I agree 100% that Airstream needs to improve the battery capacity on the Interstate. I've posted it here before that Airstream is behind their market competitors (based on price) , like Roadtrek and Advanced RV, who now offer large lithium batteries that solve the battery limit.
To solve this issue myself I'm now adding four Lifeline GPL-4CT, 6volt batteries in series pairs. This will give me a total of 440 AH of capacity. I'm also upgrading to a Magnum MS-2000 inverter/charger that give me 2000 watts of 120v AC power to run the microwave. Here are a few photos of my new battery racks under construction in my shop.
I will mount a pair under each side of the van just behind the rear wheels. Like my solar upgrade this is turning into a big project that I'm half way through and wondering why I ever started.
I chose to stay with AGM batteries after doing a lot of research on lithium batteries. I like the advantages of lithium, but they require a total system redesign for proper charging and protection. Lithiums also require special considerations for operation in freezing temps that we get here in Maryland.
- - Mike
2013 Lounge EXT on 2012 Sprinter