I have been researching how to install a big 12V - 240V inverter in my van. Not long ago
@WoodsWeapon mentioned a guy on VitalMX who had such a setup. I managed to get a hold of him, but he referred me to his more electrically skilled friend, who actually came up with this installation recipe. Here is the recipe:
RECIPE #1
1) Buy and install a dual alternator kit. Nations Starter & Alternator offers
Multiple Alternator Kits The prices range from $650 for popular trucks with just one upgraded alternator to almost $2K for dual upgraded alternators and a regulator for more exotic Sprinter and ProMaster vans. You may want to consider a triple or a quad alternator kit too, hehe.
2) Buy and install a 400W 12V - 240V pure sine wave inverter. Those cost about $1K. This one is a good option:
4000 Watt Pure Sine Inverter Charger - 12 Vdc to 120/240 Vac , and so probably this one:
Discount China 4000W Peak 12000W DC24V Pure Sine Wave Inverter With Charger 65AMP LCD Screen - www.sungoldpower.com . I recommend you check their Amazon ratings as well. I like the first one because, apparently, it can provide 110V and 240V simultaneously.
3) Install two deep-cycle marine batteries. Four batteries is recommended in order to charge a Redshift from zero. I am not sure about their required capacity, but I imagine the price can be around $1K or so.
4) A knowledgeable guy recommended a high idle kit for the van/truck. It keeps the RPM above the default 700-800 rpm. Apparently the regular low idle still discharges the deep cycle batteries before the Redshift is fully charged. The high idle kit can bump it up to about 1800-2000 rpm while charging.
That's it.