Ford Dual Battery Setup - Page 4

dhally · 06-02-2011, 11:15 PM

I don't have the trailer wiring, but can test it at the batteries. It sounds like the system is designed to allow discharging the aux battery alone. If this is true, the factory relay and wiring must be protected against a surge of current when the batteries are reconnected?

Scalf77 · 06-03-2011, 02:02 PM

Surge current is would be in the spec of the relay. example the power relay used in the surepower 1315 separator is rated for 225 amps max with a inrush rating of 600 amps.

dhally · 06-03-2011, 03:41 PM

I did a little more research and it appears that the relay, wiring, and fuse are rated 40A (continuous). That should be more than adequate to run the house system. The only problem is the Group 65 battery is only about 54 A-hr. Maybe a Group 27 will fit in there...

Christopher Thwaites · 06-03-2011, 04:32 PM

It's the same battery as the main...type 27...at least mine is on my V10. I tried using it as a house battery but it wasn't sufficient to power my refer for very long. I added a third battery (100 amp AGM) just aft of the aux and wired it directly to my solar panel. So far I've never been able to run it down with the refer even when I've had several days of cloudy weather.

ANZAC · 06-04-2011, 12:29 AM

Learning about the aux position on the ignition key was a huge help to me! My trailer brake battery was low and I didn't want to idle the engine for hours to charge it, I was thinking of building a 7 pin socket with some alligator wires, now all I need to do is switch the ignition to aux.

Ultrasport12 · 06-08-2011, 01:32 AM

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.

dhally · 06-08-2011, 12:16 PM

Quote:

Originally Posted by Ultrasport12

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.

.....

Wow! that is exactly the information I was looking for. I just ordered a factory wiring diagram. I'm trying to see if I can use the aux battery, possibly with the addition of a second one.

Can you tell us if you're still using the factory aux relay system? Do you think it will charge the aux battery as fast as a voltage sensing battery separator?

Ultrasport12 · 06-08-2011, 12:44 PM

I am still using the stock relay for now and it has been no problems yet. For many years in both the Marine and RV worlds the debate has been Relays or Isolators, both have their own merits. Someday I may change the system a bit maybe a bigger/better relay and larger wires but for now it is working well with the extra battery.

FarmerFrederico · 06-10-2015, 09:40 PM

Dragging this back from the dead. I have the auxiliary battery on my V10 as well with a factory tow package.

I'm still new enough to understanding electronics that I'll have to re-read this thread a couple of times before I absorb it all and find out what is and isn't true from what people have said.

My first question is: Should/can I separate the auxiliary battery from the system and install an AGM battery in its place as my house battery? Or, should I leave it alone and get a second battery tray to sit behind it to be my house battery?

Thanks!

1der · 06-10-2015, 11:23 PM

Hi FF, Not sure how this will help but here goes:

I have a 2003 V10, it did NOT come with the aux battery on the frame. I did want a set of house batteries and spent a great deal of time figuring out how to get the most amp hours in the space along the passenger frame rail under the side doors.

What we ended up with was two AGM Group 31's at 105 aH each mounted on the frame rail laying on their side.

I was able to use a factory harness from a 2007+ diesel van that had both batteries mounted on the frame. This harness allowed me to tap into the battery cable terminal on the starter. I ran the cable back from this terminal back to a Blue Sea manual selector switch ( I do not like isolators/separators but one could be inserted if so desired) This switch resulted in one terminal connected to the engine bay battery via the cable from the starter, a second terminal connected to the two AGM's, and the third connected to the inverter. This way, by positioning of the switch, I can run the inverter from engine, house, both, or none. I can also, tie the system together for starting/charging, if needed, or I can tie the inverter to only the engine battery to allow the planned solar to charge the house batteries while they had no draw on them. Remember, this harness was the starting battery harness for a diesel engine, so handling a V10 should be no problem.

The whole set up turned out pretty slick and the battery tray made up of two factory battery boxes, cut and welded together sits up under the side body very nice and compactly. Plus I have a jumper post just aft of the battery box to allow charging of the house bank independently of the engine if desired, of would also have allowed quick connection of a portable solar charging system.

For your system, I would find a way to disconnect the frame battery from the engine and then replicate the system I set up. This provides for a 210aH house system using a couple of group 31 AGM's.