Today the car wouldn't start at a friend's house who had no jumper cables. He had some electrical wire though. We were just starting to jury rig something when his wife showed up with cables in her trunk.
If we did jury rig electrical wires, we were unsure of what size would work.
How can we determine what size electrical wire would work to jump a typical sedan in an emergency?
There is no real way to do that and the quite minimal wire that some power bank starters is no real indication given that those are much shorter than normal jumper cables. And what works really depends on how f***ed the battery in the car that wont start is too. Sometimes the problem is just that the voltage with the battery in the car which wont start sags too much to provide enough voltage to see the spark plugs firing well and that the reason it doesn’t start. So you don’t necessarily need a lot of current thru the jumper to the car used to start it, its not actually turning the starter motor over.
Yep, someone gave my wife a pair of "ridiculously cheap"-looking jumper cables. And they worked when she needed them. In fact, looking back they have worked for us twice. But it took about 10 minutes of "revving" before the would turn over.
Sure there is moron, just apply Ohms Law and consult a wire gauge table. An even simpler way is to just look at some jumper cables and select a similar wire size. More problematic is how to connect that wire to the batteries, ie people typically don't have giant size alligator clamps or similar laying around.
and the quite minimal wire that some
He said jumper cables moron.
We'll see, f****it.
Problem is that you need to know the current involved to do that and need to know if the reason why the car that wont start wont start.
<reams of your even sillier more pig ignorant shit flushed where it belongs>
Sizing it for 100 amps should work fine. If you don't like that, just use my other method, look at the gauge size of existing jumper cables. Even you could do that. And no, you don't need to know why the car won't start, though that's certainly helpful. For example, we wouldn't want a moron like you to waste time trying to start a car with no gas or no engine.
BTW, not to change topics, but twice recently I was able to start my big Ford V10 (RV) with a dead battery and a power bank (Li-ion). These things are great. I have one in each car.
right, the answer is "it depends" as is the answer to so many interesting questions..
if the battery is good but just needs to be charged, a thin wire carrying a handful of Amps for a few minutes will recharge it enough to start the car. The actual starting current comes from the recharged battery, not via the cables.
but if the battery or connections are actually defective, and the current to actually start the car needs to come directly via the cables, heavy wire will be needed.
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He specifically said jumping a car to get it started. To me, that doesn't imply charging it, it's when you've left the lights on in a parking lot or have a battery that is going bad and use someone else's car to jump start it right away.
The problem there is that if you are really "jump starting" it, to me that means connecting it to another car's battery/alternator or similar capacity source. If you do that with a dead battery or mostly discharged battery like you can expect to find and a thin wire, it's going to melt the wire, because there is nothing to limit the current to just a few amps.
Most cables are about a 6 gauge wire, better ones are 4 gauge. You could double up a thinner wire. You also have to figure out how to connect for good contact too.
I don't recall the last time I needed to use them, but I always carry a set. I bet you do now too. You can get them for as little at $10.
Most wire size tables are useless for this. They are mainly for continious use where heat build up can cause a fire or melt insulation. Jumpers sized by those wire charts will be around size 0 or larger. Jumper cables are in open air and are only used for a few seconds to start most cars.
It takes from about 300 amps or more to start the small engines and much more for the large engines.
Number 6 wire is usually good enough to get most engines running if a quick start is needed because of a dead battery and a good engine.
It often helps if the battery is dead because the lights were left on for a while to have the jumpers hooked up for a short period of time to give the 'dead' battery a slight charge before starting the car.
I was referring to wire gauge tables that show resistance per foot of wire.
It don't think it takes anywhere near that. Typical car starter is ~1200 watts which is ~1.5 hp, so 100 amps is more in the ball park.
So, #6 wire has .0013 ohms per meter, .004 for 3 meters.
100 amps gives you .4 volt drop. 300 amps gives you 1.2 volt drop.
I would start with a 5 AWG if less than 10 ft length. Climb to 4 AWG size at least for a 12 ft length.
I made up 12 ft cables with 0 AWG size that always work.
The problem with small size jumper cables is not the overheating, but the voltage drop. If your source is low of power, it drops alone to 8-9 volts or less under strain, and adding a drop of 3 volts gives you only 5-6 volts at the receiving side ... useless.
Resistance of a cable:
R = rho * length / section
where rho is the electrical resistivity. If rho(copper) is given as
rho(copper) = 1,68 * 10^(-8) ohm*meter
the length should be in meters and the section in squaremeters. Cable can be made with aluminium (less weight):
rho(aluminium) = 2,65 * 10^(-8) omh*meter
For copper calculated values:
The suggested 5 AWG for 10 feet length would read as:
0,3133 mΩ/ft * 10 ft = 3,133 mΩ per cableYou need to sum up both cables resistance, that si
3,133 * 2 = 6,266 mΩ = 0,006266 ohmsFrom Ohm's law, the voltage drop would be:
V = R * I = 0,006266 * I
At I = 100 A you have only a 0,63 voltage drop. But if I climbs to 500 A you have up to 3,15 volts.
The suggested 4 AWG for 12 feet length would read as:
0,2485 mΩ/ft * 12 ft = 2,982 mΩ per cablealmost as above with the smaller, but shorter cable.
My 0 AWG 12 feet cables read as:
0.09827 mΩ/ft * 12 ft = 1,179 mΩ per cableand take up to:
I = V / R = 1 / 0,001179 = 848 amperes
before dropping 1 volt.
The trick with the Li-ion power bank cables is that they are very short, a couple of feet.
I agree, all of the above is consistent with what I said.
So, all this is for ICE cars. If you have one of those electric cars and you are out of juice, at the side of the road, what do they do? You can't just jump start it, you have to put enough charge it it to get it somewhere to plug in. So, what do they do? Like if you have such a car and call AAA what do they do? I expect it's tow you to someplace to plug in.
You pull out the portable wind generator and solar cell and wait for the sun to come out or the wind to blow. Just one of the green solutions of AOC.
Those electric cars may be ok for those that never get out of the city and only go 10 or 20 miles at a time. Now if they ever get them where you can recharge them at many places like all the gas service stations and pumps and in the time it takes to gas up an ICE car they may have something for me. The battery better last 10 years or more also.
Use some telephone station wire then, dingaling!
You get it towed to where it can be charged, or at most use a generator to charge it, but it needs to be a pretty decent generator to charge it enough to get far in a reasonable time.
See above.
Or load it onto a truck and move it that way.
Fucked, particularly in the depths of winter for the longer distance travel.
Me neither.
Not really except in the sense of the lithium mining etc.
Google this: car jumper wire minimum gauge
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