Which Battery Ratings Should We Care About in Car Audio (CCA, AH, ESR, etc.)?

[lostdaytomorrow 10+ year member]

I am looking to have an educational thread on the ratings of the batteries we use in car audio applications, and how to know how certain batteries compare to others.

This is not a thread for the discussion of High Output Alternators or any argument for or against them in a car audio application, because we assume that if one is looking into getting some extra batteries in the back, you should naturally have a HO Alt. already.

Which rating(s) should we care about and why?

For example, a Kinetik 2400 (or Optima yellowtops, XS Power, etc.), which is marketed towards our crowd vs. a battery that is made for the computer backup crowd (such as the Sprinters, Datasafes, etc.).

One problem we face in our market is that the batteries we buy do not always have all of the ratings that we are interested in posted from the manufacturer.

Here are some of the ratings we can look at when it comes to batteries: We need to decide which are important for car audio applications and which are non-important.

This discussion deals mainly with secondary batteries, and assumes the user has a sufficient AGM deep cycle under-hood battery already.

Definitions from Wiki follow:

1. AH: Ampere-hours (A·h) is the product of the time that a battery can deliver a certain amount of current (in hours) times that current (in amperes), for a particular discharge period. This is one indication of the total amount of charge a battery is able to store and deliver at its rated voltage.

2. Cranking amperes (CA), also sometimes referred to as marine cranking amperes (MCA), is the amount of current a battery can provide at 32 °F (0 °C). The rating is defined as the number of amperes a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery).

3. Cold cranking amperes (CCA) is the amount of current a battery can provide at 0 °F (−18 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). It is a more demanding test than those at higher temperatures.

4. Hot cranking amperes (HCA) is the amount of current a battery can provide at 80 °F (26.7 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery).

5. Reserve capacity minutes (RCM), also referred to as reserve capacity (RC), is a battery's ability to sustain a minimum stated electrical load; it is defined as the time (in minutes) that a lead-acid battery at 80 °F (27 °C) will continuously deliver 25 amperes before its voltage drops below 10.5 volts.

Also, keep in mind that Peukert's Law expresses the fact that the capacity available from a battery varies according to how rapidly it is discharged. A battery discharged at high rate will give fewer ampere hours than one discharged more slowly.

There are some other ratings which might be important in car audio applications such as the resistance inside the battery, usually measured in milli-ohms. We want this to be a small number so the current can be discharged quickly and efficiently to our amps.

And of course we have all heard that random rule thrown around that we need 100aH of batteries per a certain number of watts, or any other random rules thrown around. I'd like an enlightening explanation on any of these rules, because the large battery manufacturers sure don't go by that rule if you check the aH ratings on the main car audio specific batteries.

So, which rating(s) should we care about and why?

All input and educational posts are welcome.

It would also be nice for people with high wattage systems and extra battery(ies) to explicitly list their electrical systems along with total RMS wattage of their amplifiers to get some anecdotal evidence all in one place.

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[cotjones 10+ year member]

I am looking to have an educational thread on the ratings of the batteries we use in car audio applications, and how to know how certain batteries compare to others.
This is not a thread for the discussion of High Output Alternators or any argument for or against them in a car audio application, because we assume that if one is looking into getting some extra batteries in the back, you should naturally have a HO Alt. already.

Which rating(s) should we care about and why?

For example, a Kinetik 2400 (or Optima yellowtops, XS Power, etc.), which is marketed towards our crowd vs. a battery that is made for the computer backup crowd (such as the Sprinters, Datasafes, etc.).

One problem we face in our market is that the batteries we buy do not always have all of the ratings that we are interested in posted from the manufacturer.

Here are some of the ratings we can look at when it comes to batteries: We need to decide which are important for car audio applications and which are non-important.

This discussion deals mainly with secondary batteries, and assumes the user has a sufficient AGM deep cycle under-hood battery already.

Definitions from Wiki follow:

1. AH: Ampere-hours (A·h) is the product of the time that a battery can deliver a certain amount of current (in hours) times that current (in amperes), for a particular discharge period. This is one indication of the total amount of charge a battery is able to store and deliver at its rated voltage.

2. Cranking amperes (CA), also sometimes referred to as marine cranking amperes (MCA), is the amount of current a battery can provide at 32 °F (0 °C). The rating is defined as the number of amperes a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12 volt battery).

3. Cold cranking amperes (CCA) is the amount of current a battery can provide at 0 °F (−18 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). It is a more demanding test than those at higher temperatures.

4. Hot cranking amperes (HCA) is the amount of current a battery can provide at 80 °F (26.7 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery).

5. Reserve capacity minutes (RCM), also referred to as reserve capacity (RC), is a battery's ability to sustain a minimum stated electrical load; it is defined as the time (in minutes) that a lead-acid battery at 80 °F (27 °C) will continuously deliver 25 amperes before its voltage drops below 10.5 volts.

Also, keep in mind that Peukert's Law expresses the fact that the capacity available from a battery varies according to how rapidly it is discharged. A battery discharged at high rate will give fewer ampere hours than one discharged more slowly.

There are some other ratings which might be important in car audio applications such as the resistance inside the battery, usually measured in milli-ohms. We want this to be a small number so the current can be discharged quickly and efficiently to our amps.

And of course we have all heard that random rule thrown around that we need 100aH of batteries per a certain number of watts, or any other random rules thrown around. I'd like an enlightening explanation on any of these rules, because the large battery manufacturers sure don't go by that rule if you check the aH ratings on the main car audio specific batteries.

So, which rating(s) should we care about and why?

All input and educational posts are welcome.

It would also be nice for people with high wattage systems and extra battery(ies) to explicitly list their electrical systems along with total RMS wattage of their amplifiers to get some anecdotal evidence all in one place.

I Usually pay the most attention to the Ah and CCA's. Since its car audio battery and not going to be drained at the CCA rating at all times the Ah rating is a useful indicator of how well the battery will perform in your given application, Yet the CCA is also useful to give you an indication of the batteries maximum efficient load.

A rule of thumb I like to go by is to have enough CCA to at least triple to quadruple the maximum draw of your system at any given point, then from there the higher the amp hour rating, the better.

IE: If i'm running an amp that can draw 200Amps MAXIMUM I want 600 - 800 CCA's and the higher amp hour the better.

 

[RAM_Designs 5,000+ posts]

I always do 100ah(or more most of the time) of extra battery per 1kw of power over 1kw. Since I can run a 1kw amp easily on my stock alt, then for a 2kw amp I'll add 100ah, 200ah for a 3kw amp, and so on. Without upgrading the alt the voltage will easily drop down to battery voltage, around 12.5-13V, but having those extra batts will keep it from dropping any further.

 

[lostdaytomorrow 10+ year member]

Well, looks like I'm the only that doesn't know everything about batteries.

 

[lostdaytomorrow 10+ year member]

Any more input?