First off, I have a very heavy, unique Teleco Surplus battery... It was new and in service probably in December of 2014, and I picked it up around August 1st, 2015. Previous history is an unknown.
What I think I know is this... I take 35-40 amps out of it in a 24 hour period. You can take probably 12 amps off of that as parasitic drag in the day time when solar panel is charging as best it can from 7.5 to 8.8 amps/hr. Solar panel is a 150W 12V job.
Charging with the Mega Watt, I've taken at most 12 amp hours out of the battery, and at 14.43V setting at the Mega Watt terminal, not at the battery, I've seen at most, 20 amp hour take rate for charging, intially.
Having charged it 3X now, fully, here is what works for my Acid Rich 1.300SG very thick lead plated 10 year warranty battery... If my V on MegaWatt is set at 14.40V, I will continue to charge until I see a C factor of "0.01" or 1% factor of amp hour ratings. That means if my battery is rated for 150 amp hours, when I see 1.5Amps/hr charge rate "take" rate by the battery, I am done.
Deka, the manufacturer of my battery, however, recommends a float voltage of 13.48 -13.52V. When I dial back the Mega Watt with the 10 screw pot to 13.50V, immediately after the charge above, a float voltage, if you will, 3x now, the amp charge rate will be at the suggested 1/2 of 1% charge take rate, or .75 amp/hr.
My battery does not seem to drop to 0 amps taken. Finished voltage for my battery, depending on external temps, after 72 hours, runs 12.88V at 95F and 12.86V at 83F.
YMMV, my battery is unique in it's charging needs, but it's designed to last a long, long, long time.
Buy a battery and ask the manufacturers's engineer with a phone call, what to expect, and take notes, and write them down and engrave them on your brand of battery.
My battery usage, and charging seem to indicate that I do not get deeply discharged very often. If I stay in the 70 to 75% SOC range each morning, the MegaWatt really doesn't seem to get much "grunt" going on at start up, in terms of having the battery slurp a lot of amps out of the Mega Watt. Why this is, and why my battery charges slower than most AGMS, is, my guess, a function of design, and low number of heavy, thick lead plates. Not alot of plate surface will yield lower charge rates.
