How to Jump start?

Well, in this case it was an old ATX computer powersupply. So it also was quite stable at 12V and not the 14+V that a charger gives off.

 

Dr. Egon Spengler: There's something very important I forgot to tell you.

Dr. Peter Venkman: What?

Dr. Egon Spengler: Don't cross the streams.

Dr. Peter Venkman: Why?

Dr. Egon Spengler: It would be bad.

Dr. Peter Venkman: I'm fuzzy on the whole good/bad thing. What do you mean, "bad"?

Dr. Egon Spengler: Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.

Dr Ray Stantz: Total protonic reversal.

Dr. Peter Venkman: Right. That's bad. Okay. All right. Important safety tip. Thanks, Egon.

 

In that case, it won't be much good as a battery charger.

Nominal fully charged battery voltage is 12.6; higher for AGM.
At 12.0, it is only about 25% charged; in many applications, effectively dead.

 

Asked and answered.

FWIW, I'd buy and use one of the pocket chargers discussed earlier.
They'll probably stay charged up enough to boot up a Prius for a long time since Priuses require very little starting current.

If somebody needs a jump start?
Hand your pocket charger to them and stand back.

I've actually used Goofy to jump start several cars, but I understand the risks and I'm not going to perpetuate Prius prudishness by saying "No....you can't use Priuses to jump start another car!"
....because mostly?
You can.
Besides.....it's a work car.



RTFM.
Read the (*) ah....FACTORY manual.

 

If you do jump start another vehicle with the Prius, it'd be best to hook up directly at the battery, not at the jumpstart terminal under the hood. The Owner's Manual specifically cautions against doing the latter. Still, considering the Prius battery size, I wouldn't do it unless it was a complete emergency: a jump pack or another vehicle with bigger battery would be preferable.

 

Good tip buried in the Owner's Manual page 599; "Exclusive jump start terminals ... cannot be used to jump start another vehicle."
Thanks Mendel

I don't think the small 12v Prius battery is the main reason for not jumping another vehicle because the main traction battery will be feeding the small battery 14v when in Ready mode. I just don't want to put my expensive traction battery at risk to provide a jump.

I would tell people that my (wife's) Plug in Prius has a big battery that produces 207 to 650 volts DC and "are you sure your vehicle can handle that?" I heard this one somewhere here on PriusChat.

 

I don't believe the traction battery is at risk, only stuff tied to the 12V battery. Unfortunately, that adds up to more potential cost than mere traction battery replacement.

But telling them the traction battery voltage may be a useful tool to dissuade them.

Given no other choice, I would pay for their service call out of my own pocket before I'd allow my Prius to jumpstart any non-Prius. The service call will be far far cheaper than the potential damage to the Prius.

 

I can imagine that a person asking for a jump from a Prius owner, and being denied, would likely attribute that to the Prius owner being one of those "%^@#% obnoxious, holier-than-thou Prius snobs", technical explanations notwithstanding.

 

My Son's TDI had a parasitic current draw issue and needed a few jumps before I fixed it...and I refused to take the chance with the Prius. Can you jump another vehicle...yes, if like me you know what your doing, but one "OOH Sh-T" on the Prius would be too expensive to risk. Your car, your call.

 

If you're starting a big, conventional starter car, one that's got a battery about twice the size of the Prius one, maybe gonna overload the Prius battery?

 

I assume the prius would be in Ready mode if it was jump starting another car. Then the big traction battery is feeding the 12v battery so it would not easily get overloaded. The down side is that in Ready mode the DC/DC inverter, engine ECU, and traction battery are connected to the 12v and connecting the jumper cables wrong has been known to cause expensive damage.

 

As someone who originally learned jumpstarting just by watching dad and others do it, I must point out that common tribal knowledge about jumpstarting includes numerous improper practices, albeit ones that traditional cars (at least the older ones) have some reasonable immunity. Thus, many people who think they know what they are doing, don't know enough. That point was brought home by my last Ford, which suffered ignition failure shortly after providing its fourth jumpstart.

The Prius lacks much of that immunity, and has vastly more expensive consequences.

If my refusal to provide a jumpstart was leading to serious disagreement, I would actually pay for a stranger's service call or even a tow before I would allow a jumpstart from my Prius. Many jumpstart error stories so expensive, that such a service donation to a stranger seems very cost effective.

 

I never said it was a charger. All I said was that a 150W powersupply will start the car.
I left the charging of the battery to the car.

 

It is not the battery that will overload it but the starter motor.......along with the weak battery trying to suck up a bit of charge too.

NO. Because of exactly what you said, it should NOT be in READY mode.

FWIW, that same good practice also applies to jumping from a conventional car; the "donor" car should NOT be running because of increased risk of damage if a mistake is made. Having been there and done that though, it is real easy to rationalize away that good practice when it is -20 F with a 40 MPH wind.

Did you imply it or did I infer it ??
With that clarification, you are of course right.

 

Do you have any references to your "good practice" of not running the donor car?

I thought standard jumping procedure was to have donor car running because ...
Page 596 of PiP owner's manual, step 4 of how to jump start your PiP; "Start the engine of the second (donor) vehicle. Increase the engine speed slightly and maintain at that level for approximately 5 minutes to charge the battery of your (dead 12v PiP) vehicle."
and
How to jump start a car from wikiHow, step 7; "Start the working car. Let it idle for a few minutes. Do not race the engine, but do rev the engine a little above idle for 30 to 60 seconds. You do this to charge the battery in the dead car - because the starter in the dead car will draw most of the required current (well in excess of 100 amps) from that battery - not through the cables. Common retail jumper cables are not built to pass the current required." Link here; How to Jump Start a Car (with Pictures) - wikiHow

If you are going to jump start a car, you might as well do it according to best practices, which seem to be to have the donor car running to enable its 12v charging system (alternator on normal car, or DC/DC inverter on Hybrid).

I do think the small battery backups with vehicle clamps included should be considered as an optional best practice and I plan to buy one for myself and for my son who has moved out/on for his first job/career at Smuckers in OH.

 

Just 50 years of electronics experience, observing a few bad things along the way and a healthy dose of common sense.

Not knowing exactly what the fault IS with the dead car, connecting it to a good car WHILE IT IS ALREADY RUNNING is a very dangerous thing to do.......for the previously good car.

Making all the connections first and observing no unusually large sparks, then it is probably OK to start the donor car.

But assuming the dead car is in good shape or that it is a hybrid, there really is no need to have the donor running.
A standard size set of jumpers is fully capable of carrying most of the starting current for a few seconds, especially for a hybrid where it does not carry much current at all.

If the dead vehicle doesn't want to fire right off, THEN starting the donor car is a good idea; and then waiting a few minutes before trying again.

 

Toyota thinks different

 

Well said Easy Rider 2.

 

That has been said before.

What you maybe have not considered is that the people writing those manuals are NOT engineers or even mechanics and often things get carried over from previous versions that don't apply anymore.

When jumping a dead hybrid, there should be absolutely no reason to have the donor car running; NONE.
Not even if the donor is also a hybrid. People have successfully "jumped" hybrids with a group of flashlight batteries.

Those instructions are carry overs from conventional cars. And I don't agree with them even then for routine use.

 

There have been too many extremely expensive Prius jump start disasters. Absent definitive failure analyses -- which we are not likely to get -- we are left to guess what really happened. And if it turns out the owner's manual instructions are wrong, the normal consumer isn't going to be able to prove that the instructions are deficient.

Because of that, I insist that any jumpstart I receive be done with a donor supply not exceeding a normal 12V battery. The regular 12V components should never see a supply higher than can be supplied by the HV->12V inverter, and that inverter itself should not get back-biased.

Another Prius, and many traditional vehicles, will be this criteria. But some traditional vehicles will provide too much voltage, due to aging or broken or poorly performing voltage regulators. And you and the donor driver are quite unlikely to know this before the canary in the coal mine dies. The Prius is a canary.