Good gauge for Jumper cables?

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Looking to buy a set of jumper cables (maybe in an emergency kit) for my car. What is a good gauge? most of the ones I see are 10 gauge, and a few are 8 gauge.
 
Get the heaviest ones you can afford. And the longest, so that you can park behind the other vehicle. Much safer if you are on the side of the highway. If you have an industrial supply store nearby, check out the price of bulk #4 welding cable. Get as much as you can afford and some 400 Amp clamps from an auto parts store and you will have a set of jumpers better than any commercially available ones, probably for less cost. You could jump start an 18 wheeler with them. 10 Ga are good for jump starting lawn tractors.
 
Mine are made from electric welding cable. Very heavy clamps with a separate wire for each side, and jumper wire connecting each side of each clamp. Also extra ground wire also made of welding cable comes off of each negative lead and goes to a mid size clamp for an extra ground connection for each side of each ground. Also each large clamp has a Alligator clamp fed by multiple runs of stranded 12GA that provides an additional connection to the bolt for side terminals of the battery. Each cable is wound up and both then place in a clear plastic bag, that is kept in a large canvas bag. My cost $80 for cable and 40 for the 4 large clamps, plus the smaller extra ground clamps, plus the 4 extra alligator clamps. All connections are soldered, and also the fine stranded welding cable is protected from battery acid exposure by multiple applications of clear wood varnish.

Made this up years ago and never had a vehicle that I could not get started with it.

You do have to run the good vehicle for ten minutes to charge a dead battery before trying to start the dead vehicle.

I always get all the available keys to the dead vehicle in my possession before connecting my vehicle to the dead vehicle. The regulator for the alternator in you vehicle only senses the system voltage and does not sense how much current the alternator is putting out. If someone cranks a vehicle while your engine is running your alternator will put out too much current and damage the output diodes. NEVER let anyone talk you into allowing them to crank their vehicle while you engine is running. Always have he engine of the good vehicle off when jump starting any vehicle. If someone tells you that it will work better if you run you engine when they try to start their vehicle, tell them yes but it will damage you alternator. If they get insistent ask them to give you $150 to hold for two week so you can replace you alternator if the diodes get damaged. Usually when these diodes get damaged they go leaky, and this will put a small constant drain on you battery that will only be noticeable if you let your vehicle sit unused for two or more days. Then it will completely drain you battery and you vehicle will not start. Because it requires you to let your vehicle sit for two or more days it might not show up for weeks if you normally use your vehicle every day.

NEVER let anyone talk you into allowing them to crank their vehicle while you engine is running. That is why I hold the keys to the bad vehicle, so there is no way they can do that to my alternator.

By a separate wire for each side I mean to say that the negative actually has two welding cable wires running from the one vehicle to the other, and the positive actually has two welding cable wires running from the one vehicle to the other.
 
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How is this for a make shift jumper cable set up?

Years ago, back when vehicles all had metal bumpers, and top post batteries, I had to get a vehicle with a bad battery to start. No one had jumper cables.

I slowly moved my vehicle with someone telling me how far apart they were. We touched the bumpers together front to front (that was the negative connection) and aligned so the batteries were close. Then I took the L shaped tire irons form both vehicles and held them so the small part of each L was touching a positive post. The end of the long part of each L reached and over lapped each other by a little more than one inch. I held those tight against each other (that was the positive connection). Told the owner of the bad vehicle to try it and it fired right up.

Hows that for McGivering a jump start?

To bad you can't do it with plastic bumpers and side terminals today.
 
I had a $150 gift certificate and spent it on a set of 25' 2-gauge cables with 500 amp clamps... wasted money. I think your Cavalier would be happy with 4- or even 8-gauge conductors and never come close to heating them up unless you allow a trucker to cop a jump from you.

Look for sturdy, mean clamps. Rubbery rather than hard plasticky insulation tends to be more flexible in extreme cold and coils up more tightly/easily for storage. 20' should be plenty long enough to safely jump cars that are parked head to toe. My old 16' cables were never too short, actually.

You can get a set of decent 20' 4-gauge cables from Amazon for less than $50. If you're feeling frugal, hit Wal-Mart and get a set of 8-gauge jumpers for much less. No worries if you're using the cables to jump your own car, but you shouldn't be offering jumps to industrial engines with them.
 
Originally Posted By: JimPghPA
I always get all the available keys to the dead vehicle in my possession before connecting my vehicle to the dead vehicle. The regulator for the alternator in you vehicle only senses the system voltage and does not sense how much current the alternator is putting out. If someone cranks a vehicle while your engine is running your alternator will put out too much current and damage the output diodes. NEVER let anyone talk you into allowing them to crank their vehicle while you engine is running. Always have he engine of the good vehicle off when jump starting any vehicle. If someone tells you that it will work better if you run you engine when they try to start their vehicle, tell them yes but it will damage you alternator. If they get insistent ask them to give you $150 to hold for two week so you can replace you alternator if the diodes get damaged. Usually when these diodes get damaged they go leaky, and this will put a small constant drain on you battery that will only be noticeable if you let your vehicle sit unused for two or more days. Then it will completely drain you battery and you vehicle will not start. Because it requires you to let your vehicle sit for two or more days it might not show up for weeks if you normally use your vehicle every day.

NEVER let anyone talk you into allowing them to crank their vehicle while you engine is running. That is why I hold the keys to the bad vehicle, so there is no way they can do that to my alternator.


Congratulations on a very well-made set of booster cables!

I occasionally jump trucks at work with my own vehicle, the Sierra, and have no hesitation starting the truck up with the Sierra engine running. I don't think there is an issue here for the following reasons.
1) The Sierra system voltage might drop,at the most, to 10v when the truck engine is being cranked. There is only so much current that the jumper cables will allow and the Sierra battery is a huge electrical "reservoir".
2)10v vs 14v is a factor of only 1.4. The Sierra is only idling
and the idle current it generates at 10v will still be less than its maximum rated current at around 13v(145 amps, BTW), running at speed.
3) This higher current while the truck engine is being cranked only lasts for 10 to 15 secs, it is not as if you are subjecting the alternator to high currents for hours at a time.
 
I bought a nice set of 6 gauge, 16 ft. cables from Advance Auto for $24.00 about two weeks ago. I believe they will serve me well for general automotive use.
 
You don't need to go crazy with super heavy cables. Johnny has the right idea in my opinion. Now if your looking for cables to start a big Diesel in an 18 wheeler then we're talking 2 or 4 gauge wire.
 
I like the sound of the 6 auge and 16' too. the longer the cables, the heavier they need to be. Not sure what mine are, but they are welding cable based.
 
Originally Posted By: Johnny
I bought a nice set of 6 gauge, 16 ft. cables from Advance Auto for $24.00 about two weeks ago. I believe they will serve me well for general automotive use.


+1 get these. You will be fine.
 
I have 2 sets of 20' jumpers made from used #4 superflex welder cable. I got the cable from a large welding shop nearby that replaces it's cables as a PM procedure. If the welder has 100' of cable on his machine, usually the "inside" 50' is not used nearly as often and if you can get a chunk of that it would make a great jumper cable ( or two ).
The welding cable stays very flexible in winter and is the best IMHO.
 
Assuming the recipient vehicle has a half decent battery, even if discharged, you can trade off cable thickness against time spent boosting. If you let the donor vehicle engine run for 10 mins and put some charge into the recipient vehicle battery then 8ga cables will give as strong a boost as 4ga cables would if the donor engine is not run for ten minutes.

Depending on how often you anticipate boosting, the trade-off might be worthwhile. You may not want heavy bulky cables taking up space in your car. I keep a set of 10ga cables in my truck, the cables are very compact and slide under the passenger seat.
 
The wire gauge doesn't matter. That isn't what starts the car. Good clamps are what you want. What I do is solder wire between the two clamp halves around the hinge. This almost doubles the amount of power that can be delivered before being disconnected by a spark fault. This lets the cheap cables deliver the same performance as the expensive ones.

Originally Posted By: JimPghPA

The regulator for the alternator in you vehicle only senses the system voltage and does not sense how much current the alternator is putting out. If someone cranks a vehicle while your engine is running your alternator will put out too much current and damage the output diodes.

Alternators are current limited so can run any size load without damage. I always start cars with the other engine running and the alternators are never damaged.

Most of what the jumper cable does is charge the dead battery. A little surface charge in the dead battery will kick out most of the power leaving little need for large wire or heavy current from the donor alternator.
 
making a custom set sounds great, but how often are you guys actually jumping cars? I got a nice set back in '95, I think I've used them 3-4 times since then. most times I had to go looking for them; I think I only needed them for myself once.
a basic store set should be fine, solder the cable crimp if you like.
 
GEORGE7041, and severach,

GEORGE you wrote:

I occasionally jump trucks at work with my own vehicle, the Sierra, and have no hesitation starting the truck up with the Sierra engine running. I don't think there is an issue here for the following reasons.
1) The Sierra system voltage might drop,at the most, to 10v when the truck engine is being cranked. There is only so much current that the jumper cables will allow and the Sierra battery is a huge electrical "reservoir".
2)10v vs 14v is a factor of only 1.4. The Sierra is only idling
and the idle current it generates at 10v will still be less than its maximum rated current at around 13v(145 amps, BTW), running at speed.
3) This higher current while the truck engine is being cranked only lasts for 10 to 15 secs, it is not as if you are subjecting the alternator to high currents for hours at a time.

Regarding your:

2)10v vs 14v is a factor of only 1.4. The Sierra is only idling
and the idle current it generates at 10v will still be less than its maximum rated current at around 13v(145 amps, BTW), running at speed.

The voltage regulator that drive the alternator only senses the system voltage and the ambient temperature. It uses the ambient temperature to determine the voltage the battery should be charged up to. If the output is loaded so it falls below the desired voltage the regulator will drive to the best of its ability. This drive current is limited by the internal resistance of the armature of you alternator. If the RPM of the alternator is high enough the alternator will put out enough current to bring the system voltage back up to the desired voltage. When the system voltage reaches the desired voltage the regulator regulates the drive to the alternator armature to keep the system voltage at that voltage. The system voltage does not have to fall off by much for the regulator to drive the armature of the alternator as hard as it can to bring it back up. Because the regulator is solid state a drop off of only a few mill volts (a few 1/1000 of a volt) will cause the regulator to drive the alternator as hard as it has to to bring the voltage back up. Now if the RPM's are not high enough, then the alternator can not produce enough power and will not bring the system back up.

However, a starter motor can draw the maximum power from a battery when the resistance of the starter = the internal resistance of the battery. At that time the battery output Voltage drops to 1/2 of the non loaded voltage. Normally when you crank you engine on a very cold day the engine is not cranking fast enough to allow the alternator to produce enough current to damage the out-put diodes.

Now if the good vehicles engine is running the alternator is turning much faster than when the engine is slow cranking during a hard start. If the bad vehicle is a hard start the battery of the good vehicle can be pulled low enough to allow the alternator of the good vehicle to put out too much current. The output windings of a alternator are three phase Delta winding connected to a 6 diode full wave three phase bridge rectifier.

Regarding your:

3) This higher current while the truck engine is being cranked only lasts for 10 to 15 secs, it is not as if you are subjecting the alternator to high currents for hours at a time.

These diodes are solid state and it only takes a fraction of a second of putting too much current through them to permanently damage them. They usually go leaky and allow a reverse flow through the winding that will act as a constant drain on the battery. I have seen this several times and it is always after someone has jumped started a bad vehicle with the good vehicle engine running. Ask any good alternator repair shop.


To severach, You wrote:

Alternators are current limited so can run any size load without damage. I always start cars with the other engine running and the alternators are never damaged.

There is NO current limit, and there is NO current sensing on the alternator. Some high end units like those in a Corvette have a temperature limit, but NO current limit.

I have a degree in electronics, and have looked at the schematics of how these linear regulators are designed. I understand them down to each component, and what each component does and how it interacts with the entire regulator. I have designed similar regulators for cars, and motorcycles.

If you run the good vehicle while you are cranking the bad vehicles engine you are rolling the dice about damaging the alternator of the good vehicle. The only thing that limits the output current is how poor the connections are, and how high you idle is, and how low the cranking vehicle pulls the battery on the good vehicle. If the bad vehicle pulls enough current the good vehicle battery will drop low enough to allow the alternator to put out enough current to damage the output diodes if the RPM's are high enough.
 
I always rev the donor car, both to get to the rated alt output at 3k RPM or so and also on the theory that it shares the load across all the alt diodes. Never had a problem. I even had my wife (in my car
mad.gif
) & coworker hook up cables backwards on a honda, blew the honda main fuse and my alt made it through unscathed 5 years ago. My rule is "motors off when hooking up" (keeps the voltage difference down, less sparking & arcing) then start the donor and leave it running.

There are kits to make DC welders out of old alts and they seem to survive that!

My jumper cables are 10 gauge big lots cheapies. They've started plenty of other cars. Modern gear reduction starters don't draw the current of older straight drive ones. They just turn REALLY SLOWLY when current-limited, yet inertia gets the engine up to speed and it catches.
 
The answer is, as usual, "depends". Cranking current for an gas engine is about 1 amp per cubic inch displacement (a friend and I have actually verified that this is correct using a current probe). If you have a 500 cu. in. 70's caddy, you are going to need 2 ga. or better. A 2 liter import is going to be plenty happy with 8 ga.

If anyone knows what the current cranking requirements for a diesel are, I'd like to know. Since most of them use gear reduction starters, it might be the same or close.
 
JimPghPA, you've just about covered almost all bases. I too have a good background in electronics, and have done a little custom electronic design work in the past. Solid state equipment is quite delicate and a few milliseconds of operating these devices above their electrical ratings can toast them permanently. If the other guys have not experienced any damage to their charging system while running the engine and crank-assisting another vehicle, I'd say they are very lucky indeed.

Merely connecting the jumper cables with the alternator energized can generate nasty sparks and electrical transients that solid state diodes don't take a fancy to. Assisting another vehicle with a weak battery while your engine is also running places a triple whammy on your own alternator, especially if your own battery is not in tip top condition. Your alternator will have to 1) charge your own battery especially if you've just restarted your vehicle, 2) try and charge the other car's weak battery, and 3) supply starting current to that car's starter, which typically draws 150 to 200 amperes or so. Sure, my and the other car's batteries will supply some of those 200 amperes, but if it were my vehicle, I'd want my engine to be off.
 
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