When jumping a battery from a second vehicle, remember that the leads go positive to positive and negative to negative. It is perfectly fine and usually desireable to increase the engine speed of the donor vehicle. Alternators don't provide much of a charge at all until 1500-1800 rpms. I hold my engines at 2000 rpms when jumping. Try to start right away, if it doesn't work wait another three minutes and try again. Repeat. Don't use any electrical items on the dead car while all this is going on. Turn everything off to not waste any charge.

After the vehicle is successfully jumped and running, 15 minutes of slow driving is worthless. You would want to drive on the open highway for 30-45 minutes minimum, in my opinion. Either that or drive home and put the battery on the charger. Everyone with a car should have a trickle charger to put on a battery overnight. I have two. The brand I recommend is Battery Tender. These can be found at any motorcycle shop, many parts stores, and Wal-Mart has some other brand for boat batteries."


The dead battery is in a PRIUS. Therefore, there's no need to rev the donor's engine. In face, you don't even need an running engine. All you need is hook up the jump cable properly and that should be enough power to boot up the Prius computer and activate the relay for the traction battery. Once the READY light comes on, the jumper cable could be unhooked. You don't even need to drive the Prius, just let it sit there for a few hours.

 

Paraphrased…
1. Connect jumper cables as previously described by Mr Incredible.
2. Start the engine of the second vehicle. Increase the engine speed slightly and maintain that level for approximately 5 minutes to recharge the 12v battery of your vehicle.
3. Vehicles without a smart key maintain the engine speed of the second vehicle and start the hybrid system of your vehicle by turning the engine switch to the ON position.
Vehicles with a smart key system maintain the engine speed of the second vehicle and start the hybrid system of your vehicle by turning the POWER switch to the ON mode.
4. Make sure the READY indicator comes on. If it does not, contact your Toyota dealer.
5. Remove jumper cables in the reverse order of placing them.

 

A typical 12v car battery could provide 50 amps for at least 30 seconds. That's ample of power to boot the Prius computer. No need to run the engine of the second car.

Once the READY light is on, the traction battery will take over and start charging the Prius's 12v battery. Jumper cables could be removed at that point. There's no need to drive the Prius unless you wanted to. You could just let the Prius sit there for a couple of hours. The ICE will start automatically when the traction battery runs low.

The bottomline is that you don't even need a second car. You just need a fully charged second 12v battery along with a jumper cable. The Prius does not use the 12v to start the ICE. The 12v is just for the electronics.

 

Having not jumped a Prius, I couldn't say what a real world event would look like.

But having jumped a multitude of dead regular cars, I can say that simply having a battery to jump off of would not work in the great majority of cases. Increased RPM and time are required almost always.

Having an older Prius, you may have had to jump it. Is this the case or are you merely citing theory?

 

The Prius is not a regular gas car, it's a hybrid. I'm speaking from experience, not theory. The Prius uses the traction battery to start the ICE, and that battery is huge in size and power. You should never mess with that battery. The 12v battery is for powering the computer and it doesn't need a lot of power to boot up the computer. Once the computer is booted up, the car should be able to run itself. If it doesn't, you may have bigger problem than a dead battery.

 

I fully and completely understand what you are saying. Is the one battery, no car sufficient to boot the system to start the car? I believe it might, but would add that it does not appear to be guaranteed if the factory manual suggests increased RPMs and time. Perhaps they think it important to drive away with some backup charge.

Not trying to be argumentative, only to find out how real world Prius jumps work.

 

Does the factory manual state that? Which one and where? It's no secret that the 12V only turns on the electronics and and HV turns the MG starting the car. The risk of introducing excessive or jolting power to the system resulting in costly damage is too high to recommend others do it. I believe I recall it being stated in PC that the system has been jumped with little flashlight batteries. But absolutely a jump from a battery in a donor car with that car off is enough to turn on the electronics so the HV battery can run the system.

 

I copied it out of the C manual .pdf.

I have no idea what your manual says.

What does it say?

 

Checked my manual. You are correct. My bad. It does recommend the donor car be running at 2,000 rpm's for five minutes while the donor battery is connected to the discharged car before placing it in Ready mode. I suspect in most cases this is not necessary but would depend on how dead the battery is and that is what it says. It's also true that once the system is in Ready mode it doesn't have to be driven to be charging. The ICE will cycle on as needed.

 

I still disagree with the revving. My gas-only van produce 14v across the battery without revving. There's no need to rev just to power up the Prius computer. If one choose to leave the cable there for 5 minutes, I'm not going to fight that but revving is really not necessary.

 

I would think its more about amps than volts, but with a depleted battery the input voltage may not be be as needed.

 

Been jumping cars for 50 years plus and always have used the donor revs method and waited a few minutes before starting the dead car. Only once it didn't work and AAA had to use a special charging vehicle with a 24 volt battery circuit they claimed. I've always carried heavy duty extra long expensive cables and been the donor many times.

I figure if I wanted to I could always RTM before doing it with the Prius to see if it could even be done. Maybe flag down a normal car and use my jumpers if I couldn't.

 

I hooked a 2000 watt inverter directly to my van's battery and pulled 1100 watt for 15 seconds, I did it without revving the engine. The 12v battery in the Prius is only use for booting up the computer and activate a relay. All you'll need is a fully charged second 12v battery. You wouldn't a second car.