The biggest challenges faced by renewable energy users has been batteries. Charging them and getting them to last.
Most people never properly charge their batteries. They either under charge them or in rare occasions over charge them. Your sealed lead acid batteries are very sensitive to being charged. If you don't fully charge them daily you ruin them. If you completely discharge them you shorten the life of the battery. Over charging causes them to boil and you loose the electrolyte / acid in the battery. A dry battery is a dead battery. Your sealed battery (dry cell) has some form of electrolyte, it can be a gel or encased in some thing else. The lead plates need it to perform the chemical reaction that releases energy.

Q. When you charge your battery daily what is the maximum daily charge that you are required to put in your 12V battery?
A. Depends on the manufacturer But expect between 13.8 to 14.8 Volts.
Q. What is the float charge or cycle use charge for your 12 V battery?
A. 13.2 to 13.5 Volts. Also varies by battery type and manufacturer?
Q. Is your 12V battery charged or discharged at 12V?
A. Discharged. It has to be at 13 or higher.

I hope this helps you maintain and prolong the life of your battery. You can multiply by 2 for 24 and 4 for a 48V system.

Open Circuit Voltage vs. State of Charge Comparison*
% Open Circuit Voltage
Charge
Flooded Gel AGM
100 12.60 or higher 12.85 or higher 12.80 or higher
75 12.40 12.65 12.60
50 12.20 12.35 12.30
25 12.00 12.00 12.00
0 11.80 11.80 11.80