I'm looking at buying batteries, either 12v AGM or LI-Ion, for use in a backup power system. I have a choice between a Lifeline 8D AGM battery rated at 255 Ah @ 20 hr, or a Victron LI-Ion rated at 160 Ah @ 20 hr.
Because the depth of discharge between the two is different (50% for AGM vs 80% for LI-Ion), I have to wonder if the Ah rate takes into account voltages at different states of charge.
I seem to recall that Ah ratings are based on how long a battery can produce a given ampacity before it drops below 12v. Does that mean an AGM battery rated for 255 effectively only gets 127.5 Ah because of a max 50% discharge depth? Or is it 255 total Ah before it reaches the point at which it's no longer producing 12v? Or is depth of discharge just a consideration for battery life?
I can obviously get much more for my money with the Lifeline AGM 8D vs the Victron Lithiums, but I want to make sure I'm getting the full advertised capacity.