stock battery charging configuration

[4cruzer]

Hi folks,
I've been looking around the web for an answer to this, and my search techniques are failing. I can't seem to get a straight answer:
In a 7.3L PSD van (1997), are the two stock batteries always connected, or is there a solenoid/ isolator in there somewhere? If there is a separator, on what parameters does it operate?

My house battery is going in, and I planned to connect it to the system via the second (framerail mounted) battery... Any reason why I shouldn't?
Thanks in advance for the help. Some of this electrical stuff confuses me deeply.

Cheers
GB

[carringb]

On the diesels, (and 2012 gassers) both batteries are always in parallel. No isolator or other switch present.

The gas vans (until 2012) with an aux battery have an isolator that will charge the aux battery once the starting battery has a suitable charge. If you can find an isolator that will also do this, I think it's a good idea.

[j.whitbread]

FWIW - I have the factory aux battery under the foot well on my 2007 E350 V10. I have a wheelchair lift and power driver's seat base connected directly to it. I had to replace it recently because the lift stopped working, the seat moved really slow. But the van still started fine.

The battery under the hood is the starting battery. In stock configuration, you can run down the aux battery and still start the van.

[carringb]

Originally Posted by j.whitbread

FWIW - I have the factory aux battery under the foot well on my 2007 E350 V10. I have a wheelchair lift and power driver's seat base connected directly to it. I had to replace it recently because the lift stopped working, the seat moved really slow. But the van still started fine.

The battery under the hood is the starting battery. In stock configuration, you can run down the aux battery and still start the van.

But that's true for the gassers only. Diesel = always connected.

[4cruzer]

Thanks to you both for the input; makes sense to me.

Time to get batteries tested.

Thanks again!
GB