Adding water to AGM battery?

Almot wrote:
Mex, Why bypass the controller? I think they recommend conditioning at steady 15.5. If you bypass the controller and disconnect the loads, the voltage on the battery will eventually rise up to the voltage of the panel, which is well above 15.5 even for a nominal 12V panel.

Besides, a good controller will have either Equalizing mode - that allows charging at adjustable voltage around 15-16, or an adjustable Absorption setpoint - this one is usually a little under 15.5, but close enough.

I assumed the worst being a controller with no deluxe features and "eventually" is a long enough time even to allow even the laziest (this includes me) to wander over to the bypass wire and snag it. Where this formula runs into trouble is when an array is far larger than the recommended 5% of amp hour limit. Like trying to stuff 20 amperes into a 100 amp hour RV battery. Few RV's are equipped as such with too much photovoltaic muscle.

Trends and tendencies: An AGM battery under conditioning cycle will allow the voltage to rise until it seemingly hits a brick wall, sometimes as low as 14.5 volts. There the voltage stops climbing and this is what you are shooting for. When the voltage resumes its climb a good portion of the occluded plates have been "conditioned" about as well as they're ever going to get. Continue on to 15.5 if voltage is increasing slowly but if voltage is steadily rising quickly, the exercise is over. No sense in jamming unwanted wattage into the battery.