No flame, but this flies in the face of all electrical circuit design principles I know of.

1. The electricity coming out of the alternator and / or the battery does not "go" to any particular area of the electrical system 1st, 2nd, 3rd, etc. The majority of the circuits are wired in parallel - in other words, they all receive voltage from the same sources at the same time.

2. If you do relocate a battery, the most critical aspect of the relocation is that you use wire of heavy enough gauge to offset the additional resistance caused by the increased length. This includes the grounds too !!

3. As long as the cables connecting the battery to the alternator and ground are of proper size, there will be ZERO difference in how the electrical system functions in the truck.

4. When voltage fluctuations occur in ANY direct current circuit (DC) it is almost always due to improper cable selection for the physical circuit length and amperage load used by the circuit, or poor connections in the power supply circuits, or too much current draw for the power supply.

5. The amperage draw of a DC circuit directly affects how much voltage drop a cable presents to the circuit. For example:

A 20' length of #1 AWG stranded copper cable will cause a .1 VDC drop while a 40 amp load is drawn through it.

Draw 120 amps of current through that same exact cable (our alternator's max output) and the voltage drop will be .3 VDC.

If people are seeing voltage drops any place on the circuit (after a battery relocation), several things could be wrong. I'll place them in order of likelihood:

1. Battery cables sized too small for the application.

2. Poor grounds between the truck frame, body, engine, alternator, etc.

3. Poor contact between the new cables and any connectors, splices, etc. used to connect them into the truck's electrical system. Poor connections to the frame, body, etc, are likely as well.

In short, it is not black magic, rocket science, etc. to relocate the battery - I know because I relocated mine long ago with ZERO issues.

I hope this helps to clear things up just a little bit...

 

First you must walk on rice paper and not leave mark.

 

If you accomplished the above ^ then:

Boost a spark or similar device on INPUT voltage line to MAF that will regulate INPUT voltage into MAF and also clean up dirty ac/dc signal.

 

I think a FAST or BigStuff3 will do the same thing

 

Why waste time explaining design principles and working logically through the issue when you can just lob a statement out there?

I can only speak for myself, but assuming that the devices are in fact in parallel, it certainly does! I am going to bust out the wiring diagram and check it out.

One last question: what wire gauge did you use? I used 1 ga. all the way, including to a master disconnect on the roll pan. I soldered on the ends using the fill-it-up-with-solder-and-shove-the-wire-in method.

 

nice cable work Tim
wish I could put into words properly what I know my hands can do
mitch

 

The battery, the alternator, and any device which runs on battery power is in parallel. That's true, as far as it goes. However, long/undersized cables or poor connections act like resistors, drawing down the voltage before it gets to the device wanting power. If you have moved the battery to the rear, like I did, you can have low voltage to the PCM, fuel pumps, etc. for the reasons above. You can also have low voltage and charging/starting problems because the alternator "sees" the battery as fully charged when it's not. It sees the voltage drop and battery voltage as one, so it stops charging early. Use 0 gauge or, at worst, 1 gauge, fine strand cable, solder all connections possible, clean the grounds and see if that cures the problem. If you have a good digital voltmeter you can check the battery voltage and then the voltage at different points of the system to see if there is significant loss in the cabling.

 

Wow. I thought I DID explain myself... Tough audience !!!

Let me try again:

If you relocate the battery, the only difference you will introduce into the electrical circuit will be completely determined by 2 factors:

1. What size cable you select.

2. The quality of the connections between those cables and their end points.

Quicksilver is absolutely correct: If the cable you run is of insufficient size, it will "look" like the battery is at a different voltage than it really is. When your entire circuit only has 12-14 VDC to work with, a little drop can mean big problems.

Part 2 of this puzzle is regarding the current draw of the entire system. As I stated earlier, as you increase the current load on the cable, it's voltage drop increases as well. The way to properly test the problem truck would be to turn on EVERY electrical device you can to put the maximum load on the alternator. If the load is greater than the alternator can supply, the voltage will begin to sag. This is commonly observed by people with high power amplifiers - when the big bass strike occurs, the headlights will dim. If you were to measure the voltage at the battery when that occured, you would see it was lower than "normal".

Get a 9 volt battery. Measure it with a DVM. It will read 9.?? volts if it is good. Connect a 4 Ohm resistor across it and measure the voltage again. It will be much lower than 9.?? volts. Why ? The current load is too great so the voltage sags. Remove the resistor and, providing the load wasn't on the battery too long, it will read 9.?? volts again.

That is why a car battery can be completely "dead" but if you measure it without a load, it might read 12.?? volts. When they die, they lose the ability to generate current.

Please do. Keep in mind that you are looking for the states of the various relays, solenoids, etc. while the truck is running. Obviously, the circuit characteristics change when the starter is engaged, but for the purposes of my earlier explanation I assumed the truck is running, perhaps on a dyno.

Nice cable job, Tim. The first rule when making a good electrical connection is to make sure the conductors are clean. You obviously did that or the solder would not have flowed properly.

I would caution you on one thing: The second rule when making a good electrical connection is to make sure the connection is a mechanically sound one (crimped, in this case). Copper and solder have very little resistance to vibration and flexing - copper will fatigue and break, solder will fracture. If at some time you find the need to re-work your connections, crimp them first and then solder them. In lieu of that, be sure that the cable is well supported mechanically so as to not put physical strain on the soldered connections.

I used 0 gauge, fine strand welding cable for my relocation. Welding cable is good because:

1. It is usually cheaper than the cable you can get at an automotive supply house.

2. Welding, by nature, is a low voltage / high current application, just like a vehicle.

3. The insulation on the cable is tough because the cables are expected to be drug around work sites, across rough concrete floors, etc.

As far as the original post regarding the electrical problem, I still think there is an issue with the connections / grounds on the truck. Or, something is wired incorrectly or the cable selected is insufficient for the load. I am not sure about the alternator's capability of handling 2 batteries - I thought that vehicles with 2 batteries typically had very high output alternators...

I apologize if the first post seemed smart-@ssed or something. I really did not intend it to come across that way.

 

Sorry. I was being sarcastic and attempting to compare your well-reasoned and well-written post with some of the previous replies. YOUR post was beautiful.

But the follow-up is still most appreciated, and will hopefully be appreciated for generations to come when they perform searches!