What an Optima is, was "Do I want an Optima?

[Bluemaxww1 at aol.com]

Thank you for this detailed explanation.  I have saved it so I can  remember 
down the road.  I love it.
 
Greg W.
 
In a message dated 9/19/2006 5:31:13 P.M. Pacific Daylight Time,  
erwendell at mac.com writes:

know I'm  weighing in a little late on this one (been busy fixing  
airplanes)  but because I have a lot of experience with these things I  
wanted to  go on record anyway. My school has an electric powered open  
wheel  race car that has 28 Optimas on board and we have multiple  
battery  packs. We are constantly using, capacity testing, and  
charging these  things.

What they are not is "sealed" "dry cell" or any other  adjective  
Optima, their promoters, or self proclaimed experts apply  to them.  
They are a lead acid battery at the core. They do have a  liquid  
electrolyte of sulfuric acid. If you poke a hole in the side  of the  
case acid will not gush out of the hole but if you poke your  finger  
in you will get acid all over it. This is because the space  between  
the plates is filled with fiberglass mat. The mat wicks up  and holds  
the electrolyte but at the same time allows the various  ions within  
it to transfer between the plates thus requiring less  electrolyte  
than a conventional lead acid battery. This class of  lead acid  
batteries is know as AGM for Absorbed Glass Mat and there  are many  
others including the Concord, Hawker Genesis, Odyssey, and  others.  
The unique feature is the fact that the plates for each cell  are  
wound up into a cylinder rather than just left in a  rectangular  
shape. AGM batteries in general have a lower internal  resistance than  
a conventional flooded cell battery and therefore a  higher maximum  
current. This feature is useful in really really cold  climates or  
very high demand situations such as electric race cars  or starting  
jet engines.

Now to the "sealed" part of the  equation. They are not technically  
sealed but are instead part of  another lead acid technology called  
valve regulated gas recombinate  batteries. In this respect they are  
like all "maintenance free" lead  acid batteries where the gasses that  
are generated during normal  operation are forced to recombine into  
water by way of pressure.  This means that the case is under  
considerable pressure during  normal operation which for safety  
reasons means that there must be a  pressure relief valve. If you look  
at the top of an Optima you will  see two white discs that are in fact  
filters that sit on top of the  pressure relief valves. If the  
internal case pressure gets high  enough these valves will open and  
vent gasses if the batter is  upright and liquid if oriented any other  
way. If there is any  discoloration of the disc then the battery has  
vented at some point  and due to the decreased electrolyte content  
will have a reduced  capacity. Granted, during normal operation this  
won't happen. The  listed exception is excessive charge current which  
produces gas at  too rapid a rate and therefore the battery vents.  
This would occur  is the voltage regulator failed in a short condition  
which is fairly  common. I have personal experience however of an  
Optima venting  under discharge and as it was installed sideways there  
was a puddle  of electrolyte in the battery box. That battery went  
straight to the  recycle pile. The discharge rate wasn't excessive but  
it was a  sustained discharge such as would occur if the charging  
system  failed.

Now as to my opinion. While interesting from a technical point  of  
view, I don't see any advantage of spending the extra money on  the  
Optima for your application. It's not lighter than the  standard  
battery and you don't require the high current rating  because your  
starting system was designed for conventional  batteries. If you were  
looking to install a much smaller battery to  save weight than an AGM  
battery makes sense because they have a much  higher CCA rating than  
an equivalent size conventional battery. This  is why a little PC680  
Odyssey can start a full size car. What isn't  apparent to most people  
though is that you can't get something for  nothing. A smaller battery  
has less capacity so if the charging  system quits in a vehicle  
equipped with one of those tiny batteries  they would be lucky to get  
to the next interstate exit before the  car comes to a halt. You also  
can't count on any "sealed" battery to  never vent gas into the  
interior where as the proper battery with  the vent hose connection  
can't. As a bonus, the vented battery will  last longer provided you  
think about topping off the cells with  distilled water. Also, the  
professor who is the advisor for the race  team says that Optimas are  
inappropriate for any application where  they will be subject to a  
constant overcharge such as in an  automotive electrical system. I  
can't remember the exact reason but  I defer to him on this point.

Roy Wendell
erwendell at mac.com
Too  many type 44 tq
A pair of MR2s