Ok, I'm done trying to understand the theory. I've read every post in this forum, had you and MarcoPolo and BBQ and everyone explain things to me and I really wanted to figure this out and do it myself, but I still don't get it. So I'm just going to ask:
I have a 230 amp alternator and 2 x 12v 100ah AGM batteries (ambulance prep package) on the Transit chassis; then I have 2 x 12v 105AH wet cell batteries for the house.
I want to run 2 x 15v computers for several hours a day and I want to run a 120AC 900w (1100 watt pull) microwave for 10 minutes (about 5 minutes at a time).
What is the best way to go about it?
:bow:
Unfortunately, there is likely not an answer we can just give you, as the system you have right now is not really conducive to what you want to do without some modifications.
If I understand the description correctly, the ambulance prep gave the big alternator and two AGM batteries that are basically in place of the van starting battery? If so, you wouldn't want to run stuff off them for very long because if you kill them, you wouldn't be able to start the van.
You also have a mix of wet and AGM batteries, so even if they were all available to the coach, they would need to be used and charged separately due to the mismatch of chemistries and style.
To know if you can run the computer, it would be necessary to measure the amount of 12 volt power to the inverter is needed to run it, which could then give an accurate time and affect on the batteries.
Is there a wiring diagram or schematic that the manufacturer would be willing to give you for your van, so we could tell better what you have and what would be the best way to proceed? You might also need the Ford wiring diagram for the ambulance package, which is likely available in the upfitters information pack from Ford.
My guess is that you would need a good inverter charger, like a Magnum MS2000, which improve both your inverting and charging capacity. Getting all the batteries tied together, and not starting the van with them, would be great if you can get a single smaller battery to start the van mounted somewhere (it may already have on as part of the ambulance package, too). You would need to change the wet cells to AGM to do all of the above so the batteries match and charge and discharge together well.
My guess is also that it will be a pretty big job to do, as there would be wiring changes and big cables to be installed in a finished van.
In reality, you would be winding up with a setup similar to what Avanti, Boxster, and I have in our vans, so probably a similar amount of work.
Are you in an area where you are near any of the members here that might be able to look at your setup and collect some information, maybe pix, for you to provide? That would be really nice if you are that lucky. Getting a hold of the manufacturer to check on wiring diagrams would also be a good place to start. The hardest part of all this is always to get it all correct the first time, so the more information that is available up front the better.
Sorry there isn't a basic answer for you, but you have just too many unknowns at this time to do much more than speculate. I do think that 400ah of batteries will be enough for you, depending on how many days you need without charging them, as long as you can come up with a separate battery to start the van.
