Originally Posted by 
spudboy
				 
			I have a related question, if I may.
We have a standard 12v truck battery powered by a huge array of solar cells (ex-rooftop solar - overkill but 'free') through a 30A MPPT charger.
It is powering an Engel 39L fridge that is 25 years old.
In the morning, the voltage shown on the battery can be as low as 11.8 or 11.9v, but generally 12.0 or 12.1.  After an hour of sunlight, the voltage goes to 14.1 for an hour or two, then back to 13.4/13.5 for the rest of the day.
Is this damaging the battery to go down this low every day?  I know that fully charged is 12.7v, but not sure what the lower limit on a lead-acid battery is when this is happening on a daily basis.  
Is 11.anything volts doing damage?
Thanks - David