Car batteries power up a number of components in the car. These include headlights, ignition systems, electronic devices like GPS navigation, audio system, and more.
However, the main consumer of a car battery is the ignition system that needs the power in order to start the car. Once the car is running the battery is recharged by the alternator while driving. This is of course different from Electric Vehicles that run entirely from the battery and having power in the battery determines how far the car can run.
A typical car battery is around 50 Ah and this can go higher or lower depending on the size of the car. The battery’s Ah should be indicated on the side of the battery or from the manufacturer’s manual.
Amp-hours of Different Vehicles
Car battery specifications depend on the size of the car and the bigger the vehicle the more power is needed to start it and hence the bigger the battery.
|Type of Car||Amp-Hours||CCA|
|Saloon Car||45 Ah||400 CCA|
|SUV||65 AH||600 CCA|
|Truck||100 Ah||800 CCA|
CCA or Cold Cranking Amps is the amps you can draw from a battery for 30 seconds at 0°F. Cold Cranking Amps describes the ability of the battery to provide strong currents required for starting/cranking of internal combustion engines, usually for 30 seconds,
This is different from Amp Hours (Ah) which describes the capacity of the battery and its ability to provide a certain current.
Cold Cranking Amps (CCA) and Amp Hours (Ah) both describe the capacity of the battery and its ability to provide current for some time.
Converting CCA to Amp-Hours
Conversion between Cold Cranking Amps (CCA) and Amp Hours (Ah) is not a direct one, but CCA is relative to Amp-hours. Bigger batteries will have bigger CCA capacities. But this only applies to starter batteries. They are other types of batteries including deep-cycle and dual-purpose batteries that will not have as high CCA as starter batteries even with bigger capacities.
Battery C Rating
Batteries will be imprinted with numbers like 0.1C, 0.2C, 1C, C10, and so forth. These indicate the C rating of the battery. “C” rating is used as battery power can not be discharged all at once the time is a factor when discharging batteries to ensure safe use.
For example, for a 12V 50Ah battery, C is 50. “1C discharge” means 50A as discharge current. And just like that, 0.1C is 10A, 0.5C is 50A, which equals the number before C multiplied by the C value.
Deep cycle batteries are usually rated at 0.2C and are meant to be discharged over a 20hr period while starter batteries will have a higher rating up to 0.5 C for discharge over 10 hours.
A “C” rating also indicates how a battery should be charged.
How Many Amps to Charge a Car Battery
The maximum recommended rate you can charge a lead-acid battery is 20% of its capacity or 0.5C. This means you can charge a car battery at 10 amps you can go lower even to 1 amp but you should never go higher than 10 amps as this may damage the battery.
Most battery chargers for Car Batteries will have two options 2 amps for a slow charge and 10 amps for quick charging.
Jumpstarters will have more amps as they are meant to kick a battery back to life.
How many Watt-hours in a Car Battery
In order to convert amp-hours to watt-hours, you need to multiply the number of amp-hours by the voltage of the battery. This will give you the number of watt-hours.
So a 50 Amp-hour 12-volt battery will provide around 600 Watt-hours. This is enough to run a 10-watt light bulb for 60 hours.
Using Car Batteries for Energy Storage
Car batteries can be used for energy storage systems. However, they are not the best options you can go for. Car batteries fall under SLI batteries (Start Light Ignite) or starter batteries and are made to provide a burst of power in a short period to start an engine. They are not made for continuous use for a long period of time like deep cycle batteries.
A deep cycle battery can be used continuously for hours and recharged over a fairly short period of time. Car batteries have a large number of thin plates while deep cycle batteries have thicker and fewer plates.
How far to discharge a car battery
Car batteries should be discharged up to 50% of their capacity for short periods of time. If a car battery is discharged more than that it will not last long as it only guarantees up to 300 cycles. To fully discharge a battery counts as 1 cycle.
A deep cycle battery can be discharged up to 90% however for lead-acid batteries it is also recommended to only discharge them up to 50%. However, you can get away with this with lithium-ion batteries.
Lithium Vs AGM
Lithium-ion batteries are better than AGM batteries because they are lighter, have a higher energy density, and can be recharged more quickly. AGM batteries are the more common types of lead-acid batteries used in cars, marine, and RV batteries and fall under deep cycle and starter batteries.
When it comes to lithium-ion batteries they can be used for both as they can be discharged over shorter bursts and can also be discharged over a long period of time. So with lithium-ion batteries, the Ah capacity can vary as manufacturers can provide 1h capacity, some 5h capacity, and some 10h capacity depending on the application of the battery.
How Many Watt-Hours in an Electric Vehicle
Electric Vehicles are rated in Kwh as the batteries operate at high voltage. A typical electric car will be between 30 – 50 Kwh and will use 1Kwh to go for a mile.
Lithium-Ion batteries in EVs use various lithium chemistry combinations to tweak performances. They are designed to provide high energy density while providing high power to weight ratio. Tesla batteries have some additions in their designs to increase the battery’s capacity.
Research and development are still being done to improve these batteries for safer and better performance and also price which we discuss later on.
But generally, Lithium battery technology is truly advanced compared to the older Lead-acid batteries.