If your van has a "isolator" instead of "separator" then hitting the charge button will do nothing for your starting batteries. Sportsmobile did not start using separators until mid 2004.
-greg
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-greg
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"Goldilocks" 2020 Ford Transit High Roof Extended 3.5 EcoBoost AWD Homebuilt
Unfortunately as Greg points out that's the way they work. Isolators are made so you can't kill the starting batteries when the engine is shut down and you use up the house battery reserves. Think of Isolators as a one way valve. Most inverters are tied directly to the house battery system. So are most solar setups. The isolator will allow the alternator to charge the house battery but blocks backward current flow from the inverter to the starting system.
SMB did make a kit to replace the isolators with a separator but that stuff may be long gone. If you have an isolator chances it will be on the firewall.
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2006 Ford 6.0PSD EB-50/E-PH SMB 4X4 Rock Crawler Trailer