I keep a deep discharge RV battery on a Battery Tender charger all the time in my home for power outage light and fan. I've been doing this for decades, going through two or three batteries and chargers.
At present I am having an annoying problem. The charger red light comes on - meaning no connection to the battery I assume. If I press on the battery clamps so they dig into the battery terminal for a good connection the green charger light blinks, and soon glows steadily, indicating it is charging and operating correctly. But soon the same situation reoccurs. I tried a battery terminal wire brush and the terminals are now shiny. I cleaned off the charger clamps as best as I could. Problem continues.
Appears to be a charger clamp connection problem or, somehow, a charger problem.
Suggestions?
TIA