how much longer can my car battery last?

[Semidevil]

so just had my oil change and they also checked the battery. the printout states: "Replace Battery."

voltage: 12.9V
measured: 297CCA
rated 400 CCA
temp: 72' F

I'm just curious to know how to read this, and how to interpret this. How much longer can the battery last realistically?

 

[Kaervak]

According to the info, your battery has lost 25% of it's cold cranking amp capacity at a temperature of 72F. Since it's rather hard to test the battery at a temp of 0F in September, the true CCA is unknown. Since it's down 25% in warm weather, it's probably going to be down a good bit more in the winter. How old is this battery?

 

[ChaosDivine]

You probably won't have any troubles in warm weather. Soon as witch's tit weather hits, you're going to have trouble starting.
What group size is your battery? Can't be overly expensive.

 

[VinylxScratches]

I still have the original battery in my Dodge Neon. I'm at 71,000 miles. I wonder if it will make it through this winter. The car is from 2002.

 

[Zenmervolt]

Originally posted by: Kaervak
According to the info, your battery has lost 25% of it's cold cranking amp capacity at a temperature of 72F. Since it's rather hard to test the battery at a temp of 0F in September, the true CCA is unknown. Since it's down 25% in warm weather, it's probably going to be down a good bit more in the winter. How old is this battery?

CCA is a corrected number. That's why they are listing CCA (Cold Cranking Amps, which, by definition, is the amperage available at 0 degrees Fahrenheit) and not simply CA (Cranking Amps).

To arrive at CCA, they have measured CA and the ambient temperature and then used a correction factor to calculate CCA for the battery using a mathematical formula. Your comments about the battery being down even more in cold weather are invalid.

To the OP: A charge of 12.9 volts indicates that your car's charging system is performing properly and is maintaining a 100% state of charge for your battery.

CCA is the amount of amperage that can be delivered at 0 degrees Fahrenheit for a period of 30 seconds without the total battery voltage drops below 7.2 volts. In warm weather the battery will deliver significantly more amperage. When determining CCA, the Cranking Amps are measured at ambient temperature and then a mathematical correction is applied to determine what the CCA is. If the measured CCA is 297 Amps, then the battery put out significantly more amperage at the 72 degree ambient temperature.

Rated CCA is the spec CCA for the battery based on the manufacturer's sticker. Most batteries do not test at exactly the rated CCA even when brand new due to slight variances in manufacturing.

Most starters will not draw more than 150-200 amps even for large V8 engines. Given that your battery was speced at 400 CCA, it is likely that you have 4-cylinder car. This means that your starter will probably draw, at most, 100 amps under load. While this may increase slightly in very cold climates, chances are that even on a 0 degree day your car's electrical system will not draw more than 200 amps total when starting (let's say 125 amps for the starter plus 75 amps for miscellaneous auxiliary systems).

While it's not a bad idea to replace the battery at this point (especially if it's 5 years old or more), chances are that it would still get you through this next winter unless you live somewhere that gets extremely cold (well below zero).

ZV

 

[cprince]

Originally posted by: VinylxScratches
I still have the original battery in my Dodge Neon. I'm at 71,000 miles. I wonder if it will make it through this winter. The car is from 2002.

It's time to replace the battery. In my experience and what I read, most lead-acid batteries last about five years. The one in my car is over four years old, and I can feel that it's getting weak--the crank is not as "clean" anymore.

 

[Kaervak]

Originally posted by: Zenmervolt

Originally posted by: Kaervak
According to the info, your battery has lost 25% of it's cold cranking amp capacity at a temperature of 72F. Since it's rather hard to test the battery at a temp of 0F in September, the true CCA is unknown. Since it's down 25% in warm weather, it's probably going to be down a good bit more in the winter. How old is this battery?

CCA is a corrected number. That's why they are listing CCA (Cold Cranking Amps, which, by definition, is the amperage available at 0 degrees Fahrenheit) and not simply CA (Cranking Amps).

To arrive at CCA, they have measured CA and the ambient temperature and then used a correction factor to calculate CCA for the battery using a mathematical formula. Your comments about the battery being down even more in cold weather are invalid.

To the OP: A charge of 12.9 volts indicates that your car's charging system is performing properly and is maintaining a 100% state of charge for your battery.

CCA is the amount of amperage that can be delivered at 0 degrees Fahrenheit for a period of 30 seconds without the total battery voltage drops below 7.2 volts. In warm weather the battery will deliver significantly more amperage. When determining CCA, the Cranking Amps are measured at ambient temperature and then a mathematical correction is applied to determine what the CCA is. If the measured CCA is 297 Amps, then the battery put out significantly more amperage at the 72 degree ambient temperature.

Rated CCA is the spec CCA for the battery based on the manufacturer's sticker. Most batteries do not test at exactly the rated CCA even when brand new due to slight variances in manufacturing.

Most starters will not draw more than 150-200 amps even for large V8 engines. Given that your battery was speced at 400 CCA, it is likely that you have 4-cylinder car. This means that your starter will probably draw, at most, 100 amps under load. While this may increase slightly in very cold climates, chances are that even on a 0 degree day your car's electrical system will not draw more than 200 amps total when starting (let's say 125 amps for the starter plus 75 amps for miscellaneous auxiliary systems).

While it's not a bad idea to replace the battery at this point (especially if it's 5 years old or more), chances are that it would still get you through this next winter unless you live somewhere that gets extremely cold (well below zero).

ZV

Learn something new everyday. I had no idea there was a way to calculate the CCA of a battery in a warm environment.