We used our Cascade last in July. Just went to check on it. It's parked under my barn and hooked up to power. Everything is dead. No lights, power control panel, no power except micro wave when plugg...
I don't know if your fully drained batteries will come back to you or not...but before charging you may want to make sure they are fully watered (assuming these are batteries you can check). They may or may not survive, but if they are recharged when low on water then it almost guarantees they will be junk.