Jumper cables

[JHZR2]

Ok, some folks seem to need to review current and conductor ampacity.

It's pretty simple - the conductance of aluminum is somewhat poorer than copper, so one needs a slightly larger Aluminum conductor.

Once you have that heavier conductor, the voltagd drop for the same length wire is the same.

So, for example, for a few hundred amps, the voltage drop (which is what it's all about) might be the same with 4 ga copper and 2 ga aluminum. Remember, the only term of relevance is voltage drop, which can be calculated as current*resistance. Aluminum has a higher resistance for a given gauge, so the drop is higher. But that is easily mitigated with a bigger conductor. And since the density of Aluminum is like 1/4 that of Cu, the mass required for equal voltage drop is miniscule.

So my curiosity was more about mechanical longevity of CCA. The current carrying capability of Al vs Cu and how to engineer around it is well known.

Of course for the same price, and/or where the value lies, if Cu is a better value, great, but Al is still half or less than Cu on a conductor cost basis.

 

[901Memphis]

Why not just grab a Noco genius boost? Then you don't need another car to start your self. I tested one and it was able to start my Taurus with no battery at all.

 

[JHZR2]

No desire to have the added cost and replacement issues with batteries. No booster pack for me. If I was to do that, I'd just buy a group 49 battery and keep it in a float charger.

 

[Clevy]

Originally Posted By: Charlie1935
I made a set with 00 welding cable 20' long 45 years ago and they still work great.
A little heavy though.



I found some welding cables onsite about 15 years ago and turned them into jumper cables. 20' long and will get my forklift going.
By far the best cables I've ever had and they aren't even real cables.


Anyways my mom got this thing bit plugs into your cigarette lighter or power point in your vehicle. It charges the battery via that point. I think they are 20' long and go from the running vehicles power point to the dead cars booster point.
I think they are pretty slick. No standing outside freezing.
If I was going to be buying any this would be what I'd look at first.

 

[JHZR2]

Originally Posted By: Clevy
Originally Posted By: Charlie1935
I made a set with 00 welding cable 20' long 45 years ago and they still work great.
A little heavy though.



I found some welding cables onsite about 15 years ago and turned them into jumper cables. 20' long and will get my forklift going.
By far the best cables I've ever had and they aren't even real cables.


Anyways my mom got this thing bit plugs into your cigarette lighter or power point in your vehicle. It charges the battery via that point. I think they are 20' long and go from the running vehicles power point to the dead cars booster point.
I think they are pretty slick. No standing outside freezing.
If I was going to be buying any this would be what I'd look at first.


Thing with those chargers is that most cig ports are only good for 5-20A, so these packs aren't actually jumping the car.

And a 3Ah LI-ion cell set just doesn't have the energy. If they're goingvto do the 200-400A they claim, that's upwards of 100 c-rate, which is abusive on those cells. So I suspsct there is some capacitor in there and that the pulse width is pretty poor.

If they get the job done, great, but I'm not interested in being on a replacement path for a battery that has finite calendar life when I rarely if ever need/use cables anyway.

 

[spasm3]

If you make a set with the welding cables, do you wrap the wires together? Wrap them with electrical tape, or just leave them single?

 

[Merkava_4]

Originally Posted By: EdwardC
That set Merkava linked looks like a great price for real copper wires, might be on the shorter side, but workable. I haven't really seen a set of solid copper jumpers for less than that.


That's true, but JHZR2 never considers my recommendation; nor does he ever say why he doesn't like the recommendation.

 

[JHZR2]

Originally Posted By: Merkava_4
Originally Posted By: EdwardC
That set Merkava linked looks like a great price for real copper wires, might be on the shorter side, but workable. I haven't really seen a set of solid copper jumpers for less than that.


That's true, but JHZR2 never considers my recommendation; nor does he ever say why he doesn't like the recommendation.

Not true!! I was looking for heavy gauge cables at Amazon and they were priced in the hundreds (!) of dollars. The ones you showed are perfect in terms of price, though many recommend 16-20ft instead (doesn't concern me as much).

Sone tend to overstate starting current requirements. I'm not starting a car in the arctic. Something that heavy for a compact "in a pinch" set may be overkill, since I already have a set of very heavy, quality ones.

But thanks! Excellent recommendation and find!

 

[Fordtrucktexan]

Seconded on welding cables!

A friend of mine was given an old rusted out welding machine that had kicked the bucket a long time ago. He made a wet of jumper cables from the leads. They're thicker than 0 gauge and about as heavy as a car battery.

 

[901Memphis]

My noco has a 24Wh pack and was able to start my Taurus and after starting my Taurus six times with no battery it indicated full state of charge (75-100% at least)

I think it's much easier than carrying cables or a spare battery and I've proven it's got every bit of its rated amperage. If you're curious about the internals I opened it up.

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3523151/Noco_Genius_Boost_Exposed!!!

 

[Oil Changer]

Every couple feet with electrical tape will suffice.

Originally Posted By: spasm3
If you make a set with the welding cables, do you wrap the wires together? Wrap them with electrical tape, or just leave them single?

 

[Oil Changer]

What the heck was this post all about? No one above this post said anything inaccurate. In any given gauge, the copper is always better. Your title should read, "Best Cheap Jumper Cables". Get the aluminum. They will work well coiled up in the original package in the darkest corner of your trunk. Pretty simple.

Originally Posted By: JHZR2
Ok, some folks seem to need to review current and conductor ampacity.

It's pretty simple - the conductance of aluminum is somewhat poorer than copper, so one needs a slightly larger Aluminum conductor.

Once you have that heavier conductor, the voltagd drop for the same length wire is the same.

So, for example, for a few hundred amps, the voltage drop (which is what it's all about) might be the same with 4 ga copper and 2 ga aluminum. Remember, the only term of relevance is voltage drop, which can be calculated as current*resistance. Aluminum has a higher resistance for a given gauge, so the drop is higher. But that is easily mitigated with a bigger conductor. And since the density of Aluminum is like 1/4 that of Cu, the mass required for equal voltage drop is miniscule.

So my curiosity was more about mechanical longevity of CCA. The current carrying capability of Al vs Cu and how to engineer around it is well known.

Of course for the same price, and/or where the value lies, if Cu is a better value, great, but Al is still half or less than Cu on a conductor cost basis.

 

[Shannow]

^+1

Do the jumper and the jumpee battery impedances have to match in the cost benefit equation ?

 

[JHZR2]

Originally Posted By: Oil Changer
What the heck was this post all about? No one above this post said anything inaccurate. In any given gauge, the copper is always better. Your title should read, "Best Cheap Jumper Cables". Get the aluminum. They will work well coiled up in the original package in the darkest corner of your trunk. Pretty simple.

Originally Posted By: JHZR2
Ok, some folks seem to need to review current and conductor ampacity.

It's pretty simple - the conductance of aluminum is somewhat poorer than copper, so one needs a slightly larger Aluminum conductor.

Once you have that heavier conductor, the voltagd drop for the same length wire is the same.

So, for example, for a few hundred amps, the voltage drop (which is what it's all about) might be the same with 4 ga copper and 2 ga aluminum. Remember, the only term of relevance is voltage drop, which can be calculated as current*resistance. Aluminum has a higher resistance for a given gauge, so the drop is higher. But that is easily mitigated with a bigger conductor. And since the density of Aluminum is like 1/4 that of Cu, the mass required for equal voltage drop is miniscule.

So my curiosity was more about mechanical longevity of CCA. The current carrying capability of Al vs Cu and how to engineer around it is well known.

Of course for the same price, and/or where the value lies, if Cu is a better value, great, but Al is still half or less than Cu on a conductor cost basis.


No, there is a blind adherence to copper cables without a real understanding why. That's what is displayed post after post without any good technical basis to back it up.

News flash, a 2 ga CCA set will have the same voltage drop as a 4 Ga Cu set at half the cost and a third the mass.

Everybody knows that Cu conducts better, but it doesn't mean that CCA won't work.

Guess what, I'm not doing any jump starting in the Arctic.

For sonething with extremely seldom use and very infrequent unrolling, CCA may well present best value, if selected properly and depending upon where cost/size/value lies.

Not cheap, best value american made. Again, the only downside I've seen to CCA sized gauge wise for the appropriate equivalent voltage drop is that they may not have the bend life of Cu.

So since this is apparently too difficult for comprehension, I'll rephrase the question -

For the same conductor performance (voltage drop under load), what is the downside to CCA?

 

[JHZR2]

Originally Posted By: Shannow
^+1

Do the jumper and the jumpee battery impedances have to match in the cost benefit equation ?


I've run studies and efforts looking at slight impedance mismatches in parallel cells, and yes, the impedance mismatch can create substantial differences in terms of cell to cell loading.

A discharged Pb-acid battery will have a good deal higher impedance than the charged one, so will pass much less current. The abusive condition occurs if the lower one discharges enough to send a cell into reversal under load. That's precisely why a 24Wh boost pack on a 1000Wh lead acid battery is of little use. The power to energy ratio and depletion level and c-rate border on abusive, and the losses are so high that one can not get enough charge in to prevent a badly depleted cell from going into reversal.

When two cars are connected, the best bet is to allow the source car to help charge the depleted battery a bit before jumping. This allows some charge to be provided to the dead battery.

And to move double digit amps to the dead battery is something that even thin gauge CCA can do.

I've had shorted cells that heavy cables straight off a dual battery wrecker couldn't overcome. Some situations require escalation. But a once in a blue moon (last time I jumped a car was 2008) use set of cables in my local environment is another story, especially if I have aught Cu cables at home and are considering a small, light, road trip pack or something for the wife's car or a beater.

 

[another Todd]

Welding cable have all the good stuff; Very high fine wire count for high current capability and flexibility, rubber insulation for flexibility and durability. Vinyl coated or coarse wires are not as flexible and don't carry the high current. Size or gauge of the wire is only important if you will be in a hurry. 4 or even 6 ga. wires are fine if you can connect and wait a while before attempting to jump a low battery. This charges the dead battery. The lower the dead battery is the longer you have to wait. The heavier the wire the less you have to wait, as it is more able to send the full current required for starting through the cables, and you have less need to "pre-charge" the battery. I use 4 ga very fine wire cables, they are about 25 years old, 20 feet long and are perfect.

 

[901Memphis]

Originally Posted By: JHZR2
Originally Posted By: Shannow
^+1

Do the jumper and the jumpee battery impedances have to match in the cost benefit equation ?


I've run studies and efforts looking at slight impedance mismatches in parallel cells, and yes, the impedance mismatch can create substantial differences in terms of cell to cell loading.

A discharged Pb-acid battery will have a good deal higher impedance than the charged one, so will pass much less current. The abusive condition occurs if the lower one discharges enough to send a cell into reversal under load. That's precisely why a 24Wh boost pack on a 1000Wh lead acid battery is of little use. The power to energy ratio and depletion level and c-rate border on abusive, and the losses are so high that one can not get enough charge in to prevent a badly depleted cell from going into reversal.

When two cars are connected, the best bet is to allow the source car to help charge the depleted battery a bit before jumping. This allows some charge to be provided to the dead battery.

And to move double digit amps to the dead battery is something that even thin gauge CCA can do.

I've had shorted cells that heavy cables straight off a dual battery wrecker couldn't overcome. Some situations require escalation. But a once in a blue moon (last time I jumped a car was 2008) use set of cables in my local environment is another story, especially if I have aught Cu cables at home and are considering a small, light, road trip pack or something for the wife's car or a beater.



In most cases a car needing a jump isn't completely discharged, just discharged enough to not have enough amps to start it.

Either way I purposely drained my battery to 9.9v and the GB started my Taurus no problem and my charger didn't have any issues charging the battery after I took it inside. It's still working just fine and holding a great charge. Impressive considering how old it is and what it's been through. You could say I was trying to kill this Exide battery but it's a superstar. It's in the link also.

 

[JHZR2]

Originally Posted By: 901Memphis
Originally Posted By: JHZR2
Originally Posted By: Shannow
^+1

Do the jumper and the jumpee battery impedances have to match in the cost benefit equation ?


I've run studies and efforts looking at slight impedance mismatches in parallel cells, and yes, the impedance mismatch can create substantial differences in terms of cell to cell loading.

A discharged Pb-acid battery will have a good deal higher impedance than the charged one, so will pass much less current. The abusive condition occurs if the lower one discharges enough to send a cell into reversal under load. That's precisely why a 24Wh boost pack on a 1000Wh lead acid battery is of little use. The power to energy ratio and depletion level and c-rate border on abusive, and the losses are so high that one can not get enough charge in to prevent a badly depleted cell from going into reversal.

When two cars are connected, the best bet is to allow the source car to help charge the depleted battery a bit before jumping. This allows some charge to be provided to the dead battery.

And to move double digit amps to the dead battery is something that even thin gauge CCA can do.

I've had shorted cells that heavy cables straight off a dual battery wrecker couldn't overcome. Some situations require escalation. But a once in a blue moon (last time I jumped a car was 2008) use set of cables in my local environment is another story, especially if I have aught Cu cables at home and are considering a small, light, road trip pack or something for the wife's car or a beater.



In most cases a car needing a jump isn't completely discharged, just discharged enough to not have enough amps to start it.

Either way I purposely drained my battery to 9.9v and the GB started my Taurus no problem and my charger didn't have any issues charging the battery after I took it inside. It's still working just fine and holding a great charge. Impressive considering how old it is and what it's been through. You could say I was trying to kill this Exide battery but it's a superstar. It's in the link also.


200A under load (assume 24mOhm impedance of the battery pack, since a typical 26650 is around 8mOhm), which means 0.024Ohm x 200A = 4.8V DROP.


So the 11.1V pack (which may at full charge actually be as high as 4.1Vx3=12.3V) is around 6.3V under load.

This is very simple electrical engineering, and not sensible for starting unless there is a good boost converter and likelya decent electrochemical capacitor in there.

OR the cells are way derated, and actually much larger/lower impedance than nameplate shows.

Keep in mind also that 200A for say, five seconds of cranking is 200A * 5s = 200A-s * 1Ah/3600A-s = 0.28Ah * 11.1V = 3.1Wh. So notionally the thing should be suitable to discharge 5-6 times before thermal or undervoltage cut-outs occur. But thats assuming that there is zero discharge into the dead battery at the time. A starting battery for a car is somewhere around 0.006 Ohms. Using Ohm's law, one can easily calculate that 11.1V into 0.004 Ohm can priovide 2774A and 30kW. Of course the connected impedance and the battery impedance way limits that, but the connected battery looks for all intents and puroposes to be a short circuit.

So say the Noco is current-limited at 400A. After about 20s of being connected the 24Ah of the Noco would be depleted just from dumping into the depleted battery.

Cells can do this (Read the work of Chen from Saft and Wetz from University of TX) if you want to learn about realy low impedance loads and how cells can pulsed discharge in such conditions. However, such operations are typically only allowable under very shallow depths of discharge, and can be considered abusive if operated the wrong way. Abust of Li-ion can easily turn into a flaming release, particularly if cycled multiple times.

 

[JHZR2]

Originally Posted By: another Todd
Welding cable have all the good stuff; Very high fine wire count for high current capability and flexibility, rubber insulation for flexibility and durability. Vinyl coated or coarse wires are not as flexible and don't carry the high current. Size or gauge of the wire is only important if you will be in a hurry. 4 or even 6 ga. wires are fine if you can connect and wait a while before attempting to jump a low battery. This charges the dead battery. The lower the dead battery is the longer you have to wait. The heavier the wire the less you have to wait, as it is more able to send the full current required for starting through the cables, and you have less need to "pre-charge" the battery. I use 4 ga very fine wire cables, they are about 25 years old, 20 feet long and are perfect.


All good info. I agree with everything youve said, and the allowance of time to provide some charging is my typical operational scenario.

For those who just blindly poo-poo Al, they can see typical rating differences for Cu vs Al for terrestrial applications as a basis for the differences (rule of thumb is same, though DC conducting is different than AC).

http://www.allenelectric.com/referencedata/ampacity.htm

For continuous use ratings, an OK table is here:

http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm



On a related note, Delphi is moving this out...

Delphi Aluminum Cable Systems include a cost-effective, lightweight wiring alternative that offers up to 47 percent mass reduction compared to traditional copper core cable. Approximately one kilogram of aluminum can replace 2 kilograms of copper, providing equal conductivity.

http://www.delphi.com/manufacturers/cv/cables-wiring-cv/aluminum-cables

Here is some other reading for folks to do:

http://www.furukawa.co.jp/english/museum/floor3/03/23.htm


And again, Im not being a shill for CCA, and Cu is obviously a great standard choice for most anything... But it doesnt mean that CCA isnt necessarily a better choice for a once in a blue moon use, and that it has its place if the appropriate design for ampacity is selected (i.e. no loss leader 10 ga stiff aluminum conductor).

 

[mikefxu]

Advance Auto Parts almost always has 35% off and up to 50% off ($50 off $100). Last time we needed better quality (gauge) in a long length it made the cost much less. I have used the $50 off $100 to get a bunch of good quality oil filters (Bosch DP). We also use it about every 6 months to buy vehicle cleaning supplies for the company I work for. Also always use it for batteries, they are over $100 even for the small Honda's. I also use a cash back site, that is optional but I have notifications setup for both of them (fatwallet and slickdeals) so I know when Advance Auto Parts is doing $50 off $100.

http://www.fatwallet.com/Advance-Auto-Parts-coupons

I have mediocre cables for our vehicles since they were Hondas with small batteries. They have worked fine when I needed to jump other vehicles. They are nice that they ratchet shut, which has worked well with small side terminal bolts (GM). When I replace the batteries on our work trucks (GM) I make sure to get a battery with top and side terminals for easier jumping.

Set I have in each vehicle: http://www.amazon.com/Hopkins-BC0860-Performance-Ultimate-4-Gauge/dp/B002VHQ176

I have the 14' version that was on sale in 2011 and they have worked every time I have needed them.