Battery relocation question... amperage drop?

I did a search but didn't see this aspect of relocation addressed. When you relocate the battery, do you have to do anything to account for the distance or length of the new cables? Will there be a drop in cranking amps depending on distance? I'm only going either into or under my pickup cab (still undecided) but wanted to be ready for any issues before I started moving things.

 

you worry too much

 

LOL...just wanted to make sure I'm not going to have issues...maybe I do worry too much. I'm a perfectionist and sometimes I get lost in the details...

 

Use 6 volt cables to relieve your concerns

google

 

you should have no problems with this, It also makes it easier to hide cables and wires in that location.

 

That one is a Cake Walk !

 

Just don't run the wires above of next to the exhaust pipes... Heat raises the resistance.

 

The battery work best if its away from heat. Mines in the back and its like a kid in our generation. Its there but you don't know it. We loved the kids bit they don't need to be in our face. Ice man

 

ive always been told as the wire gets longer, you should use heavier wire......?



skull

 

Of course it matters. Whether it matters enough to affect the operation of your starter depends on several variables.

It is not as much that the amps are reduced since the current is the same in a series circuit. It is that the voltage is reduced at the starter, which means that for the same current less power is available to spin the motor.

From Ohm's Law, we know that in a DC system the voltage drop across something, like a length of wire, is the current times the resistance.

So, let's say that your starter pulls 100 amps, and that your battery cables have a resistance of one hundredth of an ohm per foot (these are just made-up numbers to illustrate). If your battery cable is one foot long then the voltage drop across it is 100 times .01 times 1, or 1 volt.

Now, if you move the battery to the trunk and use cables ten feet long, then the voltage drop is 100 times .01 times 10, or 10 volts.

As you see, higher values of resistance due to either smaller-gauge wire or longer runs have a great effect when you are talking about large values of current.

So a rule of thumb is to go to larger cables if you have the battery further from the starter. Note, this is for the hot lead as the ground is to the frame, and the frame/body is effectively a hu****ous gauge wire.

This is why animals get can get zapped when lightning strikes the ground even though their owner standing next to them is OK. The lightning sends tremendous currents through the ground. Even a little ground resistance results in huge voltage potentials per unit length in the ground. Animals feet can be farther apart than a humans, so the zap factor is bigger for them. Also, they have 4 feet on the ground so are more likely to be standing normal to the flow of current through the ground. There are cases where two people are standing next to each other when lightning hits, but one person is standing with their feet perpendicular to the others. The voltage gradient is larger for the person standing with their feet aligned with the direction the current is flowing through the ground.

Note - you can run a thicker cable (the amount of copper conductor, not just thicker insulation!) OR you can double up your skinnier wire.

 

I just bought a 900 CCA gel battery for my 57. The battery is in the trunk and I used airplane booster cables. No shortage of power at the starter and that 454 winds over like mad.....

 

dang plym 49 you hurt my brain,anyway there was a thread on here about using welding wire for batt relocation,maybe help,

 

can't find it with search,anyone remember?

 

This is for my '56 Chevy pickup. I was considering mounting it inside the cab...my main concern being outg***ing. Under the cab makes more sense but accessibility becomes and issue and the potential for things being kicked up from the road and causing damage is an issue as well...not matter how strong the battery box. It seems that there might be more room under the bed AND the battery may be better protected...I'll need to look into that. It would be cool to see what other pickup owners have done...

Thanks for the great info guys.

 

Good old voltage drop. If you're not going too far with the battery, go to the parts house and get a cable that'll connect it up. Some of those are what I'd call very long and they still work fine. I never dissected one, but the gage of wire is probably a bit bigger as the length increases.

Going to the trunk is another story, welding cable works for many installations. I once used this piece of aluminum core plastic coated wire on a stock car that worked very well. The wire core diameter was probably close to a 1/2".

Bob

 

I have many years experience in high end audio and we routinely relocated batteries. You should be fine with 4ga cable for where you're going, any stereo shop can sell you the cable, ends, fuse holders and fuses to get it done. part***press.com has good prices on stuff too if you are not near a decent stereo shop.

 

we moved my boss's Sedan Delivery battery to just behind the right rear tire..never a problem. It's tucked up in the quarter panel due to the fact theres no place inside to hide it. Works like a dream

 

You can put the battery far far away, use fine stranded wire (diesel locomotive type) and make sure you run the block ground jumper to the negative battery to match the big red wire to the starter.

 

You've got it easy with a 56 cab. I mounted my battery on the outside of the frame rail(it will fit between the frame and the inside of the step panel, just a little behind the starter. ) I used a drop down Stainless Steel box and also installed jumper posts in the cab, behind the p***enger side bucket seat. My truck is lowered, so that way if I ever had to jump it, it would be easy to open the p***enger door and connect to the posts. You are just as close to the starter , if not closer than original. My truck is a 58.

 

Watch where ya run the cables. I put the battery in the trunk and ran the cable under the seat to the back of the console. I got to bouncin' a fat chick around in the back seat, and set my friggin' car on fire! Don't do that. OK?

 

Old Audi's had a plastic bridge over the pos. terminal to prevent that very problem. They were mounted under the seat from the factory. I used one in my first 34 P/U because they were not as deep as most batteries. Even the after market replacement batteries had the insulator bridge. The battery box was no lower than the frame bottom but still did not extend up too far under the seat. I've always put the battery under the seat of my P/Us. You can run a short ground cable to the tail shaft of the trans and therby reduce the voltage drop of a longer ground cable. Not much you can do about the pos. cable except run a heavy one. And yes you will need a ground jumper to the body but it doesn't need to carry the starter amperage so it can be much smaller.

 

Yes, longer distance will reduce cranking power, but under the cab isn't much, starter is right there nearby. You'll probably be fine with a normal length batt cable. Actually it might require a shorter cable....................I moved my battery from under the floor to motor side of the firewall, required a longer cable. no worrys

Perfection to me is having everything out in the open where I can work on it, so for me uder the cab has it's downside, but I understand people that want to hide the battery. Each to his own.

Not true. Battery likes heated environment. No advantage to move the batt for that reason.

I can understand moving it for weight distribution, look, etc., each to his own. Accessability is primary for me.

 

Any pics of your setup...including the jumper posts?

 

I'll take some pictures tomorrow(todays grandkids day) and get my son to show me how to post them. I took the gas tank out and mounted the tank behind the rear axle, up between the frame rails. If you open the p***enger door and look to you left, back in the rear corner of the cab, there is a flat place and that is where the post are located.
Will try to post pictures tomorrow.

 

Trying to get pics to post

 

trying posting again

 

I think I got this posting down. As you can see, the battery posts are easy to get to. I just had to add a few more pictures. The battery is mounted to the outside of the frame, directly below the p***enger bucket seat. You have plenty of room between the frame and the step panel.

 

The original cables should have been sized properly to limit voltage drop. When you relocate your battery to somewhere else and the cables need to be longer then you need to go up in your wire size (a bigger wire will have a smaller number gauge like 4 gauge being smaller than a 2 gauge, a 2 gauge being smaller than 1/0 and so on).

If your relocated battery could use the original lengths then go with what was there originally. A closely mounted battery to the starter would only maybe take a 4 gauge and then the same sized gauge wire for a ground from the engine block to the battery negative terminal. If the battery was in the rear of a vehicle and the cable lengths were 12-15' long each then I would maybe run with 1/0 sized wire.

Since most engines are mounted on rubber mounts you need to tie either the battery negative post to the body of the vehicle or tie the engine to the body of the vehicle. This is for anything grounded in the cab, firewall, trunk, radiator support and so on can be tied back to the battery and alternators negative. For this connection you can use the braided ground straps or an 8 gauge wire.

I'm not a fan of using the vehicles frame as a negative return path. My reason is steel is a poor conductor of electricity. By running a cable from the battery to the frame and then up front run yet another cable from the frame to the engine you have increased the amount of connections and with multiple connections one or more can become poor and give you problems. I've seen some done this way and the person has never had a problem but I've seen others and they have had all kinds of problems. A lot of it too has to do with how well the installation was.

If you go with custom cables (wire), crimp on ring terminals to the wire and then solder them. Most of the time improper crimps are done and a poor one that is properly soldered to me would hold up better than just being properly crimped in the long run. With it properly soldered it also makes it harder to pull the wire out of the crimped terminal.

Since a battery can store a lot of energy, route the positive power cable so it would be hard to have it become shorted or pinched and if all else fails, add an ANL fuse right off of the battery positive post before it goes into the main power cable for short protection. On a lot of cars I've used 300A ANL fuses with 1/0 power and ground wires and trunk mounted batteries and not had problems.

Jim

 

Steel might not be as good a conductor as copper, but the difference is not relevant given the vastly greater cross-sectional area of your entire car compared to a puny cable (no matter how large).

However, it is correct that if you have high-resistance connections, you are hosed. Best bet for dependability over the long term is (1) good materials and craftsmanship when you put it together and (2) some level of redundancy (Battery to frame, frame to motor, body to motor, frame to body).

Many cars including Ferrari, Mercedes and Jaguar put the batteries at the far end of the car from the engine (with the battery connected to the frame), so obviously it can be done, and well.

 

Be careful with used airplane booster cable. Most of it spent a lot of it's life out in the sun laying on hot concrete. When the insulation starts to go they deteriorate real fast.