What's the point of a new battery if the alt can push what the amp needs?

[akillj 10+ year member]

Other than using things while the car is off, is there any real advantage to using a new battery if a h/o alt can supply what the amp needs?

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[keep_hope_alive Premium Member]

because batteries are also loads. old batteries float at lower voltages or act as a constant drain on the alternator - so they subtract what the alternator can provide.

a car with a good battery that floats near 13V will have an easier time maintaining 14V compared to the same car with an old battery that floats around 12V.

alternator output is relative to engine RPM. at idle, that output drops to half or lower. if you are at idle and playing the system loud enough, the battery is forced to support the system and car. the drop in supply voltage will decrease voltage rails in most amplifiers, reducing available power and sometimes causing clipping.

in the end, the electrical system is only as good as the weakest link. a good battery is the foundation to any automotive electrical system.

also, good AGM batteries are excellent current sources and respond much faster than the alternator. for good transiet response, good batteries are required.

 

[akillj 10+ year member]

because batteries are also loads. old batteries float at lower voltages or act as a constant drain on the alternator - so they subtract what the alternator can provide.
a car with a good battery that floats near 13V will have an easier time maintaining 14V compared to the same car with an old battery that floats around 12V.

alternator output is relative to engine RPM. at idle, that output drops to half or lower. if you are at idle and playing the system loud enough, the battery is forced to support the system and car. the drop in supply voltage will decrease voltage rails in most amplifiers, reducing available power and sometimes causing clipping.

in the end, the electrical system is only as good as the weakest link. a good battery is the foundation to any automotive electrical system.

also, good AGM batteries are excellent current sources and respond much faster than the alternator. for good transiet response, good batteries are required.

Very informational! Thank you!