I need to place my battery 7.5 feet from the engine. Cables seem expensive. Could a welding cable be used? Might be easier to access. Thanks
In almost all my projects I put the battery in the trunk using welding cable. I use #2 most of the time and have never had a problem.
I always buy mine from the local welding supply store. They have the ends and will crimp them on for free. Most of the wire is black insulated so you need to mark the positive end at the battery with red electrical tape or maybe a red zip tie.
Battery Cable Gauge Opinions Needed ^^^ No disrespect but the search function can answer your questions???
Hasn't been that long ago that a really exhaustive thread on battery cables was going. Kave you done a search?
Battery cables are like sheets...the higher the thread count the better the sheets....same with battery cables, the higher the wire count the better electricity flows...or so say my electrician buddies.
That's not true Ron. The current handling capacity of wire is not increased by the number of strands in the cable, or no strands at all (solid wire). More wires can make the cable more flexible, can make it more resistant to breakage, but does not increase the current handling capacity, period.
Have to disagree, the outer portion of Each Wire, count em, conduct the charges. The electrons repel/propel one another. So they seek a region or path that makes for easiest p***age. I've read many times of this discussion. Tests would prove out which serves in any event.
I agree...current does not travel through the strands in flows down the outside of the strands. The more strand count per inch, so to say, the easier the current flows....again, or so says my electrical buddies....they may be wrong but they wired Diablo Canyon nuclear plant and since Im a pipefitter, not an electrician, I would defer to them.
Just did a google search on this subject and find as many arguments one way or the other....seems not even EEs can agree on this subject, so considering, Im just a dolt, I will bow out and let the electricians hash it out. Ha
No guys, the entire conductor carries current, not just the outside of the strands, that is a gross misunderstanding of the physics. A 00 gauge cable has the same current handling capacity whether it is stranded or solid. Period. There is such a thing as "skin effect", but it effects very high frequency alternating current, higher than the audio range so it really doesn't effect audio quality either. For direct current forget forget about it. Use stranded for flexibility and breakage resistance, not for increased current handling. That is fact.
By the way, electrons don't repel/propel each other either. Electrons are drawn through a conductor by difference in potential (voltage). The common modern theory is the "Hole Theory", where electrons in the outer rings of an atom move from one atom to another. As one electron moves, it leaves an opening (a hole), which draws a nearby electron to fill it, which leaves another hole, which draws another electron to fill it, and on, and on, and on. Electrons move in one direction along the conductor (negative to positive), holes move the other direction (positive to negative). When you get to the point there are no more holes to fill, there is no potential, no difference in voltage, and current ceases to flow. Google it and fact check me.
Welding cable is excellent. Be sure to install it so it won't rub, chafe or get pinched between the body and frame or suspension. Inside a plastic conduit would be best.
One cheapie way is to buy two sets of cheap 8-foot jumper cables on sale. They are about 4 gauge. Split them - use two red and two black wires. That gets you the current of one much thicker wire. Sometimes around this time of year the chain stores will put them on sale, it becomes cheaper to buy these than the same wire without jumper clamps.
I have 30 foot welding cable jumpers which are awesome. I put them together to accommodate a motor home. Skin effect is frequency dependent. At dc to house current 50-60hz, the electrons flow within the entire conductor. At radio frequencies they travel on the surface and pipe is often used. Skin effect aside, welding cables are way more flexible. And expensive too. $5-$10/foot and available in red and black.
The ***umption here is that you are playing with 12 volts. If the system is 6 volts, then definitely look at the larger gauge wiring.
If we're going to get picky down to the quantum level and things like skin effect, it maybe should be pointed out that welding cable isn't (technically) rated for auto or marine use, or more specifically the insulation on the wire itself is not (EPDM) with regard to abrasion and chemical (oil) resistance and such. It's probably not a factor or unsafe, but dedicated auto battery cable isn't any more expensive to have custom made. A 36" 1/0 AWG pure stranded electrolytic copper with terminations of your choice is about $20 delivered, maybe double the cost of drugstore el-cheapos, that won't work at all anyway, or suffer significant voltage drop. The wire itself measures .397" diameter, hefty stuff.
Welding cable would be my choice, and if TOTAL cable length (both positive and negative cables) is under 10', #2 will be adequate. 10' to 18' total, you'll need to step up to 1/0. Above 18', then go to 2/0. This will keep voltage drop close to or below 3% for easy starts, ***uming a 'typical' 250 amp starter current when under load. As to the 'rating' of welding cable, it's pretty tough stuff. If you drag a thermoplastic-insulated wire around on a concrete floor for days, it won't hold up nearly as well as welding cable. Most welding cable is pretty chemical resistant too. What it doesn't like is extended periods of high heat as the insulation will break down, so care in routing it to avoid heat exposure is critical. Heat and long-term sunlight exposure is what kills welding cable insulation. Now, as to the fine-strand vs regular strand wire and how much current they can carry, there is some truth to that but not in the way you think. While welding cable is fine strand primarily because of it's much better flexibility and resistance to breaking, under certain conditions it can carry more current 'safely'. There is some truth to the idea that current flows mostly on the 'skin' of the conductor. Under extremely high currents, the 'leverage' presented by these high 'skin' currents versus the low internal currents can cause the wire strands to physically deform and move. Yeah, I thought it was BS too, until I saw a safety film that showed a 'regular' 4/0 cable thrashing around like a runaway fire hose under extreme current. The fine-strand wire presents much less leverage, so less movement. But for a given size in equal total circular-mil area under a continuous load, both types will present pretty much the same resistance, the same voltage drop, and the same amount of heating when conducting the same current.
1. While unimportant here - I happened upon the skin effect numbers for stranded wire and was surprised they can start becoming a factor in the AUDIO range. http://www.powerstream.com/Wire_Size.htm 2. Numbers check for your choice of AWG 2. The wire is rated to carry around 180 amps. A 12v starter will draw around 100 amps. So far to good - don't want to melt the copper wire. Voltage drop for 15 feet (over and back) is about 1/4 volt (0.16 ohms per 1000 feet/15ft/100amps) - You need at least 12v to start the engine, starting with approx 12.4v at the battery. Also good. Lastly, heat of about 25 watts (1/4 V x 100 amps) can be easily be dissipated over that distance without creating enough heat to melt the insulation. Good job. Send pictures
That chart is misleading; the 'skin effect' numbers given are for SOLID conductor wire, not stranded. And the 'typical' V8 12V starter draws about 250 amps under full load, not 100 (the starter on my 1100CC motorcycle draws 90 amps...). The starter load can vary, but for a V8, low would be around 200 amps, a big-inch, high compression motor could draw upwards of 350. This is for the 'typical' OEM type starter. A modern permanent-magnet, gear-reduction starter can lower those numbers some, but not by a big bunch.
Thanks for the learned numbers check Steve. I couldn't find a decent current spec for a 12v starter except one measurement at 100A on which does seem low. Personally I would opt for heavier battery cable than 2awg but it will work. Marginally. And marginally doesn't cut it when you have problems with a balky de-tuned cold engine. Incidentally that skin effect chart is quite clear on it being solid conductor. That doesn't change anything except my previous ***umption and surprise about skin effect frequency is actually several orders of magnitude lower than I thot.
****,even Sheldon would say welding cable would be fine! If you can only find black,use a bit of red heat shrink on the positive side.
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