Originally Posted by J.R.
Voltage is not a true test of a battery. The best test is to place an electrical
load on the battery and check the results with a meter designed for this test. Another way is to check the condition of the fluids using a special hydrometer which can be found at many big box and auto parts stores.
What is fully charged? I don't give a darn about the last 8 AH of capacity. Fully charged for me is 98% or above.
Hydrometers only work with flooded batteries. Pretty much useless these days. I haven't used one in 40 years.
I don't use just voltage, although I monitor it to ensure my charge specs are not violated.
My charge controller is a three stage charger. While I'm sure a full charge is not in fact a full charge, it is accurate within 2% of fully charged. Batteries can take days to reach a full charge, which is irrelevant for my purposes as I use the sun to recharge it will never reach a true full charge unless remove all loads for several days.
I fully charged my batteries when I first got them and that will be it for a while. I don't intend to plug in any time soon.
I use a number of factors to monitor my charging--a battery monitor, which includes temperature status. Battery temperature will show how close it is to fully charged once in float mode. Temperature drops in the final stages of charging. Record keeping helps establish typical parameters which vary by battery.
panels were producing 29.8 Amps here at 2:29pm and only .5 amps are going into the batteries, the balance is going into running my energy hog fridge via the inverter. Now I am losing -0.7Amps as the inverter fan is kicking on and the sun can't meet the extra bit of demand. It is not a perfect system, but a very good one.