Technical Battery Cable Gauge Opinions Needed

Good morning everyone. I plan to place my battery in my trunk. Do I need larger gauge battery cables or are the typical two/ four gauge good enough? What gauge should I be using? Probably 10 feet from starter to the battery in the trunk.

(My stock flathead is converted to 12v)

***Please don't tell me that I'll need LONGER cables.*** I know you nut heads too well.

 

I like to use welding cables for this, with the good Tweco connectors. The typical 2 and 4 wont cut it. If you do a search, there are some other threads that may help. Good Luck

 

I looked for the threads. I found one of yours where you said the same thing. I might try it.

 

Run "00" welding cable with the good tweco connectors and you won't have any problems . I have that setup on my gasser .Never had any trouble .

 

Hilo hotrodder is correct... and what i use also...
at least ...---->\
http://www.taylorvertex.com/battery/cable-kits/

 

According to one of the flathead books, at six volts, a flathead starter draws about 45-60 amps. This chart should help you determine what you want to do...



The recommendation to go larger helps with current flow, and is how I usually do it. Just make sure you don't go any smaller than the chart shows.

 

depends, what engine? If it is something reasonble, then you should be fine with smaller wire such as 2 or 4 gauge. Some folks assume that every hot rod has a 13:1 compression big block in it, and say there's no way you could use anything smaller than 0000 gauge wire. They're probably right about their car, but not yours.

 

I think Grainger sells "00" welding cable and they are a couple of miles away from me. I'll check with them.

What about 1 or 1/0 gauge cables?

 

Squirrel has a point.When I said typical 2 and 4 , I meant the stuff you buy at Advance Auto. Welding cable has a much finer wire and can carry more current. #2 welding cable is pretty good. To be honest , if the motor is in good tune, you arent going to be running the starting motor very long at a time anyway, and a 6v starter on a flattie will spin pretty good on 12V. Its when the motor is hot, the starter is hot, things arent exactly right and you are winding and winding on the starter that you tax the system. I tend to overdo things sometimes. Good Luck

 

I see what you mean, Squirrel. Stock 239 flathead converted to 12v. According to the chart provided above, I should be using 6-10 gauge cables for 10 ft. This with out measuring current/amperage.
I do like the idea of using 00 cable because it's larger. But is larger always better. I really like this feedback from everyone.
I've built built cars before but I didn't move the battery around. Well, if you want to call them builds. More like V8 transplants. Pinto's. VW rebuilds.

This is my first build from the ground up.

 

I knew what you meant. Good advice. When I converted to 12v, I converted everything over including the starter. Because of the C-4 kit, I had to use a 1970 ford starter. I hated to get rid of the stock 6v starter but it went to a good home.

 

That's exactly what I use. HRP

 

I have been running Welding Cable for 37 years & no problem
and my Batt is in the Trunk
thats on my 50 Merc/327
just my 3.5 cents
or when the Cows
come Home!

 

whatever you use , i recommend running the ground cable all the way from the battery to the engine block and not to just to the frame. then from that point on the block run a ground cable to the frame. and then a ground strap from that point on the motor to the body. hope this makes sense

 

Put a starter relay in the trunk, next to the battery. That way, the big cable to the starter is only energised when you are starting the engine. A smaller wire works for getting power to everything else. And run the ground cable to the engine, near the starter if not actually on the starter.

 

I had twin fat cables on my build, but I ended up using the chassis type ground. I ran a normal gauge 20" negative through the trunk floor edge to the framerail. Then right at the battery neg terminal an 8 gauge body ground that is a foot long. Then a flat braided old type ground cable doubled up from frame to trans. Every spot was ground to bare metal, then star washers at each point.

works no different on my particular car, than it did before. Big early Olds motor too

 

1/0 welding cable, $4.03 per foot from McMaster Carr. make sure you also get the correct ends and use the proper crimping tool.

 

Good stuff here. Thanks you guy's!

 

http://www.taylorvertex.com/battery/cable-kits/ <----
---->
1/0 Gauge SAE Battery Cable Kits
980 strands of premium 30 gauge Copper Wire as our largest battery cable to deliver more Cranking Amp power with less voltage drop than most battery cables

1 Gauge Welding/Battery Cable Kits
770 Strands of premium 30 gauge Copper Wire with more flexibility and Cranking Amp Power than most OE cables

 

As you can see, some folks firmly believe that you should spend as much money as possible...



(my preference is to put the battery as close to the engine as I can, and use as small of wire as I can, and keep things light and cheap. That makes the car fast, too)

 

You might want to check the amperage draw of the flathead starter. I would have expected several hundred on a 6 volt system. I may be off but I am sure it is a LOT more than 60.

Charlie Stephens

 

Yes and using a late model Ford 12v starter also requires at least 300 amps from what I have been told for the solenoid [the one on the starter that kicks the gear out] to work properly no matter if the engine actually requires less..I use #1 carol welding cable since the 250 or so foot roll was free, otherwise #2 would have been my choice..

 

I think too large of a wire is just unnecessarily heavier, more expensive and thicker, making it harder to bend and route.

Once the wire reaches a certain size, it's not like an even bigger wire is going to get you any more electricity.

It's like pouring a 5 gallon bucket of water in the sink and another in the toilet. The one in the toilet will go down faster because it has a bigger drain than the sink. Just like the bigger drain, the bigger wire will handle more electricity.

However, if you poured the same 5 gallons of water down a 2 foot and a 10 foot culvert - it wouldn't make any difference. They would both drain at the same speed because they both have more room than they need for just 5 gallons of water.

So why pay more for a big, heavy, cumbersome, 10 foot culvert when a 6 inch toilet drain is plenty?

The guys who made the chart have figured out exactly what size wire is needed and what size is wasteful and unnecessary. I'd follow the chart.

The only advantage a larger-than-recommended wire would have is it would allow you to have a lot of broken strands or a lot that weren't making good connection. I can't think of any other advantage. And you can get away with a few bad strands.


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There's some basic Ohms law rules that can calc this out.

Generally I figure on 6v starters at 600 amps FLR (full locked rotor)

And half that for 12v starters FLR, or 300 amps.
Same energy, doubling the volatgae, halving the amperage.

Using yer everyday internet calc, a #1 AWG wire on a 10 ft run loses 24.8 percent - lets call it 25 percent - voltage on a 10 ft run in a 6v circuit - or in other words you have at the load - 4.61v.

Amperage doesn't do any work with voltage to provide "the push".

http://www.calculator.net/voltage-d...ce=10&distanceunit=feet&amperes=600&x=53&y=10

And of course at 12v approx 1/2 the voltage drop at the end of the 10 ft cable:
http://www.calculator.net/voltage-d...ce=10&distanceunit=feet&amperes=600&x=69&y=14

You can run that calc with your own numbers to experiment with options.
http://www.calculator.net/voltage-drop-calculator.html

 

In my 1949 Ford Flatty (My Avatar), I put the Battery in the Trunk. I ran 2 gauge wire to a Ford Solenoid mounted on the firewall. Kept the 6V Flatty Starter. It works very well.

VR&C.

 

er buck a foot light --->
http://quartermax.com/ultra-lightweight-8-gauge-battery-cable/

 

ha, ha, I knew it was aluminum.

I'm old enough to remember when low-buck aluminum house wiring came into play and hadn't been banned yet.

Better off salvaging old big copper ones from a diesel dumptruck. (like me) LOL "$zero per foot"

 

Great video, Henry. The add goes on to other you tube videos for making battery cables.

 

You're absolutely right, Charlie. On the initial kick (when the starter first engages the flywheel) the amp draw is considerably higher, just for a moment. Also at FLS/FLR, as Mr. Stutzer pointed out, the rating is 550-600 amps. Hopefully we are not planning to start an engine while in hydraulic lock, that would certainly require more amps than the conductor specified in the chart will handle.

A long time ago, in a galaxy not that far away (this thread, actually: http://www.jalopyjournal.com/forum/threads/flathead-ford-starter-amps.213977/) flathead31coupe measured his starter draw to be about 65 amps while cranking the engine.

Seeing as how Dave has converted to 12 volts already, that cuts the draw in half.

Wsdad is correct as well that increasing conductor size is only beneficial to a certain level...which all leads back to the almighty Squirrel's point of trying to haul ass with as little extraneous weight as possible!

 

Here is a good bit on making battery cables:
http://www.pbase.com/mainecruising/battery_cables
I just rewired my charging/battery system on my diesel powered sailboat using this as a guide
You can also find the crimp on style battery cable ends that you would use for cars on the net
Another good article on crimping terminals:
http://www.pbase.com/mainecruising/wire_termination
http://www.pbase.com/mainecruising/terminating_small_wires
Also when figuring out wire length/gauge , you need to double the length....in other words , a battery 10' away is actually 20' run on the chart...10' for the + and 10' for the -