QUESTION SOLAR PANEL AND POWER

[brian22]

how to know if my backup storage is already in full charge lets say if i have this batteries
and i use this panel 80W.

 

[Externet]

You have to ask the battery manufacturer for the full charge voltage of such battery after what time has ceased to receive charge, if you don't want to get into electrolyte measurement.
Example : a 12V battery being charged by a 13.8 V source measures that: 13.8V
Ceasing charging, after 1 hour disconnected, it should show 12.68V, for 100% charged state or the figure told by the manufacturer.
The solar panel does not have much to do in your question as depends on how long, how sunny, how discharged it was when charging started.