When a jumpstart goes wrong? Safety Question

Neighbor tried jumping my wife’s ‘06 Nissan Altima, we left it for 10 minutes and came back and the cables had melted through the headlight of both cars and some of the bumper. I wasn’t there but thankfully they stopped their car and were able to disconnect the cables without incident. We noticed after there had been mice living in around her engine from the mouse poop, minimum the last two weeks. What causes jumper cables to do this? Something a rodent may have chewed? Definitely an issue with my wife’s car. Our poor neighbors have a newish midsized suv. My wife has also had constant issues starting her car, even with a new battery I got a year or two ago. Anyone seen this before?

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598

u/Oh_MyGoshJosh Dec 31 '23

My guess is the clamps were switched around

196

u/jhwalk09 Dec 31 '23

Neighbor who did it insists the cables were clamped right, I’m inclined to believe him he’s a handy guy, but thats what it looks like right?

251

u/MarsRocks97 Dec 31 '23

Tight isn’t the issue. Each clamp MUST be clamped to the correct polarity. Mismatching will cause the cable to overheat and quite likely also ruin the weaker battery possible both batteries.

99

u/jhwalk09 Dec 31 '23

That’s what I meant he insists he clamped em to the right ones, black to black red to red

69

u/t3sl1 Dec 31 '23

Red dead battery to red live battery, black live battery to unpainted metal surface or engine block of dead car battery

10

u/chickenCabbage Dec 31 '23

Why does the order matter?

38

u/t3sl1 Dec 31 '23

if you connect the negatives first then you run a risk of shorting out the batteries if you bump the chassis with the positive cable

16

u/MarsRocks97 Dec 31 '23

This and also you get larger spark/arc connecting positive last.

6

u/chickenCabbage Dec 31 '23

The spark doesn't change based upon the order of connection, it's the same voltage :)

7

u/MarsRocks97 Dec 31 '23

It really does change. This has been studied extensively and is one of the reasons for the order of connection of cables.

7

u/Breadmash Dec 31 '23

I believe faulty car batteries can also cause flammable gas releases when charging - so removing the spark from the battery area by connecting the final lead to the chassis removed the potential for ignition.

3

u/JFrankParnell64 Jan 01 '24

This is the correct reason that the order matters.

2

u/[deleted] Jan 01 '24

Superstition if I ever heard one. Do you think you can open the hood of a car and have flammable gas remain there long enough to be a danger? People should connect the clamps to the posts as the engineers intended, because they can take the amperage. The ground strap may not.

1

u/Breadmash Jan 01 '24

It's definitely true that the battery produces hydrogen when charging, and a faulty one may leak it. Surely the ground strap would be useless if it couldn't take the power of a short and just burn up? And a handful of cars come with an engineered charging point on the chassis for a negative terminal, so wouldn't the engineers intend for you to place the clamp on that?

2

u/chickenCabbage Jan 01 '24

I work in EE and would love to know more - where did you read this?

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0

u/NuclearDuck92 Jan 01 '24

You’ll only get an arc on the last connection, and you want that to happen away from the battery. This is why you connect the black of the live battery to an exposed ground of the dead car.

1

u/[deleted] Jan 01 '24

More fun that way

1

u/tOSdude Jan 01 '24

This is superstition at best

1

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1

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1

u/chickenCabbage Dec 31 '23

That's a good point, tbh.

2

u/TheOnlyCraz Dec 31 '23

I believe it's because electricity flows in one direction? (Correct me if Im wrong) and also so you don't dead short either battery/electrical system when you've got 2 jumper cable clamps on one battery and 2 loose clamps in your hand.

1

u/chickenCabbage Dec 31 '23

Avoiding the 2 loose clamps is a good idea and that's probably the reason, but the electricity flows in a circuit - in both directions.

11

u/Previous-Sympathy801 Dec 31 '23

Batteries are DC supplies, current flows from the negative terminal to the positive.

The order only matters because, if you connect the last clip to the battery terminal it can arc. Car batteries off put a flammable gas, which can be ignited by the arc. It is unlikely but that is the reason.

(I’m and Electrical/Computer engineer)

1

u/chickenCabbage Dec 31 '23

I'm an electrical engineer as well, I know the polarity is important, I was wondering about the order of connection. Reading up on it, lead-acid batteries can release hydrogen, so you'd want to create the spark away from the battery. The engine block or the chassis next to the battery wouldn't do any good, you want to hook that up below the battery (hydrogen rises up quickly) and not too close.

3

u/TheOnlyCraz Dec 31 '23

You may be correct, but it was my understanding that's one of the differences between AC and DC currents, where in DC the direction stays the same, and in AC (such as house voltage) switches direction multiple times a second (hence 60hz in the US)

Like I said I could be wrong, it's happened before.

2

u/chickenCabbage Dec 31 '23

Ah, yes. The polarity (red to red, black to black) does matter, the order in which it is done does not.

1

u/Previous-Sympathy801 Dec 31 '23

You are correct.

AC is alternating current.

DC is direct current.

DC current goes negative to positive. AC the current switch direction X number of times per second. In the US it is a 60hz system, meaning the current switched direction 60 times a second.

Cars are DC

1

u/TheOnlyCraz Dec 31 '23

Thanks for the confirmation!

I believe the 60hz could be visible with my flux core arc welder from harbor freight, about 60 times a second you get cool splatter!

1

u/Z3400 Dec 31 '23 edited Dec 31 '23

The battery is DC, but cars are AC. The battery is only used to start the engine, once running the alternator is running the car and recharging the battery for the next start.

Edit: after a quick google because I questioned myself, it appears alternators are 3phase ac, but rectified so the car is actually still running on dc. Neato.

1

u/81optimus Dec 31 '23

The alternator produces AC but this is then rectified back to DC in order to power the car and recharge the battery. Predominantly the car is DC

1

u/Z3400 Dec 31 '23

You were probably typing that while I was editing my post lol. I typed my comment, then remembered how many times I have seen people argue about it and googled it, then added the edit.

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1

u/porchprovider Jan 01 '24

This argument is as old as Tesla vs Edison.

1

u/SquishyBaps4me Jan 01 '24

You are correct, dc only flows in one direction. It's the only difference.

1

u/Pinksquirlninja Jan 02 '24

DC -> direct current

AC -> alternating current

So yeah something along those lines. AC current can move back and forth, which is why people with solar panels can “sell” any of their excess electricity production to the power grid.

1

u/SquishyBaps4me Jan 01 '24

DC does not flow in both directions.

1

u/Murky_Might_1771 Dec 31 '23

Preventative in case any flammable gas nearby

0

u/TurloIsOK Dec 31 '23

This is the way

1

u/Previous-Sympathy801 Dec 31 '23

The ground to unpainted surface doesn’t matter for which car you do it on. You just need to make sure the last terminal you connect is to an unpainted frame piece.

You don’t not want to arc to the battery terminals.

4

u/IHaveNoAlibi Dec 31 '23

It actually does matter, although not so much as it used to.

A dead battery, when it starts charging, releases hydrogen gas.

The explosive kind.

Your last connection should be to an engine ground, away from the battery, so that this hydrogen isn't being released anywhere near the connection, which sparks.

This should also be the first connection removed, for the same reason.

Modern, sealed lead acid batteries reduce this problem a lot, but they can still bleed hydrogen if there's a slight seal leak.

1

u/[deleted] Dec 31 '23

Dude I’ll be honest I don’t think anyone really does it that way. I’ve jumped, a LOT of cars and never done that. Black to black red to red. Keep it simple.

1

u/HelloMitahChen Jan 01 '24

I memorized for myself:
"Positive, Positive, Negative, Negative"
"Bad, Good, Good, Bad"
to remind myself the sequence of the wires for proper connection.

and it's best if the last last cable (Negative on Bad Battery) to be connected to a ground honestly...

1

u/miket439 Jan 01 '24

Same as “righty tighty, lefty loosy. Also, you want the jumper cables to be the thickest gauge and length possible. Just like a penis, according to my ex-wife 😂

227

u/amazinghl Dec 31 '23

He might think he did it correctly but evident suggest otherwise.

76

u/stevey83 Dec 31 '23

Have you ever put cables on on wrong polarity? If so you’ll realise this wouldn’t have caused this. You wouldn’t be able to ignore the sparks! More than likely the cable was too thin and overheated and melted.

14

u/patti222 Dec 31 '23

And your nose must be broken if you can't smell the magic smoke

7

u/ordinaryuninformed Jan 01 '24

If you ignore the sparks, you get surprising results though

4

u/stevey83 Jan 01 '24

Racing stripes on your headlights !

1

u/Vickyelotes_FUDG Jan 01 '24

Shocking results

1

u/VeryGoodBuddySir68 Jan 01 '24

If you put the cables on while both vehicles are turned off it’s very possible for someone to put them on the wrong way around and not notice a thing

2

u/stevey83 Jan 01 '24

Electric is electric. Doesn’t matter if the engine is running or not. Try it sometime!

1

u/clvnblnkee Jan 01 '24

Some people assume the big sparks are normal and keep it clamped on. The cables will become the heating element.

1

u/Mammoth-Snow1444 Jan 01 '24

I accidentally touched a ratchet handle on the POS lead to the body. I'll never use a ratchet again on a battery terminal. That was scary I couldn't imagine seeing all those sparks and saying send it

1

u/stevey83 Jan 01 '24

Did it damage your ratchet. I’ve seen it do damage before!

1

u/Mammoth-Snow1444 Jan 01 '24

It left a mark and was really warm. My tools are beat up to begin with though.

22

u/Innit2winnit23 Dec 31 '23

Could have been weak jumper cables too

1

u/johnny_briggs Dec 31 '23

They been have to be fit for purpose though right? Otherwise we'd see lots of these posts.

6

u/Business_Welcome_709 Dec 31 '23

No

Smaller gauge wires are sold sometimes and don’t provide enough flow to sufficiently jumpstart

1

u/johnny_briggs Dec 31 '23

I stand corrected, ty.

2

u/Business_Welcome_709 Dec 31 '23

You’re welcome

In that case yes , they will start to overheat due to overvoltage. Witnessed it when jumping a civic from a Chevy Avalanche one time, with jumper cables sold in a “trunk emergency kit”

2

u/Styrak Dec 31 '23

Overcurrent (amperage). It's all the same voltage (12-14v).

1

u/Business_Welcome_709 Dec 31 '23

Thanks

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u/DeleteMyOldAccount Dec 31 '23

I’ve had this issue, but only on much larger rigs with much higher crank requirements. This is a baby Altima?

1

u/DeleteMyOldAccount Dec 31 '23

I guess OP what kind of vehicle was doing the jumping?

1

u/Business_Welcome_709 Dec 31 '23

He said it was a larger newer SUV, still should only be 14.3v nominal

Doesn’t say anything about the jumper cables though

An awful lot to speculate about without seeing the entire electrical system

3

u/DeleteMyOldAccount Dec 31 '23

It’s New Year’s Eve and I’ve got nothing better to do BUT speculate on internet posts while in this airport 🤌

1

u/Business_Welcome_709 Dec 31 '23

Fair enough 😂😂 I’m enjoying the weekend off and recovering from an injury, vaping weed

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u/ballinb0ss Dec 31 '23

I'm sure you know this by now with the traction of this post, but wires don't melt like that unless there's a short which would be the poles reversed on that battery. Everyone does it at least once jumping a car and most people won't admit it. Unless you are very comfortable with electrical troubleshooting, take it to a good shop maybe an electrical specialist shop or dealer. The entire electrical system could be at risk.... anything connected to that battery could be melted like those cables. Or, a fuse/fuse link probably blew and saved everything.

1

u/FlamingButterfly Jan 01 '24

Could the cables be faulty?

50

u/MarsRocks97 Dec 31 '23

Doubtful. I’ve seen this before and it was definitely mismatched. There is a slight possibility that battery cables were replaced with wrong color. I saw this once in an old 70s truck. But it just doesn’t happen to modern cars as these cables don’t corrode away like the old ones used to. Either way, never trust the color clamps on the battery. Always double check that it + positive to +positive and -negative to -negative.

45

u/f0rcedinducti0n Dec 31 '23

Donor positive to recipient positive, donor negative to recipient ground.

Engine ground or chassis ground preferred, not directly to negative terminal.

11

u/NotMoose5407 Dec 31 '23

This is what I learned. I will also double check every time I use jumper cables just to make sure.

1

u/emmejm Dec 31 '23

Same, I worry so much that I always check my knowledge every single time!

1

u/Suds08 Dec 31 '23

I always also double check to make sure I don't accidently hook up the wrong cable to the wrong terminal and have somehow not once but twice blew the fuses on my boat engine from accidently hooking the wrong cable to the wrong terminal on my boat battery lmao now I always quadruple check and still get scared I'm gonna mess it up. I'm just not cut out for charging batteries I guess

1

u/YourInMySwamp Dec 31 '23

Huh. I thought it was recipient positive to donor positive, donor negative to recipient ground.

2

u/AtheistSloth Dec 31 '23

negative should go to ground regardless, right?

10

u/YourInMySwamp Dec 31 '23

You can put either negative to ground or negative to negative. It doesn’t really make a difference. Putting it negative to ground gives you marginally better safety because of less likely spark occurrence.

1

u/stuckels8 Dec 31 '23

That's exactly what he said

1

u/YourInMySwamp Dec 31 '23 edited Dec 31 '23

I am like 90% sure he edited it and that previously it said “recipient ground to donor negative”. You can see another response to my comment where somebody was asking for clarification on if negative should always go to ground. Maybe I’m just stupid though lol.

1

u/oatsssss Dec 31 '23

"recipient ground to donor negative" and "donor negative to recipient ground"

Are the same thing tho right? Or you mean to emphasize the order so ground is connected first so it's not loose to accidentally hit something while it's connected to the negative terminal?

1

u/YourInMySwamp Dec 31 '23

Yes exactly! I was emphasizing the order that they are connected. As far as I am aware the circuit will work regardless of the order but the jump is more efficient and quick when done in the recommended order.

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u/f0rcedinducti0n Dec 31 '23 edited Dec 31 '23

I didn't edit it. You can't edit a post in any way after a reply without getting an (*), like your post has.

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u/YourInMySwamp Dec 31 '23

I don’t think it would be insane lol people edit their comments literally all the time. Sorry I misread it though, was early in the morning for me. A lot of people have jumped a lot of cars it’s basically the easiest thing to do when it comes to car trouble.

1

u/f0rcedinducti0n Dec 31 '23

Look up.

🙃🙃🙃

1

u/YourInMySwamp Dec 31 '23

Where do you see the star? If that’s a browser thing I’m on mobile. I had no idea that was a thing lol

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u/frummel Dec 31 '23

Last week I jump started my neighbour's VW Transporter Mark II and I initially got somewhat confused on the polarity as both battery connected cables where black. Luckily polarity was simply visible by the + and - signs on the battery itself.

0

u/Aint_Shook98 Jan 01 '24

The wire doesn’t know what colour it is so you could put red on black and black on red and as long as it’s the same on either side it will act the same. Cross matching the termination is what would cause issues

1

u/Harryisharry50 Dec 31 '23

Best thing I heard today . I always check the battery for positive and negative terminals seen it too many times wrong color clamps on the cables on the car going to the battery . They do that shit with airlines on semi too one of the lines will break . Oh we only have a blue line to put where there should be red line . Red line the one that releases the brakes on the trailer blue is service brakes

21

u/Joiner2008 Dec 31 '23

As a guy who went to tech school for diesel and auto, who does his own repairs, who has done half a dozen fuel pumps, a timing chain, a few head gaskets, etc. I once hooked my jumper cables up to my Jetta wrong. We all fuck up at some point. It has opposite sided terminals on the battery and the positive is brown. The jumper cable sheathing started to melt but I was there and saw it happening. This IS the reason this happened to your car, your neighbor doesn't want to admit he fucked up something this simple.

2

u/Innit2winnit23 Dec 31 '23

And it's not out of reach to overlook a battery sitting the opposite way in one car than in the other then while red is on the left in one and the right in the other and you never gave I a second look before putting red on the left the 2nd time and now your headlight is wearing a bit of an eyepatch

1

u/Joiner2008 Dec 31 '23

Yeah. I'm used to GM where red is on the right. The Jetta battery is parallel instead of perpendicular, the positive is on the opposite side, and this is the color of the cable:

https://www.ebay.com/itm/276048899771

1

u/Innit2winnit23 Jan 01 '24

Yup that'll fuck you up if you're not paying attention! Complacency kills!

2

u/MrSuperheterodyne Dec 31 '23

I've done it too. Like yourself, done it a hundred times before with no issues. This one day though I must have had something on my mind.... No harm done but my cables melted.

1

u/Joiner2008 Dec 31 '23

I was spooked, my truck's gauges ran crazy for like 2 miles and then went back to normal. Completely ruined the battery in the Jetta and in the truck

6

u/rdmille Dec 31 '23

I did this once, and I am very handy.

Under certain types of lights, the colors of the jumper cables become distorted, and you can't tell the difference. (Think being color blind with red/blue-green cables) Ever since, I use a flashlight to verify the colors.

1

u/UberNZ Jan 01 '24

That's a good point. Especially in dim light, red appears black, as a consequence of the Purkinje Effect. He noticed in 1819 that his favourite red flowers appeared black on nighttime walks.

6

u/MuslimCarLover Dec 31 '23

Nah if he managed to melt through the headlamp cable then he must be colourblind. You need a new battery and headlamp wire set because of it

1

u/HondaDAD24 Dec 31 '23

Don’t forget the bumper melted as well.

1

u/MuslimCarLover Dec 31 '23

Tell me that car doesn’t have parking sensors

6

u/GeeMcGee Dec 31 '23

But that’s incorrect lol… see…

LPT: Know how to jump a dead battery correctly. It's NOT just red to red, black to black.

You don't connect the black cable to the negative terminal on the dead battery.

Take out your jumper cables.

Place both vehicles in Park or Neutral and shut off the ignition in both cars. Engage both parking brakes as well.

Attach one of the red clips to the positive terminal of the dead battery. It has “POS” or “+” on it, or it’s bigger than the negative terminal.

Attach the other red clip to the positive terminal of the other car.

Attach one of the black clips to the negative terminal on the other battery.

Attach the last black clip to an unpainted metal surface on your car that isn’t near the battery.

Start the working vehicle and let the engine run for a few minutes.

Try to start your vehicle.

https://imgur.com/VLq4TBr

Your neighbour created a short circuit and well they get hot

1

u/Ginkpirate Jan 02 '24

This.

2

u/wolfman86 Dec 31 '23

Red to red, black to solid earthed metal….engine block, body work, or similar.

4

u/yorkshirepuduk Dec 31 '23

28 volts @ nearly 200 amps ye when its started take off the leads

-1

u/jhwalk09 Dec 31 '23

Yeah but I don’t think they ever started my wife’s car

3

u/f0rcedinducti0n Dec 31 '23

Look dude, I can tell you as an engineer. Jumper cables are going to be 4 gauge or 6 gauge, and to melt them, the only way would be a short to ground. Starting the recipient car while connected will not cause this.

8

u/BAS316 Dec 31 '23

Your cables may be that thick. I know mine are. I've also seen cheap ass sets for sale and in use by various people that are not. I think the worst one I've seen said 10 or 12 gauge wire.

6

u/voucher420 Dec 31 '23

I could see a cheap set of jumper cables doing this.

1

u/IHaveNoAlibi Dec 31 '23

If they're trying to actively start the car with them, yes.

If they're just letting the battery charge through them, no.

It seems reasonable to assume that when they left it for a few minutes, and came back to it melted, it means they weren't actively trying to start it.

1

u/voucher420 Dec 31 '23

Depends on how dead the battery was or if it was internally shorted. When you hook up two batteries together, they will transfer energy from the one with higher voltage to the one with lower voltage until they equal out. With lead acid batteries, the more they are discharged, the more current they will take. As they come closer to a full charge, they will not be able to draw as much current.

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u/YourInMySwamp Dec 31 '23

I’m not sure what mine are but I bought them from 7/11 when I was in a pinch recently and I highly doubt they’re that thick

1

u/f0rcedinducti0n Dec 31 '23

12 gague wire would be a little anemic for cranking. However if you let it charge for 15 minutes and disconnected before cranking, it would work fine.

1

u/BAS316 Dec 31 '23

Never said they wouldn't work. I personally wouldn't trust them though.

0

u/Prize-File-3719 Dec 31 '23

^{^{^{^{^{^{^{^}}}}}}}

0

u/Ginkpirate Jan 02 '24

I have 1 gauge. Welding cables I put leads on

1

u/f0rcedinducti0n Jan 02 '24

the clamps would probably melt first.

0

u/Ginkpirate Jan 02 '24

What are you talking about? It's being hooked up to a battery to jump-start semi,dump trucks, heavey equipment, and cars. Claiming to be an engineerI thought you would appreciate and understand, but i feel like you wasted your money on a degree. Bigger wire less resistance. It's pretty simple. How are clamps melting?

1

u/f0rcedinducti0n Jan 03 '24

What are you talking about? It's being hooked up to a battery to jump-start semi,dump trucks, heavey equipment, and cars. Claiming to be an engineerI thought you would appreciate and understand, but i feel like you wasted your money on a degree. Bigger wire less resistance. It's pretty simple. How are clamps melting?

IF YOU SHORTED A 1 GAUGE WIRE IT IS SO FUCKING THICK THAT THE ACTUAL CLAMPS WOULD PROBABLY MELT FIRST.

ENGLISH IS HARD, HUH?

1

u/Ginkpirate Jan 03 '24

What the hell? I'm talking about jumper cables not shorting anything out. Reread what I originally said to you. I made my own jumper cables.......with welding cable..... your acting like a 🤡

1

u/f0rcedinducti0n Jan 03 '24

What the hell? I'm talking about jumper cables not shorting anything out. Reread what I originally said to you. I made my own jumper cables.......with welding cable..... your acting like a 🤡

I see I need to slow down and explain this to you;

a 0 gauge wire has 53.5 mm² cross sectional area.

THE ACTUAL FUCKING CLAMPS YOU ATTCHED TO THEM DO NOT HAVE ANYWHERE NEAR THAT CROSS SECTIONAL AREA THROUGH THE ENTIRE CLAMP AND IS ALSO MAKING CONTACT IN A FEW DESCRITE POINTS ON THE BATTERY TERMINAL.

So, in the event of a short, the thinnest sections of the conductor (cable and clamps together) will melt first. It'll start with the alligator teeth on the clamp and them the thinnest section of the metal between there and the pivot of the clamp.

What don't you understand?

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u/evoke3 Dec 31 '23

Why didn’t they?

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u/oh-go-on-then Dec 31 '23

Because they put the clamps on the wrong terminals

2

u/International_Body44 Dec 31 '23

Black to ground.. not black to black .

1

u/FirstWoodpecker2197 Dec 31 '23

If you're jumpstarting it's red to dead black to ground...

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u/[deleted] Dec 31 '23

[deleted]

23

u/Contristatus Dec 31 '23

the negative terminal and the chassis are continuous, it's the same amount of current both ways (as long as the polarity is right) but using a chassis ground eliminates the small chance of a spark igniting the gasses produced when charging a battery

-13

u/GrumpyDumping Dec 31 '23

Connecting the two sets of battery terminals together wrong could cause a dead short (an electrical circuit with lots of amperage but very little resistance), cause sparking, melt your jumper cables and possibly damage [the batteries and electronic systems of both vehicles.

https://www.familyhandyman.com/project/how-to-jump-start-your-car-safely/#:~:text=Connecting%20the%20two%20sets%20of,electronic%20systems%20of%20both%20vehicles.

15

u/jepulis5 Dec 31 '23

Are you AI-based or is your reading comprehension really that bad?

6

u/evoke3 Dec 31 '23

Dude just absolutely destroyed himself. He could have found countless sources saying to connect to ground but he chose one that specifically says he is wrong.

11

u/MarsRocks97 Dec 31 '23

Wrong. Connecting to the chassis is effectively the negative so the exact same circuit is achieved. The car has no true ground. Only two poles and the negative terminal is “grounded to the chassis”. But again this effectively makes the chassis one big - negative pole. The only reason connecting to the chassis is recommended is that any spark produced at connection or disconnection is distanced from the battery. Batteries vent off the top and this is a risk because of the flammability of the hydrogen/oxygen gasses being released while charging. On dead batteries it’s not an issue since you should just be jump starting and immediately disconnecting the cables before gasses begin to form.

Lastly, connecting to the chassis on modern cars is also becoming much less practical as the prevalence of plastic coverings and fully painted engine compartments means there is rarely a good connection or access to chassis point.

4

u/scalyblue Dec 31 '23

The reason you do this has nothing to do with current and more to do with avoiding arcing around the cube of acid spewing out flammable hydrogen gas

3

u/NonEuclidianMeatloaf Dec 31 '23

This is incorrect.

From a circuit perspective, negative to negative and negative to ground are the same thing. The only reason people say negative to ground is because, in the old days, aging batteries tended to leak hydrogen gas during the process. This could start a fire if your jumper cable sparks.

But no, + to + and - to - is otherwise completely safe and otherwise indistinguishable electrically from the perspective of your battery.

2

u/jhwalk09 Dec 31 '23

Thank you for the edit! Ok, so the dead negative goes onto the chassis to ground it? This is such a noob thing I think and thank you for pointing it out

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u/[deleted] Dec 31 '23

[deleted]

1

u/jhwalk09 Dec 31 '23

I’m just confused because she’s jumped it several times before in the last year or two and I don’t think she ever cared to ground it then. I have a hybrid rav4 that I’ve owned since 2019 so it’s just been so long since I jumped a car

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u/[deleted] Dec 31 '23

[deleted]

4

u/jhwalk09 Dec 31 '23

Yeah but that article says to just connect the black cable to the negative terminal on the dead car, not the chassis:

“Clamp the black end of your jumper cables to the negative terminal of the vehicle being boosted.”

3

u/jhwalk09 Dec 31 '23

I’m confused, is the negative side of batteries already grounded?

1

u/scalyblue Dec 31 '23

If it’s working, yes, the negative side is usually strapped to the frame

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1

u/jhwalk09 Dec 31 '23

Hey, can you attach an image of what kind of things to clamp the negative on to get grounded? I know they’re everywhere but I just want it to be super clear for myself and my wife

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u/NoDingDriver Dec 31 '23

If you’re not mechanically minded and don’t know how to recognise what is a good ground in the engine bay, then there’s something much better to do.

Instead of risking an unsuitable ground, take the temporary towing eye out of your car’s tool kit, screw it into the front mounting point and clamp the negative to that instead. This is a perfect ground to use and there’s no way of mixing it up with anything else that may damage one of the cars involved.

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u/jhwalk09 Dec 31 '23

My wife just said our neighbor did not turn the car off when she connected the cables, her husband claimed she was better at it than he was… would not turning the car off also cause this?

1

u/NoDingDriver Dec 31 '23

I’ve never seen jumper cables melt like this before, but leaving the car running shouldn’t lead to this happening.

Safe assumption is there was too much electrical load through the cables. Either the car used for jump starting has a battery with much higher Amps than what the jumper leads were designed for or the leads were connected poorly creating a short circuit which kept heating the cables until they melted.

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u/jhwalk09 Dec 31 '23

Thank you!

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u/Azkabacon Dec 31 '23

Just clamp it to the negative post on the battery, ive boosted hundreds of dead batteries always on the negative post and have never had an issue

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u/jhwalk09 Dec 31 '23

Well apparently that’s not what to do, you have to clamp the negative on the dead side to a grounding element

3

u/Azkabacon Dec 31 '23

The negative post is grounded already, the only reason not to clamp it is if it's not easily accessible

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u/jhwalk09 Dec 31 '23

Ok aside from the possible mouse chewing I think this is the answer

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u/Contristatus Dec 31 '23

yeahhh your neighbor messed up and didn't want to admit it

1

u/IHaveNoAlibi Dec 31 '23

/r/confidentlyincorrect

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u/TheGoober87 Dec 31 '23

Did he actually say black to black? Cuz that ain't right.

1

u/Tuques Dec 31 '23

Yea. Never attach directly to the negative terminal. Always attach to a grounded metal part of the chassis. That's like automotive 101....

1

u/Goddamnmint Dec 31 '23

He didn't do it right. It's embarrassing as hell to make that mistake and he doesn't want to admit to it. He's likely just trying to get out of paying for your car's damage.

1

u/Dude-with-hat Dec 31 '23

I mean I could insist I wasn’t an idiot too, but that’s probably what happened

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u/Ziazan Dec 31 '23

You're supposed to do them in a specific order, and the black terminal on the dead battery isn't connected, you connect that clamp to some unpainted metal on the chassis, or the specific point that your car might have for it.

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u/bg10389 Dec 31 '23

There is absolutely no possible way putting them in parallel properly would cause this, he shorted the two batteries in series and heated the wire to the point of melting

1

u/clintj1975 Dec 31 '23

If he has a positive ground vehicle (your Altima is negative ground), and he connected it based on the location of which terminal is hooked up to the ground strap, he 100% got it backwards. You have to check the marking on the battery next to the terminal, which can be covered up in some cases. What does he drive?

The other possibility is the battery on the Altima is completely shorted out, but that's rather less likely.

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u/autodidact-polymath Jan 01 '24 edited Jan 01 '24

OP the type of person that would walk away while jumping two cars for 10 MINUTES is not what I would describe as handy.

No bleeping way I walk away until both jumpers have been disconnected from the battery.

1

u/Aggleclack Jan 01 '24

I know you say that but this kinda screams that he didn’t

1

u/NuclearDuck92 Jan 01 '24

He didn’t. Plain and simple. Leaving them unattended is also kinda nuts. Jumping isn’t charging, you should never need them connected for more than a minute or two at most.

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u/AccomplishedAnt6126 Jan 01 '24

This can only happen from connecting them wrong and creating a short cicut. These cables would have gotten red hot. That won’t happen when they are connected right.

1

u/johnny_boy365 Jan 02 '24

No offense yo ur neighbor I'm sure he is a handy man but who know maybe he did make a mistake and is too embarrassed to tell the truth or it was simply an accident he didn't notice.

1

u/LonleyWolf420 Jan 03 '24

If it wasn't.. youd have at least one blown (MAIN) fuse.. i used to work at Lucky’s and there was a guy they hired that kept doing this.. its not normally something you miss.. theres BIG pops and bangs and LOUD ass arks of electricity and generally at least one cars main fuse pops and wont get any power after..

I do know from the same experience if you have a smaller guage wire and using 2 alternators to charge it gets hot really fast.. never had one melt through the car but had one melt its own casing once.

1

u/elitemarxman Jan 03 '24

I actually had something like this happen to me once and it was red to red and black to black. Fortunately I caught it before it damaged any of the cars but the insulation on the wires started to melt.