I'm taking some mild interest in this thread, as the battery in my '2000 300M must be nearing the end of it's life (it will be 5 years old this november).
I don't necessarily believe that the Optima line of batteries is the "best" from an energy density point of view (the spiral design does not make the best use of the available rectangular exterior envelope compared to conventional battery construction). It might very well be that shelf-life was the over-riding design criteria for this battery. Shelf life is probably _the_ most important issue for retailers.
Cold Cranking Amps (CCA) and reserve capacity are probably the two most important numbers to look at when selecting a battery since other objective criteria, like MTBF, accelerated life tests (vibration and temperature extremes) are not readily available to compare across manufacturers. Unlike many other types of consumer products (digital cameras, car tires, many electronic product, etc) there are no third-party-operated web sites that track, organize, and tabulate the experience of consumers when it comes to car batteries, let alone take the batteries apart and make subjective comparisons between manufacturers (as has been done with oil filters for example).
This web site:
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will give you the CCA number given engine size and # of cylinders as inputs. For example, a 3.5L V-6 (214 cubic inches) gives a computed CCA of 285.
It is generally the consensus that you should NOT sacrifice reserve capacity for the sake of having a large CCA. For example, if I had the choice between the following batteries:
A) 400 CCA and 120 minutes reserve capacity B) 800 CCA and 90 minutes reserve capacity
Then it seems that battery (A) will, in the long run, be a better choice because I'm not likely to ever need more than 400 CCA while on the other hand the extra 30 minutes of reserve capacity may actually be needed at some point. In other words, batteries can never convert un-needed CCA's into extra reserve minutes.
One thing must always be kept in mind. Once you choose a battery make and model, buy the "freshest" battery in store (which, it seems, will not necessarily be on the battery rack but instead in the back room).
I found the following web site to have useful battery information:
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And particulary these pages:
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This paragraph is interesting:
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7.6. Freshness
Lead-acid batteries are perishable and sulfate in storage due to their natural self discharge. Please see Section 16 for more information on sulfation.
Determining the "freshness" of a battery is sometimes difficult. Unless it has been periodically recharged or "dry charged", NEVER buy a wet Standard (Sb/Sb) or Low Maintenance (Sb/Ca) battery that is MORE than three months old or a wet Maintenance Free (Ca/Ca) battery that is MORE than six months old. Dry charged batteries are shipped without electrolyte, but usually have "sell by" dates of one to three years. Depending on the temperature, AGM and Gel Cell batteries that can be stored six to 18 months before the State-of-Charge drops below 80%. Please see Section 16. for more information on sulfation. Dealers will place their older batteries in storage racks so they will sell first and they do not have to maintain them. The fresher batteries can be found in the rear of the battery rack or in a storage room. For a wet battery, the date of formation is often stamped on the case or printed on a sticker. Always have a new battery tested, and recharged if necessary, before you leave the store. This can save you a lot of time and frustration if the new battery is sulfated or has a manufacturing defect.
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Here is the complete section on battery date codes:
------------ The battery date codes for various manufacturers is perhaps the most useful information to have when you're actually at the parts counter about to buy a battery.
Some of the manufacturer's formation date coding techniques are as follows:
7.6.1. Delphi (ACDelco) and some Sears DieHard
Dates are stamped on the cover near one post. The first number is the year. The second character is the month A-M, skipping I. The last two characters indicate geographic areas. For example, 0BN3=2000 February.
[Source: Interstate Batteries]
7.6.2. Douglas
Douglas uses the letters of their name to indicate the year of manufacture and the digits 1-12 for the month. D=1994 O=1995 U=1996 G=1997 L=1998 A=1999 S=2000 For example, S02=2000 Feb.
7.6.3. East Penn, Exide (Champion), Johnson Controls Inc., Interstate, Mopar (Chrysler) and some Sears DieHard)
Usually on a sticker or hot-stamped on the side of the case. A=January, B=February, and the letter I is skipped. The number next to the letter is the year of shipment. For example, B0=Feb 2000.
[Source: Interstate Batteries]
7.6.4. Exide (some Sears non-Gold DieHards)
The fourth or fifth character is the month. The following numeric character is the year. A-M skipping I. For example, RO8B0B=February
2000.
[Source: Interstate Batteries]
7.6.5. Optima
The first character is the year. The following three numeric characters are the days of the year. For example, 3123=3 May 2003.
7.6.6. Trojan
The date code on the negative post is stamped as the battery comes off of the finishing line, ready to ship out or go into stock. The code that is stamped is usually one month ahead. Therefore, a battery that comes out in March will carry an April date code. The code on the positive post is the manufacturing date that indicates when the battery was physically built but before the addition of any electrolyte. The letter is the month (A=Jan, B=Feb, C=March, etc.) and the number is the actual date. So "K26" means that the battery was ready for electrolyte filling and the first forming charge was on November 26th. Since the negative post shows A2 (January 2002), the manufacturing year has to be 2001.
7.6.7. Concorde
The activation date is on an orange sticker the shipping carton or email Concorde Customer Service with the serial number of the battery.
7.6.8. Rolls and Surrette
The four digit date code represents the day of the week (first digit), week of the year (middle two digits) and the year (last digit). For example, April 4, 2003 would have 4143 as a date code. The date code is stamped into the front edge of the cover of the battery.