Sunday, Jul 03, 2011 at 19:33
Hello again Stan,
spiral wound AGM batteries have very thin electrodes, 1mm and less. But due to the spiral wound build, the interface area electrode/electrolyte is very large. This means that much of the charge is stored at or slightly below the electrode's surface. This makes for a very low internal resistance which is good for high current densities both for charging and discharging.
Therefore, the discharge curves are quite 'flat', only dropping off sharply when almost fully discharged.
...it possible to use 100% of the stored power in the Op.ima compared to ordinary batteries..
You can do this with any AGM battery as long as it's rated 'deep cycle'.
Do this about 250 times with a flat plate AGM, and 300 times with a spiral wound AGM and then they're toast. Paramount for achieving this is that they need to be fully charged before taken down to 0% SOC.
The spiral wounds also greatly benefit from an equalisation stage in this case, for reasons given below:
If the batteries have been operating under partial state of charge for some time, this means that some cells have been weakened by negative electrode sulphation, then these cells can be reverse charged during this exercise, killing the battery.
To prevent this, Op.ima recommend to apply an equalisation charging stage for their deep cycle range (this ensures all cells are of equal capacity, in the hope that none gets charged in reverse during really deep discharges).
Spiral wound batteries are a bit more temperamental in the deep cycle department compared to flat plate AGM deep cycle ones which don't show this effect as readily.
If you want a battery for deep cycle applications, down to 20% DOD, you can't go past flat plate 'deep cycle' AGM batteries.
Spiral wound ones on the other hand, have the edge in extreme high current applications like cranking, and winching, and have somewhat higher extreme temperature tolerance, but not much.
So if you need the battery predominantly for starting/winching with a small footprint, and occasional deep cycle discharges, then select spiral wound.
If daily deep cycling is on the cards, and only occasional cranking (in emergency situations), select flat plate 'deep cycle' AGM.
Flat plate only cost half as much to manufacture, so if you're purely after max Ah, at the smallest cost, go for flat plate 'deep cycle' AGM.
cheers, Peter
AnswerID:
459101