Toyota Repair: Battery replacement?

Question
QUESTION: Last week the service dept. at Toyota replaced the A/F filter on my 2003 Camry and this involved some work with the computer. After the servicing the car stalled out and then I restarted it. I suspected that the servicing may have caused this, but also I thought of idling speed and battery. I called AAA to check the battery and they said its at 100%, even though I installed it just under 4 years ago. (6-year battery). But the readout said the average battery life (L.A. area) is 48-53 months. So I figure I need to replace it son. Question: why does a battery check say 100% after I've used it about 4 years? Shouldn't it say something like 25%. Is it similar to a container of water being drained out after years of use or am I thinking about this in the wrong way? Why is the average life of a 6-year battery "48-53 months?" Thanks.

ANSWER: Hello
Wet cell batteries have a tendency to degrade very quickly after a certain amount of time, when they check it they refer to the state of charge which can be 100% which means it is fully charged at 12 volts to 12.5 volts, it does not represent the integrity of the battery, only that it is charged 100%, car batteries can fail over a short period of time, within a few days, the problem is that any battery will discharge even without use, when a battery does not accept charging anymore it will fail in a short time. So what I'm saying is that a 4year old battery may check at 100% charge today and still fail in a few days because of a bad cell or degraded material which causes it to not accept charging anymore, hope this makes sense and keep in mind the "average life" is just that, an average that means 50% last longer and %0% last a shorter time.

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QUESTION: OK, so if the average life of a 6-year battery is actually about 4 years, then why does the manufacturer call it a 6-year battery?

Answer
They can call it whatever they want, it just means that the say it's a six year battery because there is a six year warranty, if it fails sooner they "pro rate it" that means they replace it but you will have to pay a portion of the cost depending how close it failed before the six years is up. For example if it fails after three years they give you a new battery but you pay half of the cost. For more battery warranty information and disclaimers etc. you can contact any one of the manufacturers or their retail outlets, they are most likely not all the same.