"maintenance free" is a bad joke in hot areas
batteries need water and "maintenance free" ones are not sealed
as a cell ages it gets higher resistance to charge current that = more heat
and more heat = lost water and lost water = dead battery
even the newer teck gel or mat type will have water lost over time
from the gel or mat by heat of charge current
the hope is it should take a bit longer
the other problem is sulfation
''16.2. Heavy Sulfation
Replace the electrolyte with DISTILLED water, let stand for one hour, apply a constant current at four amps at 13.8 VDC until there is no additional rise in specific gravity, remove the electrolyte, wash the sediment out, replace with fresh electrolyte, and recharge. If the specific gravity exceeds 1.300, then remove the old electrolyte, wash the sediment out, and start over with distilled water. You might have to increase the voltage in order to break down the hard lead sulfate crystals. If the battery gets above 110o F (43.3o C) then stop charging and allow the battery to cool down before continuing. Cycle (discharge to 50% and recharge) the battery a couple of times and test capacity. The sulfate crystals are more soluble in water than in electrolyte. As these crystals are dissolved, the sulfate is converted back into sulfuric acid and the specific gravity rises. This procedure will only work with some batteries. ''
from
https://www.pacificpowerbatteries.com/aboutbatts/Car%20Battery%20FAQ/carfaq16.html