On my '87, factory batt cable tied both batteries together at one place then a single cable to starter and seperate grounds from block. Since I want to use military terminals for extra equipment, can I run two separate 0ga. wires and two separate grounds so I can pull off both evenly while using smaller cables? And if so, can I still tie the two together on the core support? Thirdly, I'm replacing the cable that feeds the truck with a new cable. In doing that, would I be further along by running of the batt or, could I run straight off the alternator since I'm also adding a heavier charge wire along side the stock one? These are just ideas I have. I've got a ton of 10ga wire and 15 ft. of 6 ga. I've already ran all new grounds under the hood. Thanks.

 

don't really follow what you want to do. how about a diagram to make it easier to visualize?

 

If I am following your post, you are saying with two 12-volt batteries connected in parallel can I run a positive and negative lead off each one to run auxiliary 12-volt equipment and the answer is yes.

I have never tapped the alternator for supply leads. Have always used the battery, so I can't answer that.

As Tom suggested, a little more detail about what you are doing would help give more definitive answers.

Steve

 

I looked at his signature, he has a diesel so that's where the two batteries are coming from. The factory ran a large + wire from the driver's side battery to the + of the pass side battery, and then went on to the starter. Usually the pass side + fitting is a special connector with the wire from the driver's side battery and the wire going to the starter all molded into the battery + post connector.

The two separate grounds are factory also, one from each battery going to each side of the engine block.

I am not sure what the problem is, that large cable the factory uses to tie the batteries together essentially makes them look like one large battery. You will never have enough load where that large factory cable could not let either battery share the load.

 

Agree completely. I was just responding to "will it work". Not sure what it is for either.

Steve

 

Never mind about tapping the alt. Directly, what I'm looking for has already been done just need to add a heavier cable. Just had to draw it out but here's what I'm looking at for starting instead unless I want to run an additional wire off the starter and I really don't want to. And its not in the drawing but maybe still tie the two together at the core support. If not, that's fine.



Just a quick sketch up.

 

doing it you way will work if you use large enough wire, but it will require a lot more wire than the stock setup.

 

That's fine. Factory used 2/0 awg. Wire to starter so I was going to run 0 ga. From both to make up the difference. This is only so I can add on equipment later. As far as the alt. Charging wire is concerned, for a 100 amp alt it seems kind of small. I was think of replacing it with either 8 or 6 ga. Cable with a inline fuse so when a heavy load hits the alt won't blow the little fuse link or melt the wire and can supply the needed current. And I'm also planning on doing a 3g upgrade so getting ready for that.

 

i never had any problems with the factory setup on my 88, and that has a snow plow and a 7 X 110 watt bulb emergency light bar up top. and that is with the stock alternator.

 

This truck is looking at additional lighting such as cab lights, whelen 9000 edge 8 strobe with alley lights and take downs, stereo, 1500 watt inverter, etc... I'm not worried about the alternator itself. Its that puny charge wire. This trucks under hood electrical was a mess and I'm just trying to get it all straight and up to specs. Thanks for all the help.

 

I would leave the large wiring the way it is, and I would certainly upgrade the charge wire from the alternator if you go to a 3g. As far as adding equipment, I don't think you will have any problem adding loads on either battery. Just pick one and add a aux fuse box under the hood somewhere to add your loads. Don't use the factory fuse box for any of those large loads you are planning. If you need something to turn on and off with the keyswitch you will have to add a relay or relays near the new aux fuse box to control the loads, and trigger the relays from the factory fuse box.

Ford did wire their trucks to handle the stock stuff, and that's pretty much it. If you add much of a load, you need to add your own wiring and avoid the factory harness.

 

What would be the "prop per" way to add a heavier charge wire then? Or is there a good tech. article on something like this?

 

I think I understand your goal but don't think what you have in mind is the best way to do it.

The factory cable is pretty darn awesome, you're not going to do anything better as far as starting goes then the factory cable, I see no point in messing with it.

All you need is a place to tap in, the factory starter solenoid/relay on the passenger fender is the ideal place for that. The only prerequisite being that the smaller built in cable going from the passenger side battery to the solenoid is large enough for your additions.

This same post on the fender is what Ford used to junction large power needs as well, it's ideal for your use. The battery, main vehicle power, alternator, and glow plug supply all come together on this one post. The glow plugs regularly draw 200 amps off the batteries, safe to say anything up to that load level is safe to attach there.

That post position can easily handle all the demands you mentioned here. Replace the stock wire from that post to the alternator with one larger and without the link and your all good. The biggest draw you've mentioned is the 1500W inverter, it will draw up to 125amps, that's just fine.

 

You can also just run a heavy 8 gauge or 6 gauge wire from the alternator to one of the clamp studs on the + connector on the battery. If you have a lot of threads sticking out, just slip it on and add another nut behind it.

 

this is what i did. i used a 2 gauge wire with soldered on lug from the driver side battery positive terminal to a circuit breaker panel mounted on the driver side inner fender and tagged all my relays off their dedicated breakers with low current trigger wires running into the cab to a switch panel.
with everything running i draw 110 amps off the driver side battery.
the snow plow is only a temporary drain, but when it is engaged the draw goes up to over 190 amps.
i have been using this setup without any problems at all for over 26 years.