Originally Posted By: wrcsixeight
Kept at 100% state of charge on a temperature compensentated float charger at or below 75F the top of the line AGM manufacturers are claiming 12 years service life.
At the end of this 12 years, how much CCA would remains, how long could it power a load in accordance with its performance when new?
UNknown.
Usually when a battery has only 80% of its original capacity it will be taken from service as failure rates increase exponentially after that. I do not believe there is a standard which all battery manufacturers use when making such claims in standby use. Like when it tests at X percentage of original CCA, or has declined to X percentage of capacity.
One must also realize that a 650CCA battery can decline to 250CCA and still be able to start the engine, until those freezing temps hit, and perhaps even then.
The Benchmark of being able to start the engine in mild or warm temperatures, does not determine whether a battery is healthy or not as it requires only a tiny fraction of the battery capacity to do that task, and most starters use a tiny fraction of amps of that CCA rating
I have seen my starter use as much as 164 amps. Yet my owner manual stipulates a battery with a minimum of 550CCA.
I have started it on a 12AH AGM battery which would be lucky to achieve a 150CCA rating, granted it was very slow and just barely caught, but it caught.
Lead acid Batteries have shelf lives regardless if they are ever used or not. the shelf life can be extended with a temperature compensated maintenance/float charger and when kept at cooler temperatures. How long can it be extended? I do not know, and it would likely take 15 years or more to determine an answer on a battery available today recharged fully and put on a temperature compensated maintenance charger and put in a refrigerator.
In 15 years who knows what kind of battery technology will be in use.
In 15 years likely lead acid batteries will still be in wide use.
For energy applications, new vs used ampere-hours are what is the consideration. Condemnation at 80% of original.
Total Ah is not critical for SLI applications. They arent depleted the same way. This is where impedance is more critical. Impedance defines the voltage drop under load. Since the impedance of different size batteries differs, the better metric is wen voltage drops below some condemnation value (10.8V or so) when loaded at half its CCA rating.