Introduction
The Airstream Interstate 24 comes from the factory with 400W worth of solar on the roof. 100W of that is dedicated to the Mercedes chassis battery for keeping charged and the remaining 300W is for the house batteries for the RV. With the van having a 12KWh battery, 300W does not go very far for recharging.
The E1 Package of the AirStream Interstate has an additional solar port on each side of the van for connecting external solar panels. While you don’t have direct access to the solar controller due to it being inside the Volta Power Distribution Hub, it is a Victron Energy MPPT 100 | 20-48V. That means its max input is 100VDC, 20A, its output max is 48VDC 20A. The 48VDC is a nominal voltage and the actual to charge the 48VDC battery system will be 58DVC. That gives a maximum wattage it can handle of 1160W, so with 300W on the roof, you can add an additional 860W worth of external solar.
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The 300W of solar installed on the roof is in parallel with the two side add on ports of the van. Their voltage is 75VDC. That means that any panels plugged in to the auxiliary ports, need to match that voltage as close as possible.
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This schematic shows how the ports on the sides of the van are parallel with the roof top panels.
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Airstream offers a 300W package that consists of three separate Merlin solar panels that are 100W each, these panels are 23.35VDC, giving 70.05VDC in series. The kit includes a cable that lets you plug these 3 panels in series with each other. Each panel has an Anderson Power Pole SB50 connector on it.
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The cable to interconnect the 3 panels has 3 of these connectors in series , with a Zamp connector to plug into the side of the van While not a perfect match, the approximate 70VDC they produce is close enough to work with the roof panels.
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These panels when combined with the factory roof mounted panels, give a theoretical max power of 600W but you will never get that efficient in practice. 422W was the max I got in testing but that was not during the peak summer months.
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With just some basic testing, I was able to around 422W of solar power without chasing the sun with the 3 panels on the ground. With repositioning on a good sunny day, I do think you could get in excess of 500W of solar power generation.
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While not enough to charge your batteries while you run your air conditioner, these extra panels can give you power for many of your appliances and add to the time you can boon dock running only on your coach batteries.
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To reassemble your device, follow these instructions in reverse order.
