Rethinking Jumper Cables

[JHZR2]

I was thinking about getting my brother a set of jumper cables for his burthday. Its a permanently useful thing that is prudent to have... He encountered a weak battery in his car for the first time this year, so cables shouldn't be needed for a while, but you never know. I was looking at US-made, fine copper, 2 - 1/0 type size, 12-16 feet.

Biggest and longest, right?

In my search, I noted more and more commentary that standard jumper cables are obsolete, if not dangerous to modern cars. The basis was that voltage regulators go unregulated, and there are so many computers in there, that things can and do get broken. Of course, generally after that was a plug for either smart cables or a jumper pack...

So it got me thinking.

1) computers, even body and accessory control computers are not a post 2000 issue, yet many articles blindly define the issue after ca 2000.

2) dont vendors reasonably check and harden their equipment for a range of voltages and scenarios? Perhaps even 24v sources being used to jump a 12v vehicle?

3) dont vendors still often give a jumping post (if the battery is located away from underhood), and some depiction of how to jump the car?

I guess you could blame it on car to car jumping, and say that jumper packs are ok. Of course, in case of a shorted battery, the alternator voltage regulator will still be going possibly haywire, trying to ratchet the voltage up while the battery is dissipating energy in the short. Some things Ive read indicated that the removal of cables will make multi-hundred volt surges that damage things. Ok maybe. But im not sold on it being the voltage regulators.

What everyone leaves out is inductance. L*dI/dt creates a voltage spike, and this is where longer and bigger fails... voltage drop is a consoderation, definitely. But the longer the cables, the more inductance (0.4uH/ft or so, regardless of AWG)... so a 20' set will have a lot more inductance than a 12' set.

I am not a fan of Li-ion booster packs because the heat of a car in summer does not jive with safe storage of batteries. I also dont like that they cannot provide some sustained low-rate charge versus some over-hyped amp/Joule rating that doesnt make sense for the size of the conductors. I find those small lead acid jump packs stupid too... carrry a small starter or even a cheapo tractor battery if thats the desired approach.

I am a fan of keeping an older, marginal battery, if not a newer, cheapest size battery on a float charger as a booster pack if need be. Of course it would be at home, while cables would notionally be in th car... Putting a lone battery in parallel creates no issue other than that the voltage of the vehicle could rapidly drop when booster cables are removed when jumping. But at least there is no other vehicle in the loop.

I think im going to stay a believer in old fashioned, heavy gauge jumpers, with big, copper clamps and high quality copper conductors. But, im going to be more of a believer in as short as practical, and as high a gauge as possible, since it adds no inductance but minimizes voltage drop.

Then, the connect both cars up turned off method is good as far as Im concerned. Yes its slower and you only have the voltage deltas of the batteries themselves (a few volts or less most likely). Just use the voltage deltas to flow charge to the weak battery, and start the bad car wih the two batteries jn parallel to reduce impedance and improve power. I may not ever try to jump a car with the donor engine running again, merely because the risk of inductive spikes is real if a high output alternator and a low source impedance battery allows for a good amount of current flow from battery to battery...

Interested to hear others' thoughts on jumping. Ill admit that im pretty lucky. The last time I killed a battery was 2003, bad diode in an alternator. I did have a shorted cell in a battery in around 2008, could barely jump the vehicle being fed from a tow truck... maintenance is key, to prevent the need to jump... but when the need arises...

Thoughts?

 

[Garak]

Jumping is generally an emergency type assist, where there is quite likely something already catastrophically wrong with at least one component in the recipients electrical system, already. Anecdotally, from the taxi years, the worry was more from the donor perspective than the recipient perspective. A lot of taxi drivers simply wouldn't give boosts (and this was long before 2000), and those that would made sure that the two way radios and other such equipment was all shut down. Even then there could be a whine induced into the donor's alternator when using the two way radio.

Now, I think a lot of the stuff we read exaggerates things. Not only do we have people who want to sell automobile club memberships, smart cables, boost backs, and so forth, but we also have a lot of fear around liability.

Heck, there's a semi-prominent Canadian automotive journalist/mechanic who actually goes out there and states no one should change their own oil, and it should be left to a journeyman mechanic. I don't know of a lot of journeyman mechanics doing the oil changes at the dealer.

There's a lot to be said for working within one's own skill set, provided it doesn't turn us into a bunch of invalids.

 

[ag_ghost]

Interesting post. My initial thought was that "it depends". FWIW, the owner's manual for our 2015 CR-V describes a fairly classical approach:
Quote:
Turn off the power to electric devices, such as audio and lights. Turn off the engine, then open the hood.
1. Connect the first jumper cable to your vehicle's + terminal.
2. Connect the other end of the first jumpercable to the booster battery + terminal.
- Use a 12 volt booster battery only.
- When using an automotive battery charger to boost your 12-volt battery, select a lower charging voltage than 15 volts. Check the charger manual for the proper setting.
3. Connect the second jumper cable to the booster battery - terminal.
4. Connect the other end of the second jumper cable to the engine mounting bolt as shown. Do not connect this jumper cable to any other part.
5. If your vehicle is connected to another vehicle, start the assisting vehicle's engine and increase its rpm slightly.
6. Attempt to start your vehicle's engine. If it turns over slowly, check that the jumper cables have good metal-to-metal contact.

But maybe a 2015 CR-V not modern enough

Kevin

 

[92saturnsl2]

Jumping a dead battery = hook up a 12V source that will allow the starter to spin, start the engine, which in turn causes the alternator to function and run the car.

There's no rocket science to this, and you're making it way too overcomplicated. If you have a shorted cell in your battery, a booster/jump/etc. probably won't help as you're still feeding the short.

New vehicles aren't that different than old. Lots more computers and electronics, but they're still designed to be jump started. The battery acts as a huge capacitor against voltage spikes and such, so it'd be ill advised to disconnect it with only a booster/jumper cable from another car attached. Common sense prevails. Obviously a 10 foot 10 gauge cable is worse than a 10 foot 6 gauge cable. But you already know that...

 

[Leo99]

I don't futz around with older marginal batteries. Once they get marginal, they get replaced.

I'm going to buy a li ion jumper when I see one on sale.

 

[JHZR2]

Originally Posted By: 92saturnsl2
Jumping a dead battery = hook up a 12V source that will allow the starter to spin, start the engine, which in turn causes the alternator to function and run the car.

There's no rocket science to this, and you're making it way too overcomplicated. If you have a shorted cell in your battery, a booster/jump/etc. probably won't help as you're still feeding the short.

New vehicles aren't that different than old. Lots more computers and electronics, but they're still designed to be jump started. The battery acts as a huge capacitor against voltage spikes and such, so it'd be ill advised to disconnect it with only a booster/jumper cable from another car attached. Common sense prevails. Obviously a 10 foot 10 gauge cable is worse than a 10 foot 6 gauge cable. But you already know that...



Kind of missing the point... its not rocket science, yet theres a lot more phenomena that can go on behind the scenes than one necessarily considers at first glance. I believe that cable inductance after the jumpstart is a possible concern, and would be the case of some of the ills that many blogs and pieces online talk about, without necessarily addressing the cause.

Originally Posted By: Leo99
I don't futz around with older marginal batteries. Once they get marginal, they get replaced.

I'm going to buy a li ion jumper when I see one on sale.


Agreed. No substitute for maintenance.

However, some thijgs happen without any prior indication. Bad diode in alternator causing my battery to drain was a random overnight issue. Internal short stranding me on the outskirts of Chicago had no prior indication, including 650 miles of driving that very day. You never know.

 

[wrcsixeight]

Jhzr2

Think Jumper cables jumping modern vehicles could benefit from ferrite chokes and twisted leads, or are such practices only for RFI?

 

[eljefino]

I have a couple sets of cheezy 10 ga copper cables. The alligator clip connection is the current limiting factor, IMO.

They force the user to hook up and charge up for five minutes or so, so the victim's battery gets a surface charge and helps everything out.

I rev the donor car to the moon before trying to start, so the inrush/outrush of current during the *click* of the solenoid is spread across as many of my alternator's diodes as possible.

Still lucky. Or is it technique?

 

[spasm3]

Originally Posted By: eljefino
I have a couple sets of cheezy 10 ga copper cables. The alligator clip connection is the current limiting factor, IMO.

They force the user to hook up and charge up for five minutes or so, so the victim's battery gets a surface charge and helps everything out.

I rev the donor car to the moon before trying to start, so the inrush/outrush of current during the *click* of the solenoid is spread across as many of my alternator's diodes as possible.

Still lucky. Or is it technique?

I like to hook the cables up with the donor car off ( especially if its mine!) once the cables are hooked up, i crank up the donor car and let it charge a bit.

I shut the donor car off before disconnecting the cables.

I have to think a lot of the jumping and electronic issues are just sloppy or incorrect hook up.
shorting the cables on the running car etc. Dropping one hot side to ground etc.

 

[bioburner]

With a better jump pack one sees if they have a connection. No large voltage spike when one turns the pack on and if the vehicle that's dead may not infect the donor but just screw the pack. BAd cell, bad cables and several other maladies.
I just seen cable set 4 gauge copper, 20ft for $20 at Walmart

 

[Uregina09]

Garak, are you referring to Bill Gardiner?

 

[901Memphis]

20 feet of 4/0 awg copper welding wire and some 600 amp parrot clamps should get the job done. Maybe 15 feet would be better

 

[3800Series]

Originally Posted By: bioburner
With a better jump pack one sees if they have a connection. No large voltage spike when one turns the pack on and if the vehicle that's dead may not infect the donor but just screw the pack. BAd cell, bad cables and several other maladies.
I just seen cable set 4 gauge copper, 20ft for $20 at Walmart


That is a good price in all honesty rather surprised. I bought a 16 foot set of 4 gauge copper cables for $49 a few years back so I'm fairly surprised but who knows what quality they are.

 

[Garak]

Originally Posted By: Uregina09
Garak, are you referring to Bill Gardiner?

I believe it was Brian Turner from the Canoe site's automotive section, though I've seen it spouted in other Canadian media. There's nothing quite like flagrantly trying to protect one's trade, without any regard for what happens in the real world. The panic I've read in some of these columns about doing boosts, changing oil, working on brakes, and so forth is just bizarre.

 

[mjoekingz28]

Originally Posted By: 901Memphis
20 feet of 4/0 awg copper welding wire and some 600 amp parrot clamps should get the job done. Maybe 15 feet would be better




You jumping big rigs?




I'm reading this (4/0) as 0000 btw. I was not even aware of this size. The charts I view, IIRC, go to 00 or 000 alt.

 

[bioburner]

I was as surprised. Pulled them out to check the cable and its fine strand but the clamps not top of the line but the average Joe doesn't need something strong enough to tow a car. Don't know how stiff the cables will be if it sees a MN winter.

 

[JHZR2]

Originally Posted By: 901Memphis
20 feet of 4/0 awg copper welding wire and some 600 amp parrot clamps should get the job done. Maybe 15 feet would be better



Im thinking more like 12' of 1/0, but generally agree...

 

[JHZR2]

Originally Posted By: 3800Series
Originally Posted By: bioburner
With a better jump pack one sees if they have a connection. No large voltage spike when one turns the pack on and if the vehicle that's dead may not infect the donor but just screw the pack. BAd cell, bad cables and several other maladies.
I just seen cable set 4 gauge copper, 20ft for $20 at Walmart


That is a good price in all honesty rather surprised. I bought a 16 foot set of 4 gauge copper cables for $49 a few years back so I'm fairly surprised but who knows what quality they are.


Theyre likely Aluminum wire coated with copper, and with copper coated steel clamps. Quality cables cost $$.

 

[JHZR2]

Originally Posted By: Garak
Originally Posted By: Uregina09
Garak, are you referring to Bill Gardiner?

I believe it was Brian Turner from the Canoe site's automotive section, though I've seen it spouted in other Canadian media. There's nothing quite like flagrantly trying to protect one's trade, without any regard for what happens in the real world. The panic I've read in some of these columns about doing boosts, changing oil, working on brakes, and so forth is just bizarre.


Some examples:

http://www.autoblog.com/2010/03/31/at-witz-end-throw-away-those-old-jumper-cables/

Quote:
"I would consider the warning to be quite strong," Goss explained. "Back before computers and sophisticated electronics on cars, there wasn't much of an issue other than folks getting hurt from exploding batteries. Today is a very different world, and there are thousands, if not millions, of cars damaged by old fashioned cables every year."

Here is why: You hook up the old-style cables properly and get the car with the dead battery started. At this point, there is one vehicle with a strong battery and one with a dead one, both running, so both alternators are working hard trying to charge the dead battery and replenish the energy drawn from the good one.

"As long as the cables are connected," Goss continued, "the two batteries act as buffers to contain maximum voltage rise. But as soon as the first cable end is removed, the systems go nuts. When the first cable is removed, the voltage reference is gone. It instantly changes from the level of two batteries and two alternators to one battery and one alternator.

"During this period of adjustment, the voltage regulator allows the alternator to climb to a very high voltage level. The alternators of both cars are unregulated for a few milliseconds, and during that brief time, the alternator can produce several hundred volts of low-amperage electricity. This high-voltage spike shoots through the electrical systems of both cars."

The effect is like a voltage surge running through a computer. It rarely destroys anything instantly but can weaken components of both vehicles, including engine control computers, alternators, sound systems or any of the dozens of electronic modules in modern cars, and there are usually no immediate symptoms because these parts are merely weakened.



http://www.mynrma.com.au/get-involved/advocacy/news/why-you-shouldnt-jumpstart-a-modern-car.htm

Quote:
The trusty jumper leads that a handy motorist would once have kept in the boot in case of a flat battery have become taboo for modern cars, and NRMA technical trainer Darrin Tucker says that’s with good reason.

“The big change from then to now is computers and it’s not as if a modern car has just one – a Mercedes-Benz S-Class from a few years ago has 64 ECUs (Electronic Control Units),” he said.

“Jaguar warned us that you could damage the whole wiring harness if you try to jump-start one of their cars, and quite frankly that warning is probably applicable to most vehicles built within the past five years.

“A five-year-old Audi was recently taken to an NRMA Approved Repairer with an electrical system so badly damaged by an attempted jumpstart that, in the end, it was actually cheaper to write the car off rather than repairing the damage.”

But what has driven this destructive change?

The simplest answer is … computers.



The one I find most dubious is the first one I quoted...

Quote:
"As long as the cables are connected," Goss continued, "the two batteries act as buffers to contain maximum voltage rise. But as soon as the first cable end is removed, the systems go nuts. When the first cable is removed, the voltage reference is gone. It instantly changes from the level of two batteries and two alternators to one battery and one alternator.

"During this period of adjustment, the voltage regulator allows the alternator to climb to a very high voltage level. The alternators of both cars are unregulated for a few milliseconds, and during that brief time, the alternator can produce several hundred volts of low-amperage electricity. This high-voltage spike shoots through the electrical systems of both cars."


IMO, this is an inductive spike, due to the removal of cables. Say 100A is flowing on a heavy gauge cable from a good source to one with really low voltage, so the voltage delta supports it. Pull that cable over a fraction of a second, and the change could be hundreds of Amperes over a hundredth (thousandth?) of a second or less so say 100/0.001 (for di/dt). Im not sure it gets us to the claimed hundreds of volts that could be observed. Personally observed testing with really high power batteries shows that 3x nominal voltage or so is viable... Im just not seeing how an alternator voltage regulator could go so out of control that it naturally putting out 100's of volts is viable.

 

[fdcg27]

Originally Posted By: Leo99
I don't futz around with older marginal batteries. Once they get marginal, they get replaced.

I'm going to buy a li ion jumper when I see one on sale.


Problem is that batteries can fail with little or no warning.
I've had a battery go from cranking the engine over just fine in the morning to having to push-start the car that afternoon, and a replacement battery made everything well again, so it wasn't as though anything else was wrong with the electrical system.
A jump pack is a waste to me, since you'll rarely if ever have any need for it, just as I've had cars go through their entire lives never needing a jump start and never having the spare tire on the ground.