How Many Amps is a Car Battery?
Even though we may not know the technical ins and outs of it, we generally all know that our car relies on a battery to work normally. Many of us fear finding our car with a dead or near-depleted battery every day, and we know that in the event of the battery failing or running out of power, our car is essentially useless.
We know that much, but how much detail do we know about our car battery? How many amps is a car battery? What are the important components? How can we better understand the condition of our car battery? The list of questions could go on and on.
To understand the amps in your car battery, we should really try to understand amps themselves.
When you hear the ampere (amp) rating of your car battery, what you are hearing is the electrical storage capacity of that battery. How many amperes in total the battery is rated at depends largely on two factors: the size of the battery, and its internal chemistry.
It gets more technical, however, when you consider that there are two kinds of ampere ratings that you have to take into account:
- Cranking Amps (CA) – also known as Marine Cranking Amps (MCA); shows maximum current that a fully charged battery (usually 12V) can deliver for 30 seconds without dipping below 7.2V in voltage while at 32˚F
- Cold Cranking Amps (CCA) – shows maximum current that charged battery delivers for 30 seconds without dipping below 7.2V in extreme cold (defined as 0˚F)
For reference’s sake, it’s better to work conservatively and consider the CCA rating as the norm, since that gives you a more accurate picture of the battery’s power no matter the outdoor conditions. The usual cranking amps rating of a car is somewhere in between 550 and 1000 amperes. It’s this rating that’s important when you’re wondering about how much power you need to get the car started.
When you’re asking how many amps is a car battery, you can’t ignore the critical unit of ampere-hours (Ah). This unit tells you how long the battery can deliver power before it will have to be charged again. For example, let’s say you have a battery with an Ah rating of 100Ah. This battery is outputting about 10 amps of power each hour, so that means it will last for 10 hours before it needs to be recharged.
How many amps is a car battery in need of?
How many amps your battery has to output depends on many things. One of the biggest driving forces behind creating more powerful and more efficient batteries has been the growth of additional electrical and digital systems within modern cars. Back when cars were mostly analogue, you mostly needed the battery just to get the engine started. Nowadays, however, we need the battery for powering the digital instrument cluster, infotainment and navigation systems, air conditioning and much more. This has led automakers to create more efficient dual-purpose AGM batteries. They’re infinitely superior to traditional flooded batteries, but also more complex.
A good reason to fully understand how many amps your car battery is can be found in the realm of charging. Your car battery will actually be able to sustain itself and charge up in the course of your regular driving as long as you aren’t putting too much strain onto it. This is doubly true when you are driving at speed with high RPMs in the engine. If, on the other hand, you regularly leave your car unused for long periods, or if you accidentally leave on internal lights, a/c or some other system that drains the battery, you’ll need outside charging.
This can be done with a basic battery charger. The most basic model will output about 2 amps of power to your battery per hour. That’s a pretty long charge time overall, very often reaching or exceeding 24 hours, depending on the exact Ah rating. Fear not, however, because you can get chargers with stronger amp ratings such as 4 amps, 10 amps and even more. You have to be careful with fast-charging or more powerful units, however, as they may not be compatible with your home power setup, and may even overload the battery causing further damage.
Always consult with a mechanic if you’re not sure about what kind of charger is best to use.
Bonus: Check our article on How long does it take to charge a car battery!
How do I know if my car has enough charge?
Unlike your smartphone, your car battery can’t display a percentage on its surface. Therefore, before charging up, and to ensure you’ve got enough power after charging, you can use a battery tester or a digital multimeter.
A normal tester will give you the battery ampere rating, and you’ll know where you are. A digital multimeter is a bit different and instead gives you the voltage rating. As you may have noticed, this is not the same as ampere ratings, but it can still tell you if you have a full charge. When you make use of the digital multimeter, it will report a voltage to you, shown by the unit ‘V,’ which you can interpret as follows:
- 12.6V – it’s fully charged
- 12.4-12.5V – it’s about 75% charged
- 12.2V – it’s about 50% charged
- 12V – it’s about 25% charged
- 11.9 or less – it’s dead
What else do I need to know about my car battery’s power rating?
There’s plenty of useful knowledge you can get about your car’s battery without having to get into the level of detail that a mechanic or other specialist might know. Here are some examples of useful facts about your car battery power:
- To start the engine, you’ll need somewhere from about 300 to 500 cranking amps. That should cover any kind of car, including a larger SUV.
- When you’re driving at high RPMs, you might get your battery back to full charge or close within 30 minutes.
- The CCA/CA rating will change over time, steadily reducing as it wears out. Heat and vibrations are two of the biggest causes of damage, plus corrosion.
- Proper battery maintenance and regular checks are, therefore, beneficial.
“How many amps is a car battery?” is an important question to master. It will help you better understand and manage your own car’s battery in a healthy and sustainable way. Stay safe (and charged) on the roads!