[ecomodded]

10.5 volts is a flat battery 8 volts is a dead dead battery.
It may never be the same.
It may mostly bounce back but like Daox said its life has been shortened.
I will suggest solar panels for the rear and front dash combined with 2 deep cycle batteries. Also carry a battery charger.

I am using my alternator, but i use it less, with a 15 watt solar panel on the dash and a deep cycle battery under the hood.
It keeps my battery at 14 volts, whilst sitting and adds up to a amp of power while driving.

I may put my other 15 watt panel in the rear window, then it could be making up to a 2 amp boost while driving.