Battery jumper cables and terminolgy of CCA

wintersun wrote:

Harbor Freight is a place to get something that you will use once or twice and then toss and not for anything you need to be able to rely upon to work when needed.

gee I guess I will have to toss out a whole bunch of stuff that has served me well for years.
bumpy

Wayne Dohnal wrote:

I thought that the electricity was carried on the outer surface

Not applicable at all to DC, and not applicable to 60 Hz. AC until the conductor diameter approaches 3/4 inch.

It is carried through the core of the copper and the capacity of the wire is a function of the area of the cross section of the wire, not its diameter. Distance also affects the voltage drop along the run so the longer the cables the thicker the gauge wire used should be.

With a dead battery there is already resistance working against the good battery and thin jumper cables only make the situation worse.

Harbor Freight is a place to get something that you will use once or twice and then toss and not for anything you need to be able to rely upon to work when needed.

With Playtoy jumper cables, you are committed to exchanging time for purchase price. With a larger engine or diesel it may take A HALF HOUR of boosting for enough amp hours to flow into the depleted battery before it or they have enough power to crank the disabled vehicle.

There is no way in hell Playtoy cables can jump start a vehicle (RV) that has a bad battery. They "might" start a toad that has a 4 cyl engine that has a gear reduction type starter motor.

Jump starting with cables connected does cause an incredible amount of transient voltage spikes to be seen on the running vehicle. Check your owner's manual to determine how freaked-out the manufacturer is about this. Blowing a 500 dollar ECU plus incurring a tow bill is a hell of a price to pay for being a good Samaritan.

I made my own jumpers. 25'x 2 of 00 gauge welding lead with $70 clamps from NAPA. They are heavy but will jump about anything. they will reach from the truck to the house batt on my 5er toy hauler.

MrWizard wrote:
"Skin effect" As it is called is a, special situation with extremely high voltage

nope, skin effect is a function of frequency, NOT voltage, and it applies at any frequency above DC. Just a matter of degree. As mentioned earlier, at 60Hz, don't really have to take it into account until conductor diameter is about 3/4". It IS something that power companies care about with HV transmission lines, not because of the voltage, but because of the cable diameter needed for the current the lines carry.

while the above post has a quote about skin effect being an "odd" effect, it really isn't that "odd" at all. It's very predictable and follows all the "rules" of electromagnetics that govern how current flows.

But, in most cases, working around AC power sources, audio, etc. it's not something that you need to take into account.

Back to the OP. Just remember, you get what you pay for. While I will admit to shopping at harbor freight, and there are things I get, use and like, one must be careful.

They aren't the only ones selling copper clad aluminum jumper cables. figure a CCA jumper cable is the same as at least 2 sizes smaller copper. For example, 12 ga Al. has about the same resistance as 14ga copper. or 12 ga aluminum has about 50% more resistance than 12 ga copper.

MrWizard wrote:
"Skin effect" As it is called is a, special situation with extremely high voltage

Actually HIGH FREQUENCY more so than high voltage.

Skin effect is not at play at DC or even low frequency AC only becomes an issue when you are playing around with RF frequencies as in radio transmission or broadcast (although skin effect starts to happen at low frequency AC typically no special measures are normally needed to deal with it).

I found a very good explanation from Beldon Wire HERE which has a rather nice write up.

Here is a short quote from the above website..

"Skin Effect happens in all wire and cable (or in any metal object that conducts a signal, such as a trace on a circuit board or antennas, etc.). When the "signal" is DC, it uses the entire conductor, with the same amount of current flowing in the center of each wire as on the outside of the wire. As the signal changes frequency (i.e. is now a wave changing direction) a very odd effect occurs: the signal begins to move more to the outside of the conductor than the inside. For audio frequencies, which are pretty low frequencies in the spectrum, this effect is so tiny it can barely be measured. Table 1 below shows how much conductor is used at 20 kHz, pretty much the highest audible frequency, and compares that to various wire sizes. "

I would highly recommend folks to look at the above website and read the entire article.

As far as the jumper cable the OP bought, under normal circumstances it will most likely be fine for jump starting a small vehicle engine but if dealing with a bigger V8 or Diesel I would opt for a heavier set of 100% copper cables..

The copper coating is simply not heavy enough to overcome the weaker aluminum. You have to step up several gauge sizes in aluminum to get the same current capacity as 100% copper.

I have jump started my car with 10ga (Copper superflex but 10 ga)

how to jump start with light weight cables.

hook up,
Remember when hooking up jumper cables the last connection is always a Chassis Ground and made to something NOT close to the battery,, DO NOT make the last connection to the battery... Try to be at least 1-2 feet away minimum. (As far away as you easily can do it)
Run the DONOR car's engine a while (like 5-10 minutes) then try to start disabled car.

When disabled car starts disconnect STARTING with the last connection (the one not near a battery.

Why do it this way.

It is not unheard of for the disabled battery to "Gas" a bit (Donor too) when jump starting, this Gas is 2 parts Hydrogen to one part Oxygen.. The exact ratio for making one BIG BOOM if you add a tiny spark.

"Skin effect" As it is called is a, special situation with extremely high voltage

Probably more like #10 wire, at least most I see at those prices look like #10 conductor. I have 2 sets of old Sears cables that have #4 conductors. :)

I thought that the electricity was carried on the outer surface

Not applicable at all to DC, and not applicable to 60 Hz. AC until the conductor diameter approaches 3/4 inch.