On 18 Apr 2018 17:50:12 GMT, KenK wrote:

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
Try replacing the clamps with a more permanent connection, since you
use it as a permanently connected device.