Way Elite solar charger/controller malfunction

Personally, I think the chassis battery is fine. Takes and holds a charge fine. It just went dead sitting 2 weeks in storage. I think Mercedes nature of the beast with all the electronics. It was enough charge to start it but barely. I've had similar experiences with an e350 and c300 I previously owned, and a bmw when they sit for 2 weeks. Heck, my 37 year old jeep does it too.