“Don’t use jumper cables!” says Pat Goss on Motor Week.

[PMCErnie]

Poor Pat.

 

[carguy75]

Oh geez Let's skip the details of my career and deal with the second question, which is pertinent to this thread.
You brought up the issue of where cables should be connected when jump starting a car, to avoid "electrical damage" - although you never explained what kind of damage would occur and why. I was simply pointing out that because automotive electronics need to be designed to survive what is known as "load dump", they are much more robust than people think, and not so sensitive that damage would occur if you connected the negative jumper cable to the battery versus the chassis - whatever difference you think that might cause.

Maybe I misunderstood you. Please explain exactly what electrical damage you were talking about, and why it would occur if the negative jumper cable went to the battery rather than the chassis.

The main electrical damage that I "assume" could occur would be to the battery I again "assume" that originates from any spark or discharge that may occur when you first connect the negative battery posts together; maybe a voltage spike as well. The only other components that could be damaged would be the voltage regulator/sensing devices that many modern charging systems have inline with the battery cables and alternator. Possibly other voltage sensitive devices in the car like control modules could be damaged as well. Just a guess on my part, because I never did a proper experiment to see what could actually happen on a newer car between the two jump methods.

To be honest; I have always jump started my older cars with the negative battery terminals connected together without any issues until I purchased 2010 and newer vehicles. Newer cars does seem to have more sensitive electronics components(various control modules and can-bus networks) that could be damaged from any voltage spikes caused by the sudden direct battery connection. Hence, I just connect the negative jumper cable to a chassis ground like instructed in the owners manual for any modern car that I use to jump start any dead battery.

In regards to your career; you opened that door by saying that you designed automotive components while talking about the charging system; therefore you gave the impression that you designed electrical components for automotive charging systems. It is like I am saying that I know everything about medicine because I work in a hospital, not true. The medical field has many specialties; the same for electrical engineering. Hence, I wanted some clarification on what you actually designed. Thank you.

 

[Husky]

Do you understand that the negative terminal of the battery has a very low resistance, direct connection to the chassis? If so, why would you expect that the sudden connection of another battery to one or the other would be more or less likely to result in a voltage spike? What field of electrical engineering is your expertise in?

 

[carguy75]

Do you understand that the negative terminal of the battery has a very low resistance, direct connection to the chassis? If so, why would you expect that the sudden connection of another battery to one or the other would be more or less likely to result in a voltage spike? What field of electrical engineering is your expertise in?

LOL. I work in Radiology. I only have a basic rudimentary understating of electronics obtained through some courses taking over the years many moons ago.

Most information I found about jumping starting car batteries states voltage spikes as an possible incidence when the negative battery cables are connected together if a vehicle have a defective voltage regulator or a spike in voltage from an running alternator, however that could probably happen even when jumping using chassis ground I suppose. That is all I got the matter.

The Genesis models we have do not even have the risk of jumping a car incorrectly anyway unless you directly connect the batteries by going into the trunk or inverted cable connection.

I also think that a good ground is a proper ground whether on the battery or chassis, but I still just jump start modern cars as described in the manuals since I do not know if an voltage spike or any unfavorable incident will occur that could damage vital components in my cars by connecting the batteries directly to each other. However, if you think that you know better than the electrical engineers of modern cars on the proper method to jump start modern cars so be it. I am not qualified enough to say that you are not.

I will still just connect my negative jumper cable lead to chassis ground on any car that needs jump starting if I use jumper cables. However, now a days I just use a jump pack that I store in my trunk over jumper cables.

I do however take back my statement that connecting the negative jumper cable lead directly to the negative battery terminal will cause electrical damage more so than to the chassis ground; since I really have no proof or actually knowledge that it does. Connecting the negative jumper lead to chassis ground is maybe just for safety against sparks igniting battery fumes like mentioned earlier more so than to prevent electrical damage to electrical system.

 

[bthor]

The reason you're supposed to connect the negative (ground) to the chassis, away from the battery, is to prevent the chance of sparks, when connecting it, from igniting any hydrogen gas emitted from the battery under charge.
Also, for cars with trunk mounted batteries, where they put a positive battery post under the hood, they use a chassis mounted post for the negative terminal, rather than having to run another heavy cable the length of the car back too the battery.
As a EE of forty years, I can think of no good reason, from an electrical standpoint, to use the chassis rather than the battery for the negative connection, considering the fact that they are connected by an extremely low ohmic connection (milliOhms).
Also, as someone who has designed electronics for car manufacturers, I can say that there's a lot of misinformation out there regarding how sensitive modern electronics are. Sure, there's a lot more electronics in modern cars and they are certainly more sensitive than light bulbs and motors, which is about all we had in older cars (other than the radio), but electronics designed for the automotive industry are required to work over a very wide voltage range and tolerate various over-voltage conditions for different lengths of time. They are much more robust than many would have you believe.

Finally someone who understands. Side note - do you think its best to jump at battery or connections under the hood? I am leaning towards the battery----? thx b

 

[tarhoosier]

My Miata has trunk mounted battery. No way the positive (or negative) end can go on the battery and the matching clamp can stretch to the engine bay. Unless there is some ground in the trunk of which I am unaware. There is no engine bay alternative connection for this Mazda such as there is with the Genesis

 

[Husky]

Finally someone who understands. Side note - do you think its best to jump at battery or connections under the hood? I am leaning towards the battery----? thx b

I think whichever is most convenient and allows for a good solid connection. However I guess there is some risk, when using the battery for both connections, that a spark could ignite methane gas produced while charging. Although I don't know how likely that is with today's batteries, especially those trunk mounted batteries which are vented outside. I suspect it's one of those long-shots that the lawyers make sure is included in the manual. (Like the instructions "don't drink" on the bottle of bleach - except for COVID of course )
It's also worth noting that even if you do use the chassis for the negative connection, to keep it away from the battery, it's only safer if you connect the ground charging lead last and disconnect it first. If you get the order wrong, you'll still be producing sparks at the battery.

 

[Jhon]

If you use one of those portable chargers, you can hook up the cables before you turn on the power that goes to them. That should solve the spark problem.

 

[Husky]

True, good point! I'm not used to those yet, even though I bought one last year, haha.

 

[bthor]

Genesis G80 Owner's Manual (Page 497 of 604) | ManualsLib

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[Jhon]

True, good point! I'm not used to those yet, even though I bought one last year, haha.

It is one of those things you buy, and if you never used it, thats good too!
Like generator or snow blower.