OK , what im trying to do is determine what is a good cutoff point for a 12v battery (automotive) . Im going to use the Arduino to shut off Relays so nothing else will draw current untill the system is charged enough from the solar panels again. Many web sites are kinda vague.
They tell me a dead battery is about 10.5v .Thats not very helpful, the battery will take damage at that kinda discharge.
So anyway 
thoughts/suggestions would be greatly appreciated
12.8 is 100%, id say 12.2 is pretty low, 11.8 you should kill the power I think that's 10-15% left and any lower would be bad, this is assuming a deep cycle battery, if its a regular auto battery(designed for more cranking amps) you may not wanna go below 12.2
Its a marine battery (hybrid) so probably around 12.2v/ 12.3v ish would be a safe cutoff, to give a nice longevity of the battery. Sound about right ? And what you think 12.6/12.7v a good place to come back on ?
When are you going to measure the voltage? If you measure it while its charging it'll be higher momentarily, as high as 14 volts then drop to 13 in time after its done charging, so depending on what kind of load it is you may not want to turn on until its full, or maybe it doesn't matter idk, but if its charging it'll probably say 12.7 and if it were to be disconnected it would drop lower which kinda gives a false sense of it being done
Yeah can't hurt to shut off earlier, although that kind of battery can probably handle it,
Yea i'm just mostly wanting it for safty of the battery,Rather shut off the load , than discharge the battery to low, thanks