Battery cables

Ford did change this on the newer trucks. My 03 Excursion has the engine electrical fed from the passenger side battery. The cabin electrical is fed from the drivers side battery. There’s a large positive cable between the two batteries, but there’s a lead that bolts to the drivers side battery,that goes to the cabin. You can unhook it and everything inside goes dead.

Selahdoor said:

Starter is 'technically' closer to the passenger side battery, right?

I believe the GPs draw from there, as well, right?

How about moving the GP system to draw more from the driver's side battery?

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On that year E350 you got 2 passenger side batteries. One on the frame, one under the hood. Both new batteries went inside, and the old cables for the underhood battery ended up as a high-amperage junction point... where the GP system (now manual) got fed from.

u2slow said:

On that year E350 you got 2 passenger side batteries. One on the frame, one under the hood. Both new batteries went inside, and the old cables for the underhood battery ended up as a high-amperage junction point... where the GP system (now manual) got fed from.

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Thank you.

Speaking strictly in terms of my own truck...

I will be putting headlight relays in. I'll power those from the driver's side battery.

Also going to use Wes' suggestion about the switching wire for the GPs. (Moving that to be fed from the high idle circuit.) While I am doing that, and am in there, anyway, I think I'll change the feed wire that actually brings the battery power to the GPs... Over to the driver's side battery as well.

To see if you have a problem when cranking just put neg voltmeter lead on driver side NEG batt post, not terminal, and pos voltmeter lead on pass side NEG batt post and have helper crank 5 seconds or so. Will read 0 if not cranking (and nothing turned on), unless something very wrong, and should be less than 0.05v cranking (way less is better). Digital vm not very useful for this, use old style moving pointer like Simpson 260. Switch and do both pos posts which will show more voltage due to cable setup. Voltage divided by lead resistance and connections equals current imbalance while cranking. For more accurate test, make both neg leads same length and clean terminals. This is one of the battery killers in our trucks. I will try this after finishing reinstalling second battery (now in Bertha).

Back in my army days...all the vehicles I ever worked on had batteries in parallel. Everything from track vehicles to the hmmwv. Saw someone make the mistake of connecting 4 batteries in parallel the wrong way. Made for a minor explosion and lots of sparks. Even those weren’t balanced to efficiency though. Always saw the pos and neg lead start on the same battery. If you can balance the load and charge in your truck by switching which battery the pos and neg start on, it should have a benefit. Your only real limitation is cost and routing of the cables I think.

If we were not having cranking/battery problems no change needed. Trying to come up with minimum change/cost for max benefit now. Changing all batt lugs to bolt on style, 7 places, stops need for new cable when stock lug rots off. Moving pass side neg batt cable to drivers bat provides current from now correct location. Then only need cable from drivrs batt neg to pass batt neg, easy since now bolt on lugs. So get 7 feet 2/0 welding cable yard sale, 4 military style bolted batt terminals, 7 crimp on plated lugs sized to match cables (or make from tinned copper tubing), a cable cutter, and rent a hydraulic crimper and go for it. About $30 + scavenged cable per truck.

Terms for 2.5 trucks $39 https://www.ebay.com/itm/Military-B...697042?hash=item2cbd7dc412:g:jiUAAOSwKJhbQRAY

Cutter $20 https://www.harborfreight.com/10-in-cable-cutters-63827.html

If we're going to get really fussy about load balancing, then no loads should come directly off a battery.

The batteries should be wired with equal-length cables to a common distribution point where the loads and charging circuit are connected.

The crappy part is the mfr has already decided where the batts are going to be, and cut all the corners possible as far as wiring them.

Is the Drivers side battery you want to jump if you have dead batteries? Or passenger side ?

Passenger's side. That's the shortest route for the power to take to get to the starter and the rest of the truck.

Well I know I've always believed in lots of good clean grounds everywhere to anything I could run extra ground wires to!
But after reading thru all this it do make sense. Things I never really thought about!

@PROFG point of data. My batteries from intl dealer are 5 1/2 years old. They're getting tired. I pulled the labels off them and although they're "maint free" they have individual caps.

The passenger battery's water level in each cell was around 1/2” - 1" lower than the drivers side battery. Could be I've got a bad connection to the drivers battery. Could be that it's the way the cables are ran.

PROFG said:

This, might, slightly improve charging only with very little cranking effect. Highest load is cranking, that should be balanced with pos and neg cables to STARTER, with smaller cables to frame ground and solenoid/alternator. Almost the only designs like our trucks are done by manufacturers saving a few cents per vehicle. Check out how the rest of the world connects parallel batteries. For a hoot, check out 3 or more in parallel.
https://www.impactbattery.com/blog/tutorials/how-to-charge-marine-and-rv-batteries-in-parallel/

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We live off grid, powered by approximately 1000 Watts of 12 volt solar panels and our power bank consists of 4 6 volt golf cart batteries two strings of two, essentially making two 12 volt batteries. Let me tell you that in the off grid world where you are living off battery power and if you have a large bank replacing them gets expensive. Folks pay attention to using the proper gauge and cable length so that the bank is balanced...

u2slow said:

If we're going to get really fussy about load balancing, then no loads should come directly off a battery.

The batteries should be wired with equal-length cables to a common distribution point where the loads and charging circuit are connected.

The crappy part is the mfr has already decided where the batts are going to be, and cut all the corners possible as far as wiring them.

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Loads off a battery BANK, if balanced, much better than off A battery of a bank. Common distribution point ok for rest of small loads but starter current should not have to flow thru frame and engine.