Optima and Exide Orbital

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

There is a bit of spin there Stan - and I'll try to go through it - I love equations but will try without them.

The first point about using 100% relates to the batteries internal resistance.

You have seen those adds on TV saying lithium camera batteries will give you 500 photos on your digital camera when ordinary battires only give 20.

Well its true and at first you might think that lithium batteries hold (500/20) or 25 times as much power , but they don't and a quick look at there specs shows they hold less than twice as much as ordinary batteries.

The trick is that Lithium can handle very heavy loads just like Orbitals , both because they have low resistance inside and so maximum current can get out.
Great for winching.

So if powering a big fat load the Orbitals deliver more and last longer.
If however you put a small load on your Orbital it won't last any longer than normal car battery of equivalent rating.



The second issue is depth of discharge and Oribatls can be discharged further without damage and will recharge faster - again because of lower internal resistance.
The Orbitals are however significantly heavier for the same rated capacity so if you re-arrange the figures based on weight they are much the same.

Orbitals can give you more wack in a smaller size and I have used them however
the capacity they have is usually not enough to power a camp site for long so you need two.

We run light weight and need little capacity and for us the best equation is to run a single 80 odd AH battery like Overlander/ Exide extreme in N70 size as per another recent post as they can be squeezed into much the same space as your N50 Orbital (which has a funny shape).

You do run them down to far sometimes and this shortens life but your typical 3 years is not bad and I prefer to replace early rather than risk failure.

Thanks Peter and Robin.
If the sum total of the benefit is about 50 more cycles until its cooked ie 300 times as opposed to 250......
Well, I nearly got taken in there.