My 2004 E-350 15pass came with a second battery located under the sliding door where it is bolted in a box to the Frame rail. Does anyone know how that battery works? is it wired in parallel to the starting battery or does it run power to the van when the van is turned off?

Last week I had a dead starter battery that would not recover from re-charging and I had to buy a new one. I am trying to figure out if the second battery should have started the van, and if maybe I need to replace that battery as well.

someone told me that the second battery is a deep cycle type and runs the vans accessories after the van was shut off? Can someone point me in the right direction? HELP? HELP?

 

I've looked at the wiring diagrams because I had the same thing on my van last week. The second battery is in parallel with the main battery.

 

Thats really odd then? why didn't my second battery start the Van? I wonder if the solinoid shut down the current so the second battery would not be drained?

I wanted to get this figured out because I was thinking of adding some accessories to the back of the van and wire them directly to the second battery, but I'm not sure if thats a good idea if the second battery is in parallel with the main battery?

 

I dont know if it could be set up like an RV but on my E-350 there is a silver button on the dash that when you press and hold it it will start the van with the aux battery.

 

Solenoid? What solenoid? I didn't see anything like that on the wiring diagram. It just looks like it is always connected in parallel.

I assume that both batteries are dead. One may be salvagable, but it is usually better to replace both at once. If one battery is bad it can quickly drain the second one.

 

The factory option auxillery battery on the gas engines vans (diesels are different) are wired to provide isolated power to the trailer tow plug. They are not wired to assist the starting battery. With some modification, they could be.
The auxillery battery would be a good choice to power any accessories you add to your van that you don't want to draw down your start battery.
If you're not using your tow plug and have not connected any aftermarket loads to the second battery, then it's just there doing nothing.

 

Ok, so it sounds like they are wired parallel so that when the main battery has been charged while driving, the second battery is then charged. And the second battery is there to run power only to the trailer accessory plug, which I only use to tow a quad trailer.

If this is the case, I should not need to replace that aux battery just because my main starting battey has gone bad.

hopefully this information is correct for a 2004 E350. I am going to see if I can get an All Data print out on this and verify with the dealer before I start feeding power to the back of the van from the aux battery. But I think that the aux battery would be pefect to run a dvd player, spare power ports and play station for the kids in the back of the van!

 

That second battery sure is nice. I have a 2004 E350 and I swapped out the clutch fan with a big Flex-A-Lite electric puller, that's tapped into the aux battery at the power distribution box under the hood. All other aftermarket accessories I have are also powered off of this box.

 

I have not had a chance to open mine up yet to see what Ford has placed in that second battery box under the pass side door. Is it a deep cycle?

 

I'm not sure about deep-cycle, it looks just like the battery under the hood.

 

Down loaded information from a friends All Data software. Confirms that the second battery on gas engines is for the trailer plug. and that it is in fact a deep cycle battery. However it says that it supplies power to the trailer plug when the vehicle is running? So where do I tap in to get constant power ONLY from the second battery? At the battery post or the distribution box?

 

I have yet to hook up anything to mine as well other than from Factory I had them install the auxiliary power switches. From the back of those I assume I should be able to hook up auxiliary items. I have yet to pull the panel out as I don't want to break any tabs. I'm sure there are other videos on YouTube showing how to.

 

been looking for a good wiring diagram. Mind sharing?

 

Did you not notice this thread has been dormant for over 2 years now, that the member you quoted originally replied in Oct of 2006?

 

I'm wondering if anybody has an update on the topic of adding a house battery to their older E350 (mine is a 2001 Super Duty V10 Gas) to run aux items in the back of their van? My question: Can I replace the factory installed aux battery with a lithium battery to power the current things and a few new things? Or should i leave things the way they are and just add a 3rd battery (the lithium battery) to run a fridg and few other 12v things on occasion. It'll be charged with a DC/DC Charger when moving and solar panels when were camping. It's been a challenge finding out how its currently wired (with the two batteries it came with)how its wired and what they actually run. I see in this forum its was said the second battery is connected to the trailer plug. Yes I tow an RV trailer which has all its own power. To confirm, the factory aux battery is installed under the van below the side doors as described earlier in this forum. At some point mine was replaced with a normal motorcraft starter battery. The Lithium battery wont fit there so I've built a housing and mounted it in the back (passenger side). Thanks for any advice and information!!
Mark