How Many Amps is a Car Battery - Car Battery Amps?
Knowing your car's battery amps and other features is very important not only when replacing the battery, but also when the battery is being used not only for cranking purposes but also for powering other electric and electronic systems like lights, navigation, multimedia devices, security systems, etc.
With more and more onboard systems, car manufacturers are slowly replacing pure starting batteries with the new dual-purpose AGM batteries, featuring many improvements over older flooded ones.
Updated: January 14, 2022.
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Car Battery Features and Specifications
In order to understand what your car's battery can and what cannot do, it is important to know several battery details, like chemistry, voltage, capacity (Ah), Reserve Capacity, CCA (Cold Cranking Amps), MCA/CA (Marine Cranking Amps/Cranking Amps), HCA (Hot Cranking Amps), PHCA (Pulse Hot Cranking Amps), etc.:
- Chemistry: most car batteries are tested and reliable lead-acid batteries, but wet/flooded lead-acid batteries are being replaced by Absorbent Glass Mat (AGM) Sealed Lead Acid (SLA) batteries, offering greater vibration resistance, spill-proof design, maintenance-free operation, and similar.
Lithium-ion drop-in replacements are available as both starting and dual-purpose batteries, but such batteries are not as nearly tested in real-life situations as AGM SLA batteries.
- Voltage: lead-acid car batteries feature a nominal voltage of 12 volts, while the actual voltage is different. When the engine is running and the alternator charges the battery, the common voltage is in the 13.5 - 14.0 volts range and it should never be above 15 volts. When the engine is not working, the voltage of the fully charged AGM battery should be in the 13+ volts range - actual voltage may depend on the exact battery model and the onboard electronic system being constantly online. If the battery voltage drops below 10.8 volts (1.80 volts per cell) and the engine is not working, the battery is deeply discharged.
- Capacity of the car batteries is given is Amps Hours (Ah) and it describes how many Amps (A) batteries can provide for 20 hours, before the voltage drops below a certain level, usually down to 10.5-10.8 volts (1.75-1.80 volts per cell). Draining the battery below this cut-off voltage may cause permanent damage to the battery
For example, the capacity of lead-acid batteries is determined by how many amps of current can new, fully charged 12V battery at 80°F (~25°C), deliver for 20 hours without its voltage falling below 10.5V.
Typical car batteries feature nominal capacity in the 50-100 Ah range, with large diesel-powered trucks often having 100+ Ah batteries being able to provide 1000+ CCA.
Note: Yugo 45 with its 'lawn mower engine' had a 34 Ah starting battery, which was able to start the engine with ease. If the engine wanted to start, of course :)
- Reserve Capacity (RC) is the number of minutes that a new, fully charged battery (at 80°F, ~25°C) can deliver a 25A current and maintain a voltage above its cut-off value (10.5V for lead-acid batteries).
Although RC value is more important for deep cycle batteries used in marine applications (for trolling motors, for example), RVs (in-house batteries), solar systems (off-the-grid applications), UPS (Uninterruptible Power Systems), and similar, Reserve Capacity is getting more and more important for car batteries as well.
For example, when the engine is off, multimedia systems may drain battery with relatively strong currents - 200 watts multimedia system may draw 20-25 Amps from the battery with ease (in some cases even more).
For even stronger multimedia systems, electric systems with two separate batteries are recommended - one as a starting battery, another battery for multimedia, and other systems.
- Cold Cranking Amps (CCA) is the value of the maximum current that a new, fully charged, 12V battery can deliver for 30 seconds, with the voltage NOT dropping below 7.2V, at 0°F (-18°C).
Cold Cranking Amps (CCA) is a very important value for cars, trucks, and other vehicles during winter and is often the first one to look for when checking the starting batteries.
- CA (Cranking Amps) or MCA (Marine Cranking Amps) is the value of the maximum current that a new, fully charged, 12V battery can deliver for 30 seconds, with the voltage NOT dropping below 7.2V at 32°F (0°C).
CA/MCA value shows how good is the battery for marine cranking/starting applications where actual battery temperatures rarely drop below 32°F (0°C).
Note: Although 30 seconds appear too long for starting applications regardless of whether it is CCA or CA/MCA, note that this is the value for the brand new, fully charged battery. In real life, the battery must perform properly even after being used for some time (months and years) and without being fully charged!
- Hot Cranking Amps (HCA) is the value of the maximum current that a new, fully charged, 12V battery can deliver for 30 seconds, with the voltage NOT dropping below 7.2V, at 80°F (27°C). Note that some manufacturers provide PHA values measured at other temperatures.
Since the HCA value is ~1.6-1.7x larger than CCA for most AGM batteries, the most important value for measuring the strength of the battery is CCA, even if the battery is not intended for low-temperature applications.
- Pulse Hot Cranking Amps (PHCA) is the value of the maximum allowed current that a new, fully charged battery may provide for 3-5 seconds at 77-80°F (25-27°C). This is a rather 'unofficial' parameter, but nonetheless, often used to measure starting strength of the battery.
Similar to PHCA, some manufacturers provide values for 'maximum pulse drain current' and are often given in Amps and seconds, for example, 200 Amps for 10 seconds, 100 Amps for 15 seconds, and similar.
- Maximum charging current is the allowed maximum current that can be used for charging the battery without damaging the battery. Personally, discharged AGM batteries should be regularly charged for 2+ hours, while quick charging (less than 1 hour) should be used only when absolutely needed, even when quick charging batteries are being used. Call me paranoid, but ...
As one can see, a simple car battery is not just a battery and knowing its voltage and capacity is not enough to determine if the battery is well suited for a specific car or not.
Frequently Asked Questions (FAQ)
Here are some of the most common Frequently Asked Questions about car batteries, their voltages, wattages, Amps, and similar:
Are car batteries 12V or 24V?
Most cars feature 12V electric systems, meaning that their batteries have a nominal voltage of 12V.
Are there 24V car batteries?
For cars, SUVs, trucks, boats, yachts, and industrial applications that require 24V batteries, 24V batteries are used:
- two very same lead-acid batteries are connected in series in order to create a 24V battery pack,
- two very same lithium starting batteries are connected in series in order to create a 24V battery pack,
- one 24V lithium starting battery.
Note: lithium batteries should be connected in series and/or parallel only if explicitly allowed by their manufacturers.
Can a car battery go dead from sitting? How long can a car sit before the battery dies?
Yes, even if the battery is disconnected from the car's electric system, it can go dead after some time.
Batteries have a certain self-discharge rate, which is increased during warm days.
What is the life expectancy of a car battery?
Typical car battery lasts 3-4 years, although in certain situations (hot climate) the battery can last much shorter.
If the car is regularly driven and protected from extreme temperatures, the battery can last 4-5 or even more years.
How do I know when my car needs a new battery?
If the lights are dimmer, if the car doesn't start easily, if the Stop&Go system is automatically turned Off, or if the car dashboard simply says "Weak battery" or "Replace the battery"...
How long does it take to charge a car battery with a 6 Amp charger?
It all depends on the amount of charge that has to be transferred to the battery.
For example, if the 75Ah battery is discharged down to 50% DoD, it requires 37.5Ah to be fully recharged.
Theoretically, a 6 Amps car battery charger may charge the required 37.5Ah in 6.25 hours, but since the batteries are not ideal batteries, in real life it will take 7-8 hours to recharge such battery.
How long does it take for a car battery to drain if lights are left on? How long does a car battery last if interior lights are left on?
It all depends on the car battery capacity and the wattage of the lights.
If the car has a 75Ah battery and the headlights draw 10 Amps, it will take ~7 hours to fully discharge the battery.
However, if the headlights are LED lights that draw 3-4 Amps, it will take much longer - in order to accurately calculate lights runtime, check the capacity of the car's battery and the headlights wattage/Amps.
Similarly, check the wattage/Amps of the interior lights and do the math...
How long does it take to charge a car battery from another car?
When jumpstarting the car, it is recommended to have the cars connected for a few minutes first in order to transfer some charge to the discharged battery and to create a so-called "surface charge" that will aid in cranking the engine.
However, to charge the discharged battery using another car, it takes at least 30 minutes to transfer enough charge to consider the discharged battery at least somewhat capable of cranking the engine - it is still far from being charged.
Note: when one car is being used to charge the battery of another car, its alternator and charging controller are under a large load - if possible, crank the engine after a few minutes and disconnect the vehicles ...
How long do you have to drive a car to charge the battery?
After jumpstarting the car, it takes at least 30 minutes to somewhat recharge the battery and at least one hour to consider the battery charged enough to be able to crank the engine without issues next time.
But, this is highly individual...
Long Story Short: if you wonder 'How Many Amps is a Car Battery', check its specifications including chemistry and type, capacity, CCA, battery size, terminal type and orientation, and similar. If you know these values, You practically know everything that is needed to get your battery replacement.
Other values like MCA, HCA, PHCA, RC, maximum drain currents, and similar are nice to know, but not absolutely needed unless some specific requirements must be met by the car battery.