I did a quick search, but couldn't find anything on this, but will Ford be allowing for dual alternators on the Transit? The reason is that the second alternator could feed a set of house batteries, which would feed a decent inverter. If this is possible, it would be nice for running electrical appliances like a microwave in an upfitted van.
You do not need two alternators to run a microwave in a conversion.
Attached is my electrical diagram for the Transit. It is very similar to what I had in the sold 08 Sprinter. The Sprinter house electrical was completely separate from the Sprinter vehicle electrical. The house 12 volt system was not even grounded to the chassis. If I wanted I could have removed the house 12 volt system and without changing any wiring it would have worked in the driveway.
What I did in the Sprinter was not the normal RV setup that used the vehicle 12 volt alternator to charge the house battery. There are numerous things wrong with the "normal" RV setup:
1. You do not charge the house battery with a quality 3 stage (bulk/absorb/float) charger.
2. The alternator charge profile is not matched to your house battery.
3. You are charging two different size batteries at the same time.
4. You may be charging two different types of batteries at the same time (Flooded and AGM).
5. You would be charging two different age batteries.
6. You probably would be charging two different brand batteries with different charging requirements.
7. You could overload the alternator.
The solution that worked well for me was to have two inverters. A "vehicle" inverter that was powered by the Sprinter and a "house" inverter that was powered by the house battery. The vehicle inverter was a 600 watt pure sine inverter to provide 120 volt power while driving. That 120 volt power was "shore" power. I also had a real shore power cord. A 3 position battery selector switch (Blue Sea # 9009) could select the vehicle 120 volt power or real shore power or off. The 120 volt power then went to a Magnum MMS1012 1000 watt inverter/charger/transfer switch. The Magnum has a programmable charger where you tell the charger the battery size and type. It then provides the correct charge profile for that particular battery.
The rest of the electrical system included a 255 amp-hr Lifeline AGM 8D battery, the Magnum RC-50 controller and the Magnum BMK battery monitor. I would set the remote to read SOC (state of charge) to keep me informed about the charge level in the battery. The solar system was additional. Solar panel was a 205 watt panel and the solar controller was a Morningstar Sunsaver 15 amp controller. Solar controller was also a smart charger that has bulk/absorb/float matched to the battery type. I went for a year without using either shore power or "shore" power from the second inverter. I did cheat by turning on the vehicle inverter while driving so that my largest load (4 amp DC refrigerator) ran on 120 volt power instead of the house 12 volt power.
The 1000 watt house inverter would run a cheap ($50) K-Mart 600 watt Proctor-Silex microwave. Microwave is ideal because it has old fashioned mechanical dials without a clock or pushbuttons. When not running it would not use any power. Besides I soon learned not to have the Magnum inverter on unless I needed 120 volt power. It used 7% of my battery capacity just being on overnight without any load. They use a lot of power just being on. The microwave used about 1% ot the battery capacity for every two minutes of use.
Transit system will have a few upgrades. Vehicle inverter size will be increased from 600 watts to 1000 watts. I will use the vehicle inverter while driving to charge the house battery or
heat shower water electrically or
power a 750 watt electric baseboard heater in rear of van. The larger inverter will allow me to charge at the full 50 amps allowed by Magnum, reduce the 5 gallon water heating time from 45 minutes to 30 minutes and I can add the baseboard heater. The solar panel will go from the 205 watt panel to a 300 watt panel. Same physical size. About $75 more that the going $1/watt cost of solar panels. Should be worth the extra cost on grey days.
This design worked very well for my application. I did buy the HD alternator and the dual AGM batteries in my Transit. I also bought remote start that will allow me to heat up van in morning without getting out of the sleeping bag. I let the van interior get cold at night and I stay warm with a 12 volt heating pad under the zero degree sleeping bag. I also wear a balaclava to keep my head warm. No heater and very little refrigerator run time makes for a quiet nights sleep. Also very stealth.