Technical Changing location of Bat to trunk/ Ga. of wire?

Want to move my battery from the firewall to the trunk in my 40 Ford sedan w. SBC mild performance Want to go with heavy gauge bat cable , maybe even a bit overboard , Suggestion ? Gene

 

Go to Tractor Supply and buy heavy welding cable. They have the cable ends there, too. Get battery terminals at auto parts store. Run ground cable to at least a rear bolt on the transmission if not to the engine. Put good battery disconnect switch under seat or within easy reach of the driver.
Good luck.
Al

 

Batteries really like to be close to the engine....I wouldn't move it without a very good reason.

 

If I was going to do something like that I'd use minimum 2/0 or 00 aka "double-ought" gauge cable already made up, maybe bigger. The crimp connections are critical. The replacement bolt on terminals sold at the parts store will almost certainly drop way too much voltage. Can get cables made up any length or end terminals you want. EBay has some pretty good vendors, just search "00 battery cables".

 

In using the "Search" function, there's a LOT of reading on the subject.

Mike

 

I relocated my batt to the trunk in my '54 and used twenty feet of 1/0 copper welding cable. I got everything from these guys and can't say enough about them!
https://www.batterycablesusa.com/

Top quality 'made in usa' products, great prices and their shipping is crazy cheap! $3.97 flat rate! They've got everything you'll need.

 

I like to see big cable, especially if going any distance (over 10 ft) or running a ground wire back. The 'average' V8 starter draw is 250 amps which is about 4 HP. Just a 1 volt drop will increase current by over 20 amps so having the 'extra' capacity in a hard start or low battery situation can make a difference. I'd use 4/0 for a trunk-mount battery.

 

Some info, ensure engine is earthed to frame as well as battery

 

Squirrel is correct, long extended cable runs are not optimal for battery performance. Think of all the problems we read about with the starting and charging system with the battery and cables directly at the engine with short cables. I would expect problems particularly if the frame is used as a return path. This would be also true for alternator output, the ability to supply current drops off a cliff with just a tiny bit of excess resistance, barely measurable. The figures I've seen published are an extra 10 or 12 tenths of an ohm will reduce alternator output by about 30%,

Maybe if the frame and everything is new it would be OK for a while. Sort of like the OEMs, once corrosion starts to set in problems start to stack up. If careful attention is paid to voltage drop on both POS and NEG sides it should be OK.

 

doesn't apply with sbc but might help a reader...
years ago my brother and i ran flatties with 12v systems , they tried to pull the ring-gear off, even had one tacked on at the machine shop...
last flattie i put the batt in the trunk and ran 4 ga. cable, smallest i could get and work, it and the longer cable reduced the 12v to the flattie starter... kicked in slower...

 

1994 I used number four nickel plated cooper on the coupe. Has never had an issue with starting. Used star washers on grounds and studs. Used an Optima battery. First battery was changed after 9 years just because it was 9 years old. Good grounds are needed in more than 1 location.

 

I ran 2-00 cable from the battery to the starter. I got everything I needed from these guys. https://www.elecdirect.com/electrical-wire/battery-cable
Of course I bought my wiring and connectors about 6 years ago and the prices were much lower than today's.

 

There's always lots of debate when it comes to remote mounted batteries, and the cable type or size. But always use fine strand battery, or welding cable to get the highest amp rating. Standard cable in 2/0 vs. fine strand 2/0 have huge differences in their amp rating. Not a big deal when the cables are 3 ft. long, but when they're 10-12 ft. it sure is.
I personally use 2/0 fine strand battery cable, and buy it on the internet for much less than I can ever find it for locally. I own a Greenlee crimper, so I also buy crimp ends, and I use side terminal batteries with 3/8" threaded terminals for my builds.
All my hotrods get trunk mounted batteries, as I prefer not having my batteries under the hood with all the engine heat. Plus it just looks cleaner not being there, and the weight over the right rear tire helps a tiny bit too. I also use a safety battery cutoff switch on all my installations.

 

2/0 for carburetor and mechanical fans... or 4/0 for e fans and possibly fuel injection.
My general rule of thumb if doing it in the trunk..

 

All my 3 hot rods have the battery in the trunk with 00 welding cable. I also had the battery in the trunk of my 40 Ford sedan with 00 and NEVER had any trouble starting the cars. The cable has gotten expensive though as they are copper. The cool thing about the 40 sedan, there is a tack welding original cap in the floor of the sedan so all you have to do is remove the cap for the perfect hole to run the battery cable through. Removing the battery from the engine compartment might be why my 40 sedan always ran cool but I did love the clean look more than anything with the battery gone. Just my experience.

 

There's nothing wrong with long runs as long as the cable is sized appropriately. It's when you 'save money' with undersized cable that problems can crop up. And using the frame as a ground path is fine too. While steel is a poorer conductor compared to copper or aluminum, as long as the cross-sectional area is enough (and virtually any vehicle frame will be plenty) it'll work exactly the same.

Of course, proper terminations are critical but that's the case regardless of cable length/size. If deciding on a remote-mount battery, I'd weld a couple of 3/8" rod couplers into the frame to give good secure grounding points.

 

Right - it's "fine" in theory but in real life only so long as everything is gauged up, and the terminal connections, grounds & other connections are not corroded.

 

That's always the case, cable length is usually the smallest part of that. There's cars out there with factory-installed trunk-mount batteries that work fine...

 

I’m not speaking for anyone else but 40 Fords and Tri-5 Chevrolets have shitty battery locations and look better moved. From what I’ve read here moving them to the trunks and done properly is not detrimental. We kept the battery in the truck of sons 40 Chevrolet because it’s been there since 1962 when it made into a gasser. 2/0 welding cable.

 

My neighbor's later 70's Mercedes 450-SL has the battery in the trunk. It's been there since the car was new, it starts and runs fine and he's never complained of starting issues that I know of. Only a guess but the cable didn't look all that large, maybe 2/0 gauge?

 

Which is absolutely the same truth for a battery in the engine bay. I was just dealing with that in an OT vehicle. The battery is new (agm) and sits 18-24 inches from the starter and there were cable and ground issues.

 

ALL the stuff above and
...........DON'T run the cable to the solenoid 'still in the engine compartment'! Move it too or....eliminate it with a more modern starter (you don't need both!)
I grounded mine in the trunk to the frame. I ALSO grounded the starter to the block and the block to the frame AND the body. Ya can never have too many grounds.
I mean ground 'clean' to bare metal grounds. Once grounded then paint over them.
6sally6

 

I guess I should add that I also run a ground 00 back to the bell housing. This way you only have four connections and I have never had corrosion problems.

 

I’m running 00 welding cable for my trunk mounted battery on my 31’. It’ll be about a 6-7’ run under the car in a tube to protect it. But will run to a relay then the battery. This way it’s only hot when starting.

Also, look at what your starter manufacturer says about long battery cables for their stater.

 

Well that's what I was getting at. The factory installed stuff always works fine, at first. They treat copper like it's a precious metal and cheap out on gauge size. Add in a few years or decades of road salt and corrosion and even the short cables run into problems. The people doimg this on their own generally spend the money to it right, like this guy here.

 

Every single connection in any electrical wiring adds resistance to the circuit, so need to minimize connections, and also make sure they're all as good as you can make them. Bolted or clamped connections are the worst sources of resistance, and need to be clean and tight. Butt splices, or crimped connections work extremely well if the right tools are used, and properly installed.

 

Welding cable will work but it far more expensive then regular battery cables. Welding cable is just more flexible something that is not really a issue in automotive use

 

Steve & 6sally6 have it correct. 4.0 fine-strand welding cable, & be done w/it. Including the grounds - which are at least as important as the so-called "hot" side. It's for the current-carrying, not flexibility that we're after. I'll add: on your battery cable connections: sand them shiny, internal starr washers are ok, & you should properly torque the bolts/nuts so they don't loosen up, = heat, = trouble you don't want. But absolutely necessary is the anti-corrosion stuff. Use Super Lube(reg stuff ok, you don't need any of the spl versions), & coat "*everypart*" of each connection inside & out, & then a thick coating over everything assembled. Like the govt is paying you a taxfree bonus to do this well. W/this stuff, DO NOT get it on your clothes, as it'll get into the washer & transfer to your other wearables. & wife, +you, will be very unhappy! I use nitrile gloves. paper towels, & brakeclean to clean up with. Nothing else(well, a pressurewasher will remove most of it) takes it off, but the connection will last for ~ 2-3 years in everyday usage, & will still be clean inside after that. Been using it on city busses for 10+years. If I had brains, I'd own stock.... . I'd also solder both the flattened & crimped ends of the cables, then use at least 2 layers of hi-quality glue-filled shrink tubing. Long one(like 6-8"+) on 1st, then shorter one(like4"+) over that to reinforce the crimped joint, to take any possible flex from vibration out of the joint area. Not quite bomb-proof, but not far from it. I don't like soldering electrical connections, but on these I do - in an attempt to totally seal them from elements, incl salt - which will eat it's way thru the tiniest opening available, which also trouble. Overkill? Maybe... sorta... almost...
Marcus...

 

I have to disagree about the cables not needing to be flexible. If the author of this thread is doing a 40 Ford sedan, when he goes up through the rear trunk floor it's nice to be able to make the sharp bend. I also believe that when something is flexible, it won't crack as easily. Airplane wings are made that way, very flexible.

 

Not only that, every connection or connector is a potential source of failure, and what that really means is it will fail, eventually, it's just a matter of when. Auto environment is pretty brutal for electrical connections. It's amazing that the lights and signals and starters and all that stuff sort of works for as long as it does. The only time most people ever pay any attention to them is when a connection finally fails. Then they pay attention.

Even Star Washers have been superceded or replaced by better ways of making a connection. The OEM used them because wanted a quick way to get a reliable electrical connection through layers of primer and thick paint (and especially through the warranty period) and they do work for that, but there are better ways, electrically speaking.

I like NO-OX-ID to coat everything a small can will last forever, good as a kind of anti-sieze too. Vaseline is mentioned in all the older manuals. Anything to keep out moisture and road salt will help a lot.