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.
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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 nominal voltage of 12 volts, while actual voltage is different. When the engine is running and the alternator charges the battery, 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, voltage of the fully charge AGM battery should be in the 13+ volts - actual voltage may depend on the battery and onboard electronic system being constantly online. If the battery voltage drops below 10.8 volts (1.80 volts per cell) and engine is not working, battery is deeply discharged.
- Capacity: capacity of the car batteries is given is Amps Hours (Ah) and it describes how many Amps (A) battery can provide for 20 hours, before the voltage drops below 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 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 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 number of minutes that a new, fully charged battery (at 80°F, ~25°C) can deliver 25A current and maintain 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 very important value for cars, trucks and other vehicles during winter and is often 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 drops below 32°F (0°C).
Note: Although 30 seconds appear too long for starting applications regardless if it is CCA or CA/MCA, note that this is the value for the brand new, fully charged battery. In real life, 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 value measured at other temperatures.
Since 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 charge battery may provide for 3-5 seconds at 77-80°F (25-27°C). This is 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 is 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 ...
Long Story Short: if you wander 'How Many Amps is a Car Battery', check its specifications in this order: chemistry and type, capacity, and CCA. If you know these three values, you practically now everything what 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.
And don't forget the size of the battery, just in case ...