Admit Nothing

[richard schumacher]

This ugly situation suggests that it would be worthwhile for Toyota to add polarity protection to the jump point. On one hand whomever is at fault it can't be good for Toyota to gain a reputation for selling cars that are easy to damage so expensively. On the other hand no customer wants to risk expensive damage because of a very easy mistake; no matters who pays for it it's still a big inconvenience.

I'd bet that a retrofit kit for the jump point would be a viable aftermarket product.

[lesturner]

Would seem to me that a healthy rectifier on the positive battery lead would completely eliminate the problem. You might be able to smoke the battery, but everything upstream would be protected.

I will see what I can find... I have never (in 30 years) hooked jumper cables up backwards, but the first time sounds like it could be expensive.

Les ---

[Nords]

Originally Posted by galaxee

hey guys, uh, on behalf of the guy who has to figure out what's wrong with your car i'd like to mention that they usually don't get paid much for the time they spend finding out the problem. sure you could conceal a critical bit of information. and sometimes that critical information, once discovered, makes the situation plainly obvious anyway. but at that point the tech has spent a day or so tracing wires and whanot for peanuts when he could have been doing 60k max services that put food on the table. so now he's pissed, and has time to make up for because you could have just told him in the first place...

Fine, then send management out of the room and let me talk to the tech. I'd rather have a conversation about what happened than about what the bureaucracy can't do for me.

I've gone round & round with a service manager (over a brake job) and finally asked to take a tech along for a test drive. 30 seconds after starting the test drive the problem was all better, thanks to the tech and not to the "gatekeeper". Same thing with a transmission noise.

With my experience as a troubleshooting supervisor, I'd hesitate to tell a tech (let alone a service manager) anything that I didn't personally do or directly observe. My comment like "I thought it might be this problem..." can all too often lead someone off the troubleshooting trail, and I have no idea whether that person is someone who has the experience to avoid getting sucked into it.

In a doctor's office, an offhand comment like "Isn't this a cancer symptom?" can cause the doctor to think "Ruh-roh" and to order up a bunch of (technically unecessary) tests to set the patient's mind at ease and avoid potential malpractice issues. Maybe service managers think the same way.

[Scruge]

In all my years of dealing with service work (warranty) I've never had a service writer communicate my problems accurately on a service order.
So I've never made sense of wasting a great deal of time elaborating.

[Patrick Wong]

Originally Posted by richard schumacher

This ugly situation suggests that it would be worthwhile for Toyota to add polarity protection to the jump point...I'd bet that a retrofit kit for the jump point would be a viable aftermarket product.

Keeping in mind that a silicon diode has 0.7V voltage drop when conducting, it may not be a good idea to have the diode in the circuit when the jump is correctly connected. Hence my idea would be to connect the diode's cathode terminal to the current jumpstart terminal, and the anode terminal connected to ground (i.e., a crowbar). Then put a 50A fuse between the current jumpstart terminal and a new terminal, which will become the new jumpstart terminal.

If the jumpstart is correctly done, the diode has no effect. If the jumpstart is reversed, the diode will conduct and pop the 50A fuse.

[Scruge]

Originally Posted by Patrick Wong

Keeping in mind that a silicon diode has 0.7V voltage drop when conducting,

The series diode would be less parts and easier to recover from, rather than replacing fuse for crowbar configuration. I don't think voltage drop across diode is a big concern if all you're doing is jump starting. Starter motors are usually series wound devices and are more current dependent than voltage. Besides the jumper cables usually introduce a voltage drop.
One might consider using a germanium or schottky diode as alternative to silicon, if voltage drop is an issue.

[hiremichaelreid]

Originally Posted by Scruge

I don't think voltage drop across diode is a big concern if all you're doing is jump starting.

"Jump" starting a Prius ? I presume so since I hope we all know jumping FROM a Prius is a big no-no (unless it's Prius to Prius perhaps.)

AFAIK, all the Prius needs to start is enough for computers, sensors, injectors etc. No 100 Amp starter motors; ICE startup is handled by MG2 and the HV battery.

I suspect the needs are 10 Amps or less. So no problem, IMO. Even if voltage was a problem, the 12v donor car can be left running which generally provides plenty of extra voltage over 12; like 13.5-14 or so.

Anyone want to be the pioneer in creating the "Series diode jump protection mod" that Toyota should have put in at the factory... ?

An alternative mod would be a small 12v backup battery on a switch. If the Prius only needs 10 amps or so for a few seconds to be "jump started", then perhaps a small battery pack would be sufficient. And no jumper cables or donor car required. Since my wife will drive at least occasionally, I think I'll do this backup battery mod.

Anyway, I think the existence of, and proving of this mod's protection, would give ammunition to anyone having their Prius held for $5k ransom by Toyota dealers for something Toyota could have probably added for $10 a car.

[misslexi]

Originally Posted by Scruge

The series diode would be less parts and easier to recover from, rather than replacing fuse for crowbar configuration. I don't think voltage drop across diode is a big concern if all you're doing is jump starting. Starter motors are usually series wound devices and are more current dependent than voltage. Besides the jumper cables usually introduce a voltage drop.
One might consider using a germanium or schottky diode as alternative to silicon, if voltage drop is an issue.

Voltage drop is a major concern in a low voltage, high current circuit. And, voltage drop is directly proportional to current; the more current the more voltage drop. I agree that jumper cables introduce further voltage drop, I just don't believe that's any reason to ignore the same in other parts of the jump start circuit.

Patrick Wong's idea is excellent; the diode stays out of the working circuit until a reverse polarity connection is made.

Maybe using a 50A circuit breaker instead of a fuse would strike a good balance between hassle and loss of wallet.

[misslexi]

Originally Posted by hiremichaelreid

AFAIK, all the Prius needs to start is enough for computers, sensors, injectors etc. No 100 Amp starter motors; ICE startup is handled by MG2 and the HV battery.

I suspect the needs are 10 Amps or less. So no problem, IMO. Even if voltage was a problem, the 12v donor car can be left running which generally provides plenty of extra voltage over 12; like 13.5-14 or so.

I think there's some confusion as to where certain posts are contemplating the location of the rectifier.

My understanding is the rectifier location being proposed is between the jump start terminal (which may be imaginary right now) and the battery terminal; not the battery terminal and the vehicle positive lead.

Placing the rectifier in the latter location should protect the vehicle circuits and based on your analysis may be a darn good idea.

It does leave the battery open to reverse polarity mistakes and maybe that's not such a big deal, after all batteries are relatively cheap.

If the vehicle electronics are current sippers as you postulate, there really is no excuse for Toyota to leave them wide open to a reverse polarity error.

[galaxee]

Originally Posted by andyprius

There is no wasted time, car will not start, go to battery. Hybrid or non-hybrid.

but if you apply that universally, and say the problem was some crappy aftermarket cd player you had the next door neighbor's kid install...

that's where you see someone with an axe to grind.

Originally Posted by andyprius

Actually my question was: Has your husband seen signs of arcing, burned marks and possibly partially melted post??? Connecting 12 Volts to ground is called a short circuit and leaves evidence. If: there are no signs, then the jumper connection was in order. Period.

those were jumped on the underhood terminal. there were scorch marks present. but you can get scorch marks if say your headlights are on when you hook up cables, even if you do it right. so scorch marks unfortunately aren't a 100% indicator of anything.