and maybe DWH has some thoughts too.
Well, it's a bit like voltage drop through wire. Most people do the math and figure they need some big wire like a #8 or whatever because the voltage drop is X.
The gotcha there, is that the voltage drop is going to be X at
Y amperage of load. As the voltage of the battery rises, its resistance rises, and the amperage flow reduces, and so, as you approach the top of the charging cycle, the voltage drop *becomes less and less*.
Even with a small wire you'll
eventually get the voltage of the battery up to equal whatever the voltage of the bus is. It'll just take longer because the resistance of the wire at Y amp flow will limit how many amps can get to the battery, by limiting the voltage available to push the amps - at first. But that limiting will eventually go away.
The Odysseys are made with a buttload of thin lead plates - what would normally be considered a "cranking battery" design. But they've got theirs setup so it also does just fine as a deep cycle as well. One advantage of their design, is that you can dump unreal amounts of amperage into that unit without hurting it. They even include C*4 charge rates in the specs in their tech manual.
That would be
400 AMPs of charge current, for a 100ah battery!
800 AMPs for a 200ah bank!
Recharge a 100ah battery in 15 minutes!
Hoo boy. I use the word 'unreal' with malice aforethought - sure the battery can handle it, but who in hell has that much charger available? A nuclear sub could probably get it done.
Optimas have a different plate design. They use a 'spiral wound' plate layout. That gives them a lower resistance, but doesn't allow such massive charge currents.
Each design, has its own resistance *curve*.
And battery resistance curves are basically the opposite of what voltage drop does - as you get less resistance through the wire as the battery approaches fully absorbed, you get more resistance through the battery.
So, to plot a charge curve, you have to take into account the variables of wire resistance decreasing, and battery resistance increasing, AND the voltage of the bus that is supplying the current to the batteries.
So, it makes perfect sense to me, that 150ah of spiral wound lead-acid could potentially absorb more amps faster than 100ah of thin plate lead-acid -
when being charged by a constant voltage charger such as a 13.8v bus voltage, vehicle alternator/voltage regulator system, or a small (10a-25a) mains powered charger.
But then again, you could hook up a 3-stage 100a Xantrex Prosine to charge the Odyssey and pump it up quick, which would probably make the Optima pop like a balloon.
Hell, if you were nuts (or in the Navy), you could hook up TWO (or THREE or
FOUR!) of the 100a Xantrex chargers to the Odyssey and not even void the warranty. Of course, you would certainly trip the 15a or 20a breaker on the house electrical panel if you tried it.
