battery connections

[wallyH]

I've been having problems with my battery connections(I think). The boat's only a year and a half old and a few times last year and a couple times early this year I would occasionally run into a situation where I would get no power to the motor or any accessories. I eventually took the connections off the battery, sanded down all the connections and re-attached them and have not had that problem since. However, now I'm getting this problem where when I plug in the onboard charger the lights flash like it doesn't recognize the battery. Eventually it does and it seems to charge it fine. I know for a fact that the other day it was plugged in for 3 hours and still did not recognize either battery.

Does anyone have any suggestions for fixing this long term? The connections are posts with wing nuts. No evidence of corrosion.

Thanks,
Wally