Regarding battery corrosion, it can be cleaned off with a baking soda and water mixture which neutralizes the acid (corrosion)......but.....DO NOT get any baking soda mix into your batteries. Ideally you should remove the batteries and wash them off with water and use neutralizing solution on the battery tray and battery straps. You can soak the straps in a small plastic tray and then rinse and dry. While the batteries are out, if you can pop the maintenance caps off (if equipped) make sure water levels are up above the plate tops and use only distilled water to top them up. Also do not get battery acid or corrosion on your clothes or it will look like moths have been visiting your closet.... in a few days; (skin and eye protection is a must). Also clean the battery posts with a post cleaner you can buy cheap at any automotive supplier. Clean all the battery cable terminal ends too.
By the way you may find that fairly soon after the car battery charger was applied to the coach batteries (while still in and connected to the coach)....you may be able to engage the use/store latching relay (should hear the clunk when it operates or releases) and then continue charging with the coach converter plugged into shore power. You need a cheap multimeter to ensure that the coach batteries are actually charging (13.1vdc or higher). If voltage is less than that when charging you have a problem somewhere in the coach charging circuit (latching relay open; 50 Amp resettable breaker open; 100 amp fuse near batteries open where equipped etc).
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