Relocating the battery in my 40 Ford coupe to the trunk, what size cable (gauge) do I need to use? Thanks!
Check the Internet, it's got wire size charts all over ! 6 or 12 volts ?? 12, I'd use "0" 6, I'd use volts I'd use "00". I just got done wiring one car, front to rear, and rewiring a car with just the charging system. Both are 12 volt, both have "0" cable running from the solenoid in the front, to the battery (master cutoff switch actually) in the back. "0" for long runs hasn't failed me in over 35 years of moving battery's to the back. Some use welding cable, It's NOT made to be in oil soaked environment. You know...leaking oil pans, front covers, etc. I just spend a coupla dollars more and buy "actual", high strand count..."battery" cable. Mike
https://www.jalopyjournal.com/forum/threads/battery-cable-size.1217706/ Lots of good info. I'm going to run welding cable.
thats how I do it, battery needs to be as close to the starter as possible... but some times the rear is the only spot, and sometimes you want the weight back ther...voltage drops quick with small cable
I generally use the largest welding cable I can find but when I looked at what came from the factory in my trunk mounted battery in my Miata, It was only about half as thick.
I’ve done this to all the ‘40 Fords I’ve owned. I used welding cable thinking heavier is better. I’ve also ran just 1 positive full length of the car and grounds at front & rear. I’ve had best results with running both positive & negative 0 gauge new full length. As others have said welding cable is exactly that, for welding. By the way my cars have always been 12 volt if that matters. Good Luck!
I spent a lot of time gathering opinions and guidance on this and decided to go with six feet of 0/ welding cable for positive and negative from the 12V battery relocated just behind the passenger side of my '29AA cab. But I haven't stopped there. I made sure I ran the negative cable directly to the block, ran a woven ground strap from the block to the frame and to the body - in several places - and then ran dedicated positive and negative #8 wires to the fuse box near the dash. I'm also going to run a dedicated ground wire to the headlights and horn. Overkill like hell, but you know what? There will be far less chance of a bad ground wire screwing with my electrical system.
Some of your decision is going to revolve around what amperage your alternator is capable of producing. You also need to realize that the longer the cable/wire in any circuit, the more resistance to current flow. You may need to upgrade your alternator depending on whether you are going to have A/C and maybe running 1/2 radiator fans. I'd get an alternator that has excess capacity for your needs, maybe in the range of 100 amps and probably a main cable thats a 2/0 or larger. Just kind of depends on your particular choices of what electrical things your car will have.
Also you should know the fine strand copper cable is rated much higher amperage than regular electrical wiring. So don't look at the codes for normal coarse strand TW or THHN wire. A 2/0 welding cable or fine strand copper cable is rated 400 amps, where 2/0 coarse strand copper is rated 175 amps.
The #1 place to get the best USA made cable and also great pricing with fast shipping https://www.batterycablesusa.com/?g...yZSPTCvkR3ylbL7unih_PxH9lFcflgvhoCwDoQAvD_BwE
I bought a “kit” on jegs. Just installed it yesterday in my 40. I believe the wires are 0/1 gauge. It fires it up no problems.
Battery cables USA for me also you need alt size and electric fan draw (if using) also it's called welding cable for a reason (just sayin)
Good stuff One thing to remember, when going for trunk mount with weld cable, It is prone to be droopier than regular battery cable. So plan on more securement ( support )
This is correct, but not really applicable when it comes to wire size from battery to starter as this is going to be larger that most alternators would require. Quick math, big alternator: 100-200 amps. Big battery: 700 cold cranking amps +. To be safe, I would run a 1/0 battery cable and then base the alt cable on the output of the alt and length of cable. If in doubt, run a 4ga cable from the alt to the starter and 1/0 back to the battery, should be plenty for just about any full-size car that I've come across with all the modern accessories.
OP never told us whether his 40 is equipped with an Allison 1710, a flathead, an SBC, or ???? so like I said, we can only guess. The answer should be somewhere in the #2 to 2/0 range.
The current flows on the outside surface of an individual strand of wire. Therefore, a half inch diameter cable with many fine strands will have much more surface area than the same OD with bigger strands. Or one strand.
(hence upsizing the wire) This is for a conventional underhood battery location. If you move to the trunk, then upsize from the recommended size. Grounds............. As @PotvinV8 pointed out, and also pictured below,the wire from the battery to the starter is larger (whether you use a disconnect or not).
does that work on DC, or only high frequency AC? Just seeing if we need a little bit of myth busting here.
True the 6 volt need larger cables than 12 volt but you are one hell of a lot better off to just spend a few extra bucks and buy 2 ought or larger cable and forget the 4 ought crap because those size 4 cables are very often the main issue if you have a hot start problem with a rig especially if it has a 350 or larger engine. That was the hot start problem with the 454 in my 1 ton even after I did the Ford Solenoid thing that helped but didn't fix. Volts, amps, ohms = water pressure, flow, diameter of the hose or fitting. The same reason that you can fill a gallon jug with the outside faucet than with the kitchen sink. The amount of restriction.
It's mainly for the longer distance to reduce resistance. As far as some recommending huge alternator battery wires, I'd like someone to show me any factory cars, even with 100 amp alternators) that use that size wiring? Almost every factory car uses the finer strand wires, even in small gauge wiring, and they do this to allow flexibility so wires don't rub through or break easily. But since the wiring is fine strand it also has a little higher ampacity than equal gauge coarse strand wiring. I've never seen a factory alternator with a battery wire larger than 8 awg, and mostly 10 awg or even smaller. I use 10 awg on all of my alternators and never had an issue.
Not much load to start a baby 4 cyl. The basic rule is that when voltage doubles half the amps are needed so a smaller wire works. The amps do the work. Think of it like a garden hose. Pressure = volts Volume = amps. Up the pressure (12 volts) and you you have more volume (amps) being pushed to do the work. With reduced voltage you need to increase the pipe diameter to get the same amount of amps delivered to the job.
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