Jumper cables

[mikefxu]

My edit time expired....

The only time I have had problems with jumper cables is when people try to start as soon as they are connected. I try to get at least 3-5 minutes of 1/4-1/3 of max rpm from the vehicle providing the jump.

Since the Prius should not provide a jump I got a lithium jump starter pack for it. I still carry a set of jumper cables if I need to be jumped. I guess the cables are redundant due to the pack but I already had a set of cables so I keep them in there.

 

[JHZR2]

Originally Posted By: mikefxu

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



From Amazon:

Quote:
These cables were recommended as they were made with 100% copper wire (perhaps this was true preciously). I emailed the company and got confirmation before purchasing. After receiving the cables, I immediately initiated a return after taking pictures of the conductors. I then emailed the company with the pictures - to which I got a reply telling that they gave me incorrect information and the wire runs consists of 70% copper and 30% aluminum. Looking at the pictures and examining the cables ends themselves, I wouldn't believe them if they told me it was 30% copper and 70% aluminum. Every single wire strand looks to be copper plated aluminum, not a single solid copper wire can be seen (I took pictures with my 1:1 macro lens). I know that there is no mention of the material of the wires themselves in the description, but I've purchased based on the reply I got from the company. I might have kept it if it was indeed 70% copper, but there is no way that is true. So if you are expecting a 100% copper cable set, this is not it. The cables also have different packaging, and now doesn't include the storage bag and wire brush as the Amazon description mentions. I am very disappointed at the reponse from the company, as if they are trying mislead those who doesn't know better. If they stand by their now 70% copper statement, then it should be a piece of cake for them to outline and identify the copper wires from the pictures I've sent them, that is, if copper is silver in color. I would have been eager to write a great review if the product was indeed what they claimed. I'm sure the cables will work, but so would other cheaper same gauge copper plated aluminum cables.



Im in the same boat - jumping smaller 4 cyl engines, maybe a v6. Even if Im jumping a diesel, I know that the starter on my OM617 engines is rated at 1.7kW.

So theyre working fine, even though some Cu/Al mix.

I think the value proposition for seldom if ever used cables is indeed CCA. If I had a flaky vehicle or tended to use them a lot, then the Cu cables is the only choice. Ditto if I was starting large diesels or something in very cold weather.

 

[Mamala Bay]

From my expereince if the jumper cables are used frequently especially on commercial heavy duty batteries the cables will degrade from heat. A good quality 2 gauge and you pay for it will last for years. BUT this for heavy commercial usage. I've seen even high priced quality 2 gauge jumper cables take beatings you can see and feel it degrades..it doesn't take heat like when new...the cables get pretty hot to the touch

Depending on your usage I would pay for what is necessary...but if you want over value that is up to you. Over used jumper cables can be a safety issue.

 

[Trav]

How about surplus cable and clamps like these..

http://www.tooltopia.com/k-tool-internat...CFQhk7AodW2MAUw

http://www.skycraftsurplus.com/weldingwire.aspx

http://www.skycraftsurplus.com/weldingcable2awg.aspx

 

[Shannow]

Originally Posted By: JHZR2
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.


You know your stuff JHZR2...

 

[JHZR2]

Originally Posted By: mikefxu
My edit time expired....

The only time I have had problems with jumper cables is when people try to start as soon as they are connected. I try to get at least 3-5 minutes of 1/4-1/3 of max rpm from the vehicle providing the jump.

Since the Prius should not provide a jump I got a lithium jump starter pack for it. I still carry a set of jumper cables if I need to be jumped. I guess the cables are redundant due to the pack but I already had a set of cables so I keep them in there.


The prius cannot be used as a jump vehicle? I wonder why.

 

[JHZR2]

Originally Posted By: Mamala Bay
From my expereince if the jumper cables are used frequently especially on commercial heavy duty batteries the cables will degrade from heat. A good quality 2 gauge and you pay for it will last for years. BUT this for heavy commercial usage. I've seen even high priced quality 2 gauge jumper cables take beatings you can see and feel it degrades..it doesn't take heat like when new...the cables get pretty hot to the touch

Depending on your usage I would pay for what is necessary...but if you want over value that is up to you. Over used jumper cables can be a safety issue.


This makes total sense.

The flip side of this is what I was really after - from a materials standpoint, my understanding is that even high Cu content Al alloys dont flex and bend too well. Doesnt much matter for say, a 200A service to your home, or the feeder to s subpanel, where ampacity is rated at 60 degrees (i.e. very much derated from insulation degradation temperatures, etc), and where there is never much movement...

But jumper cables are meant to be unrolled and re-rolled. Connections will get hot. Test a battery with a 400A discharge via carbon pile tester and it will be plain to see.

But the number of times that CCA can be unrolled, used, re-rolled, while I suspect to be lower than Cu, is the real question.

Of course heavier gauge CCA may stay cooler than lighter gauge Cu, and if that is the case, the degradation may actually be lower.

For real use Cu is the ONLY way to go... But for a convenience item in a kit that may never be used, a decently rated CCA wire may be just fine... Thats all Ive been trying to get at...

 

[EdwardC]

I think that part of the issue with CCA wiring comes from vendors claiming a certain wire gauge, but selling a product that has the same or smaller cross sectional area, at least, I've seen a lot of that when looking at car audio wiring kits.

I completely agree that as long as the voltage drop is maintained, considering the wire resistance, it shouldn't matter a lick if the wire is aluminum or copper.

The jump box I keep is a Lithium Iron Phosphate (4S) based pack, a safer lithium based chemistry, yet has very high discharge rates.

 

[JHZR2]

Originally Posted By: EdwardC

The jump box I keep is a Lithium Iron Phosphate (4S) based pack, a safer lithium based chemistry, yet has very high discharge rates.


We have done a lot of testing on LFP. It will still outgas flammable electrolyte and burn. An LFP 26650 has an AC 1kHz impedance of around 8mOhm, and DC impedance is about double that so you can do the math. Still can provide a lot of juice...

 

[JHZR2]

For anyone interested, this is about the best table Ive seen that depicts the resistivity of Cu vs Al for solid and stranded wires.

http://www.okonite.com/engineering/dc-resistance.html

With this, one can easily see the size wiring they need if going for Cu vs Al. Of course, practically speaking, if you buy CCA, the real decision only is whatever the biggest gauge you can find.

Question is if one can find one heavier than 6 or 4 ga. Again, thats where conductor flexibility comes in...

 

[another Todd]

It's just like any other tool. If you use it to make a living you buy the best, or at least very good quality. If you don't make a living with it and only will use it occasionally, then you might buy a lessor quality, it will still work, it just might have limitations which you should understand going into the purchase.

 

[HTSS_TR]

Agree.

I needed/used jumper cables once or twice in the last 15-20 years for 3-4 cars, so it was like 1 use every 40-50 car years. I bought low cost 50A alligator clamps and utilized discarded 10 gauge speaker wire(double wire per cable) to make cheap jumper cables. My home made cables are about 6-7 gauge and the cost was $3-4 and it worked for not so deep discharged battery.

I now have jumper cables in each car trunk, you never when/if you need it and $3/4 per pair is cheap enough to have/make 4-5 pairs.

 

[EdwardC]

Originally Posted By: JHZR2
Originally Posted By: EdwardC

The jump box I keep is a Lithium Iron Phosphate (4S) based pack, a safer lithium based chemistry, yet has very high discharge rates.


We have done a lot of testing on LFP. It will still outgas flammable electrolyte and burn. An LFP 26650 has an AC 1kHz impedance of around 8mOhm, and DC impedance is about double that so you can do the math. Still can provide a lot of juice...


Very interesting! LFP is supposedly much safer than other Lithium chemistries, at least according to the internet. Is that still accurate in your experience? How do they compare? I'm mostly concerned since I'm carrying around the LFP jump box in the car all over.

Sorry hijacking the jumper cable thread..

 

[JHZR2]

Originally Posted By: EdwardC
Originally Posted By: JHZR2
Originally Posted By: EdwardC

The jump box I keep is a Lithium Iron Phosphate (4S) based pack, a safer lithium based chemistry, yet has very high discharge rates.


We have done a lot of testing on LFP. It will still outgas flammable electrolyte and burn. An LFP 26650 has an AC 1kHz impedance of around 8mOhm, and DC impedance is about double that so you can do the math. Still can provide a lot of juice...


Very interesting! LFP is supposedly much safer than other Lithium chemistries, at least according to the internet. Is that still accurate in your experience? How do they compare? I'm mostly concerned since I'm carrying around the LFP jump box in the car all over.

Sorry hijacking the jumper cable thread..


Happy to discuss. LFP does not have the same exothermic reaction under abusive and faiure conditions as typical metal oxide cathodes used in other Li-ion cells. That said, it doesnt mean that the cells are safe. The electrolyte in Li-ion cells can still vent at a few hundred psi, and in the presence of an ignition source (the electrolytes are conductive in the fas phase, so its assured) will burn in a typical organic fire, and this can easily produce propagation.

If one looks at cell impedance, it can be observed that the jumping amp rate is nearly shirt-circuit current level, and shorting Li-ion cells most often causes a flaming vent, regardless of chemistry. Further, Li-polymer cells will have worse impedance due to poorer conductivity and worse interfacial resistance, and thus will get hotter and have a more abusive condition to them.

Interestingly, looking on amazon, it appears that all these systems either have some kind of a timer-controlled MOSFET or have strict requirements to only leave the unit connected for 10 seconds or less.

These things are an interesting concept, and I have an external battery for my e-gadgets. But for operations at these discharge rates, and to sit in a trunk where the temperature can get dangerously close to the SEI-layer decomposition temperature, well, no thanks...