New Battery Cables - Why Wouldn't This Work?
 

I need to make new battery cables for my 91 SAE Bronco diesel conversion. It's got a 1988 7.3 IDI in it. Ford + battery cables go from the driver's side over to the passenger side, then down to the starter with one extra leg going to the solenoid on the fender (which in this installation is acting as a relay only since the starter has it's own solenoid). So wouldn't it be better to run 2 seperate + cables from each battery and join at the starter? Can't I still run the leg to the relay off the passenger batt + since it is just running the glow plugs and all other power to the truck? This way, the run from the passenger side battery is not carrying all the juice from both batteries to the starter. I've got plenty of welding cable - why would this not be a better setup than what Ford intended? What am I not thinking of? Opinions wanted.

I'm no electrical engineer but it seems that Ford probably knows what works and it has proven itself for over 20 years. I don't think that current is being drawn through the pass. battery as much as they are together acting as a large storage of amps. Surely power is drawn from the drivers side battery just as much as from the pass. battery minus the losses from resistance.

Another issue I see is charging the batteries in the setup you described. Isolating the driver battery to the starter alone means it is out of the charging "loop".

Not sure if the right terminal is available for the joined wires between batteries but maybe you could use a battery switch for boats or something similar to run the batteries together. Just a thought. Good luck!

I think you misunderstand - I am not isolating the driver's side battery at all. They will both be connected to the starter AT THE STARTER instead of at the passenger side battery. Ford's solution saves them money on every truck because it takes quite a bit less cable and they are using #2 so it is expensive.

So you just want to add another positive cable that runs from the drivers battery to the starter on top of what the factory did? Go for it, it can't hurt anything. I doubt it will make any noticeable difference but it is your truck, cable, and time. I agree that manufacturers will cut corners to save money but I think that if this was one of those cases it would have been a common problem on these trucks well before now. It probably is a better setup in terms of power to the starter, but what will you net from this setup? It may be better if your batteries die down to the point that every last ounce of energy could make the difference.

I added a schematic to help better understand. Keep in mind I have to replace all the cables regardless - they were junk.

http://jastrauss.fastmail.fm/batt_cables.jpg

I don't see any reason why it wouldn't work if you want to do it.

You're correct, it's essentially the same arrangement. I was assuming that there was no solenoid on the starter itself.:o I put my foot on my mouth. After being able to look at my truck and realize my mistake, it looks like it should work fine. The charge going back will just have more resistance, but since they are all new cables that is probably of little significance.

i see no reason to do it this way. it will cost more to do that than to just replace cable with what ford designed.
from silver state ford is $88
https://www.silverstatefordparts.com...350-parts.html

Uh, no. I got 25 ft of welding cable for $50 delivered and all the terminal ends are free to me. So for $50 I can make all the positive and negative cables. What you are quoting is for the positive cables only.

what amperage is your welding cable good for?
i think those starter motors draw something like 300-500 amps(not sure)

i figure that you will have a voltage drop for the glow plugs and everything that gets power from the passenger side batt, but i doubt that it will be noticeable

What size cable could you get for that price? Either it was underpriced or is really small. I am running 4/0 from the driver's side battery to the starter, and a 2/0 between the batteries. Both grounds are stock (look like 3/0).

It's 2/0 - Made in USA.

I used 2/0 when I did mine but ditched the second battery and bought a Odessey 2150 battery. Still works like a champ 6 years later...



Javier

I used to have a 1989 F250 diesel I ran with only 1 battery, it was an Optima Red Top. It worked fine here in Texas.

considering the fact that ford used 2/0 wire to handle the load of one battery (between batteries) and 4/0 to carry the load from both batteries (to starter), it seems to me that for the OP to use only his existing cable in the factory routing would be inferior to doing it as he intended. with the original routing, the larger wire is required to carry the full load to the starter, so he would either need to buy a section of 4/0 wire for that section, or wire it as he had in mind.