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Old 01-13-2018, 10:50 AM   #1
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2009 v10 with factory 2nd battery / adding house batteries

After many hours of reading and researching, I have finally decided to post my question.

2009 v10 Cutaway Chassis
Supreme Box
Factory added 2nd frame rail battery

It appears I have the equipped 2nd battery isolator in the engine bay- 2nd Battery in box under passenger side of frame rail

I am wanting to add a bank of batteries ( house batteries ) AGM. Can I tie into the underframe rail 2nd battery directly? Would I need to add a second ACR or some kind of additional switch/relay for the house batteries to charge and disconnect when the vehicle is off?

Do I need to run an ACR standalone of the "factory ACR"? It would be nice to not have to make a run all the way into the engine bay.

Equally, if I tie directly into the frame battery will it matter if I am running AGM vs the I assume lead factory batteries
Some links I have been gathering

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Old 01-13-2018, 07:47 PM   #2
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I always thought the Dual Battery Systems were tied together not isolated by any means.
That's how it is done on my 7.3 PSD. So what I did was use the shorter length of 0 gauge from the frame battery to the house batteries with a blue Seas 7622 ACR.

2001 E350 PSD w/ a bunch of stuff.
And had three other E350s...
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Old 01-14-2018, 09:51 AM   #3
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Originally Posted by Bbasso View Post
I always thought the Dual Battery Systems were tied together not isolated by any means.
That's how it is done on my 7.3 PSD. So what I did was use the shorter length of 0 gauge from the frame battery to the house batteries with a blue Seas 7622 ACR.
Me too. I'm curious what's going on here.
Currently vanless. Weird.
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Old 01-14-2018, 10:09 AM   #4
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From what I have been reading the Diesel run both batteries as a "starter"

On the gas engines, the second battery was set up as a house battery or part of a towing package.

Speaking with a buddy who works on RVs he stated:

Pull out the second battery from the frame and hook-up a deep cycle AGM- as you can't tie in a 3rd and 4th to a lead acid starter battery.

By pulling out the second you are then charging the new batteries independently through the ACR. The house batteries need to be the "same" so they charge equally.

This sound like sound advise. But I am still digging

From one of the threads=
Ford includes two batteries with the diesel engine. They are wired parallel without any type of relay separating them.

Ford offers the "Heavy-Duty Auxiliary Battery" system with the gasoline engine. They are wired parallel through a relay as Mike has pointed out.

SMB installs a "house" battery(s) system that is separated/isolated (pre-07/04 built units) from the starting battery(s).

And another:

"Here is the deal on the optional FACTORY Aux battery on a gasoline powered van works, well at least my 2008 V-10. I just added a second aux battery with a tray I bought from e-bay. Here is what I found out.

The option Code is 634 $145 in 2008 you got ONE 78 AMP battery (main) and ONE 75 AMP battery.
The battery IS isolated from the main battery when the key is off.
The battery size is group 65 for BOTH of my Batteries.
The biggest problem of the batteries are how tall they can be and still fit in the box. 6 1/2 inches tall is it, unless you modify the box.
Aux batteries are available WITH and WITH OUT a trailer package.
Aux battery powers the trailer battery relay (if it has the FACTORY hitch wiring installed) when the key is on or off just like it does if you don't have an AUX battery but if the trailer drains the battery with the AUX battery the van will still start.
The relay for the Aux battery is mounted under the main battery.
The part number is F8UB-14088-AA
There is a diode in the hot in run circuit, it is mounted in the (as Ford calls it) BJB or battery junction box next to Fuse F5.
This wire on my van is White and Black 14 or 16 gauge and hooks to the small/energizer terminal of the relay.
One of the large terminals on the relay is another Black and White wire. This one is 8 or 10 gauge and hooks to a 60 AMP Fuse F20 in the BJB. This wire is Hot all the time.
The other large terminal has the feed wire to the Aux battery and a Red/Yellow wire that
feeds the trailer relays via BJB Fuse F24 20 AMPS and Fuse F8 40 AMPS.
(note without an Aux battery these two large wires have a jumper in them in at connector C145)

I hope that helps any of you who have wondered how this all works. I spent many hours with the factory Ford wiring book and a volt meter making sure this is how it works before adding my Second Aux battery to my system. The manual makes it look to me like the relay should have four terminals but mine only has three.

Oh and the reason for disconnecting the Aux battery ground (at the frame connection) is because it DOES power the trailer relays all the time even if the other battery is disconnected completely, plus one terminal of the relay is still hot."
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Old 01-16-2018, 09:26 AM   #5
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Your buddy that works on RV's is correct. Unless I had a future use planned for that battery, I would just disconnect and remove.

There are lots of threads here on choosing a ACR , etc.

2004 E350 EB V10 E/PH 2WD
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