If you have experience with car batteries, then you probably know that they come in different voltages, with the 12-volt battery being the most common type to power vehicle components. But how many amps do these batteries have?
Knowing your car battery’s amp rating is important for choosing the right battery for your car and running it safely. The amp capacity of a battery determines how long it can work without being charged, what electronic accessories it can power in your vehicle, and how long it takes to charge the battery.
In this article, I’ll discuss the amp rating of a 12-volt battery and how to measure your car battery amps.
Table of Contents
What is the Amp Rating of a 12 Volt Battery?
In order to make sense of this question, you first need to understand the key electrical term in your car battery systems, as well as the various categories of rating a car battery capacity.
1. Amps (Amperes)
An amp, or ampere, is a unit of measurement for electrical current. Current is defined as the rate at which electrons flow through an electrical conductor. In this case, the conductor is your battery. Measuring amps is important for understanding how your battery works and troubleshooting problems.
2. Amp-hour (AH)
This is the most common battery capacity rating. Amp-hour refers to the maximum amount of current that a battery can store and produce over time before it needs to be recharged.
For example, a 100Ah battery can provide a current of 1 amp for 100 hours or 5 amps for 20 hours.
Most car batteries typically have an amp-hour rating of 50Ah to 100Ah, whereas large or diesel-powered trucks use 100+ Ah batteries with 1000+ CCA.
3. Cold Cranking Amps (CCA)
CCA measures the maximum amount of current that your battery can deliver at a certain amount of time in cold weather. For example, a battery, when fully charged, can deliver up to 30 seconds of current at 0°F (-18°C) without the voltage dropping below 7.2V.
The Cold Cranking Amp (CCA) rating is an important value because it indicates how a battery will perform during the cold season, and it is often the first thing to look for when purchasing a starting battery.
A 12-volt car battery has an average Cold Cranking Amps rating of around 650 CCA. Although some compact vehicle batteries have a CCA of 400 to 600, larger vehicles such as SUVs and trucks use batteries with a higher CCA of 700 to 1000.
4. Cranking Amps (CA)
The CA rating is the maximum current that a fully charged battery can deliver for 30 seconds at 32°F (0°C) without dropping below 7.2V. It is also referred to as hot cranking amps (HCA) or marine cranking amps (MCA) because it indicates how a battery will perform in hot weather or marine condition.
Cranking Amps for a 12-volt car battery can range between 400 and 750 CA.
5. Battery Reserve Capacity (RC)
The battery reserve capacity measures a 25amps supply rate of a fully charged battery at an ambient temperature of 80° F before dropping below 10.5volts
For example, if a lead acid battery’s RC rating is 120, it means the battery can provide 25 amps for 120 minutes before losing power to start the car.
The typical RC rating for 12-volt car batteries is between 100 and 120. This means that the batteries can deliver 25 amps for approximately 100 to 120 minutes before needing to be recharged.
Why Do Amps Ratings Matter In Car Battery?
It’s clear that the amp rating of a car battery can be measured under various battery specifications. The amp-hour (AH) rating indicates how long a car battery will last, while the CCA, CA, and RC ratings indicate how well the battery will perform under various temperatures or weather conditions.
But why are these ratings important?
A typical 12-volt car battery has a capacity of 48 amp-hours. But before you buy a battery, make sure it has enough storage capacity to meet your needs for an extended period. Depending on your vehicle, you may require a 12-volt battery with a storage capacity of 50Ah, 60Ah, or 100Ah.
However, in cold weather, a battery’s storage capacity (or amp-hour rating) has no bearing on how well it can start your car or truck. Depending on the temperature, a battery must deliver a sufficient current to start your car.
To start your car in cold weather, you need a battery with a high Cold Cranking Amps rating of at least 650 CCAs or more. And in warmer or marine conditions, a high Cranking Amp of approximately 750 CA is required to start your car.
Hence, if you drive in a cold climate, you should consider the Cold Cranking Amps rating of a battery before purchasing it, whereas if you drive in a warmer climate, the Cranking Amp rating is more important to you.
Also, knowing your battery’s reserve capacity can help you determine whether the battery is suitable for your vehicle. A high-quality battery should be able to deliver at least 25 amps before the voltage begins to drop. Anything less than this indicates that the battery is of poor quality.
Knowing your battery reserve capacity can keep you from overrunning it and damaging your car engine. You won’t run your car battery for any longer than the time it can sustain its amperage.
How Do You Measure Car Battery Amps?
The simplest way to determine a battery rating is to check the battery’s label. Batteries are typically rated in voltages and amp hours. So, if you see 12V/65Ah on the label, it means the battery has 12 volts and a capacity of 65 amp-hours.
However, the rating on a label does not always reflect the true condition of the battery. As the battery ages, its total capacity decreases, as do its amp hours and ampere rating. To determine the current state of your car battery, use a battery tester or a digital multimeter.
How To Measure Your Battery Amps Using A Multimeter
To determine the amps rating, you must find the battery’s ohm rating on the battery label. Then, calculate the battery amps by dividing the measured voltage by the ohm rating of the car battery.
Here’s how to use a multimeter to measure battery voltage;
Step 1: Set the Multimeter
- Turn off your car’s engine, lights, and other electrical features.
- Set the multimeter to DC to calculate the current voltage of your battery.
- Turn the DCV dial to 20. This enables accurate measurement down to 20 volts.
- Connect the multimeter’s red and black leads to the positive (+) and negative (-) terminals of the battery, respectively.
Step 2: Performing the Test
Once the meter is connected in parallel to the car battery, the reading begins to display automatically.
Take note of the DC volts reading and compare it to the table below, which shows the charge status under no-load:
| Multimeter reading (Volt) | Percent of charge remaining |
| 12.6 | 100% |
| 12.4 | 75% |
| 12.2 | 50% |
| 12 | 25% |
| 11.9 or below | Dead |
Step 3: Check the Result
If the reading is 12.6 volts, then the battery is fully charged. But if it reads 12.4 volts (75% charged or less), it means the battery is undercharged and needs to be recharged.
Simply charge the battery with a battery charger and repeat the test. If the result does not change after recharging, the battery is most likely fading.
However, A battery may measure 12.6 volts, but that doesn’t necessarily mean it’s in good condition. The battery might not produce enough Cold Cranking Amps (CCA) to start the engine, even though the voltage reading is as high as 12.4 volts.
How Do You Test for CCA?
Not every multimeter has the function to read CCA. But if you can get one, it will provide a more accurate reading of your battery’s health.
To test the CCA rating of your car battery on the multimeter,
- Simply connect the positive and negative leads of the multimeter to the appropriate terminals on the battery.
- Then select the read CCA function on the multimeter.
- Start the car engine for about 30 seconds before turning it off.
- Check the CCA readings on your multimeter. Readings should appear on a graph, with a peak and average CCA reading included.
Conclusion
Knowing your battery capacity is important for buying the right replacement battery for your vehicle. And here are a few things to remember:
- The average amp rating of a 12-volt battery is 48Ah.
- A good battery storage capacity can help to run your car engine for a longer period.
- A high Cold Cranking Amp or CA rating is required to start a car in cold or hot weather conditions.
- The battery reverse capacity (RC) rating of your car battery indicates how long it can maintain its amperage.
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