An automotive battery is a crucial part of a car’s mechanism. The battery provides the energy to start the engine and power electrical components.
Depending on the car types and functionality, each car has distinct battery specifications to meet its energy needs.
For example, you need 12-volt batteries to power your traditional internal combustion engine (ICE) vehicle to ignite the engine and power the electrical components, including the lights.
On the other hand, electric vehicles (EVs) are equipped with a different set of batteries with voltage ratings ranging from 400V to 800V. High-voltage batteries in this range are needed to supply an EV with adequate battery juice to meet the energy demands of the car.
Voltage Levels of A 12V Lead Acid Automotive Battery
A regular automotive battery is rated at 12V, but it operates on different voltages depending on the car’s demand, most influenced by the car’s mechanical and electrical system. Here is a guide to how an automotive battery’s voltages vary based on operational needs.
Resting voltage
The resting voltage defines the state of a battery when it is not functioning, such that there is no charging process or any load on the battery. This is when the car and the electrical system are not working and are “resting.” During rest, the battery maintains a voltage of 12.6–12.8V.
Cranking Voltage
The starter motor needs a power from the battery for the engine to start. At this point, also known as engine starts, where the engine supplies power to ignite the engine, a noticeable drop of voltage is noticed, dropping the battery’s voltage to about 9 to 10 volts.
However, the battery recovers to its original voltage of 12 volts once the engine starts.
Charging Voltage
After the battery has supplied power to the starter motor and the engine is running, the alternator is triggered to run and charge the battery.
This increases the battery voltage to about 13.7 to 14.7 volts, mostly depending on the status of the car’s electrical system and the battery’s charging status. With the raised voltage level, the battery can power all the electrical components connected to the car.
Under Load
Once the alternator starts charging the battery and you engage your car’s electrical accessories, such as the audio system, air conditioning, and lights, the battery witnesses another round of voltage drop.
While the voltage drop depends on the voltage demands of the accessories running, it usually stays between 12 to 14.7 volts. Regardless, the alternator continues to charge the battery to compensate for the electrical load.
Undercharging
Undercharging occurs when a battery’s voltage drops below 12 volts, and a failing alternator is the common culprit. When this happens, it means the alternator fails at its duty of charging the battery with no compensation for the energy drawn by the electrical accessories in the car.
However, it is also worth noting that a faulty electrical system can result in undercharging.
Overcharging
A car battery not only experiences undercharging but also can go through overcharging. Overcharging occurs when the battery charges beyond the regulated voltage, commonly 15 volts. This phenomenon is linked to a malfunctioning alternator or voltage regulator.
Regardless, it is important to note that the voltages highlighted are peculiar only to 12V lead-acid batteries. Hybrid and electric vehicles come with higher voltage batteries with different battery ranges and operational demands.
The 12V battery connected to a traditional internal combustion engine is necessary for starting the engine and powering the electrical system. This battery has become a standard in the automotive industry due to its reliability, simplicity, and cost-effectiveness.
The only challenge with 12V batteries is the limited capacity to support the electrical demands of modern vehicles. Modern vehicles like hybrid and electric vehicles depend on high-voltage batteries as their power source.
Car Battery Voltages of Hybrid Vehicles
Hybrid vehicles feature a combo of an internal combustion engine (ICE) and an electric motor connected to a battery. Although the battery voltages in hybrid vehicles vary, they are lower than those in fully electric vehicles.
It is also worth noting that the battery voltage in hybrid cars depends on the vehicle models and the hybrid system.
Types of Hybrid Vehicles and Their Battery Voltages
Again, hybrid vehicles are available in different systems, and each system’s battery voltage is unique. Here are classes of hybrid vehicles and their properties:
Mild Hybrid Electric Vehicles (MHEVs)
The mild hybrid electric vehicle features a 48V battery, and the Audi A6 55 TFSI is a popular reference.
MHEVs use a 48V lithium-ion battery combined with an integrated starter generator. The battery complements the ICE and caters to specific car functions, such as regenerative braking, start-stop functions, and power assist. This ultimately improves fuel efficiency but doesn’t equate to pure electric driving.
Full Hybrid Electric Vehicles (FHEVs)
The Toyota Prius is a common car model with a full hybrid system. FHEVs feature a higher battery voltage than their MHEV counterparts. The battery voltages in FHEVs range from 200-300V.
While Some FHEVs use nickel-metal hydride (NiMH), while others adopt lithium-ion for higher energy density. to hold sufficient energy for short-distance pure electric driving.
The full hybrid electric system is more fuel-economical than the mild hybrid system and hence has lower emissions. The vehicle can drive short distances with just the battery, so the ICE can rest and perform better when engaged.
Check out our EV Battery Test System.
Plug-in Hybrid Electric Vehicles (PHEVs)
Plug-in hybrid electric vehicles are powered by high-capacity lithium-ion batteries, as evident in the BMW 330e and Chevrolet Volt. The system is equipped with an onboard charger for external electricity input. Thanks to the higher-capacity batteries, PHEVs can travel long distances relying only on electric power. This means more fuel economy and lower emissions.
Also, the higher-voltage batteries in the plug-in hybrid vehicles enable them to accelerate more with better overall performance.
Interpretation of Different Battery Voltages in Hybrid Vehicles
While the lower voltage batteries associated with mild hybrid vehicles mean limited dependence on electric functionality, the battery is still enough to provide power assistance and offer reduced fuel consumption.
On the other hand, full hybrids and PHEVs are better options for fuel economy and lower emissions. The batteries in these systems support temporary independence from the ICE and drive mainly on the battery. This offers more fuel economy and further reduces emissions.
Possibilities of Electric-Only Driving
Since mild hybrid vehicles are only equipped with low-voltage batteries, they lack the possibility of electric driving. They rely on the ICE for their driving needs. They only need the low-voltage battery for enhanced electrical functionalities.
You can only expect electric driving with full hybrid and plug-in hybrid electric systems, thanks to their higher-capacity batteries. The batteries afford them the capacity to drive mainly electric. However, it is worth noting that while the PHEV system can drive for significant distances (typically 20-50 miles), the full hybrid system can only cover very short distances (1-2 miles) on electric power.”
Charging Requirements
The plug-in system charges its higher-capacity battery from an external charging unit, primarily using AC charging which requires several hours for a full charge. Most PHEVs do not support DC fast charging, unlike fully electric vehicles, the plug-in hybrid with higher voltages requires an external charging unit to charge.
The mild and full hybrid system rely on the ICE and regenerative braking to recharge the battery, but the full hybrid system draws more of its juice from regenerative braking due to higher voltages.
The plug-in system charges its higher-capacity battery from an external charging unit and supports fast charging.
Cost and Complexity
Due to their limitations and less complexity, mild hybrid vehicles are less expensive than their full hybrid and plug-in hybrid counterparts.
Full hybrids are a more complex and expensive option than the mild hybrid system, mainly because of higher voltage requirements and advanced battery management systems.
PHEVs are the most expensive hybrid systems in the lineup. The high cost is credited to the complexity of the vehicles, such as high voltage, larger batteries, and additional requirements for external charging.
Battery Voltages in Electric Vehicles (EVs)
Unlike hybrid vehicles that rely on ICE and batteries to power their powertrain, EVs rely mainly on high-voltage batteries for electrical energy to power their motors. Most electric car models also come with low-voltage batteries that power auxiliary functions. This helps ensure that each section of the car gets the required amount of voltage for enhanced efficiency.
High Voltage Battery Packs
Again, the high-voltage battery system in EVs provides power for propulsion and can range from 200 to 800 volts, depending on factors like performance requirements and models.
For example, while the Nissan Leaf operates on a 360V battery pack, the Tesla Model S is powered by a 400V battery pack, and the Porsche Taycan is equipped with an 800V power system.
Check out our High-Volt Storage Battery Cluster.
Components of EVs and Their Functions
The EV power system comprises a couple of components, with each one assigned to specific tasks.
Battery Pack: The battery pack is where the energy emanates and is composed of a couple of lithium-ion cells with the capacity to provide the adequate voltage level required for the vehicle’s operation. The batteries can be arranged in series or parallel based on the requirements.
Inverter: The inverter takes the DC power supplied by the battery and converts it to AC, which is then sent to the electric motor.
Electric Motor: The electric motor is powered by AC power from the inverters and is used to propel the EV. Electric motor: Powered directly by the high-voltage battery pack.
Onboard Charger: The power from the charging station is an alternating current, but the battery pack can only store direct current. An onboard charger is a prominent component of an EV as it helps convert alternating current (AC) from the charging station to direct current (DC).
Impact of High-Voltage Batteries on Performance
High Efficiency: The most important benefit of a high-voltage battery pack in EVs is high efficiency. The high voltage helps reduce current, which is necessary to reduce losses due to resistance. The higher the voltage, the more power that reaches the motor, and the higher the car’s performance.
Improved Charging speed: Electric vehicles utilize high-voltage battery systems to foster faster charging. With the battery able to accommodate high voltage, the battery can be connected to fast-charging outlets. For example, thanks to ultra-fast DC chargers, the Porsche Taycan with an 800V system takes less time to charge compared to the Tesla Model S, which is connected to a 400V battery pack.
More acceleration: With high voltage, the battery can send enough power needed to propel the powertrain of the car at higher speeds. Hence, the high-voltage battery system contributes to enhanced acceleration and overall performance of an EV system.
Check out our High-Performance EV Battery Test System.
Low Voltage Auxiliary Systems
Remember that most EV models come with low-voltage batteries that power additional vehicle accessories.
These batteries range from 12V to 48V, depending on the requirements for the additional accessories. For example, the 12V battery is used in models where only regular automotive components are powered, while the 48V systems are seen in models with demanding electrical loads, especially in modern EVs.
Components and Functions
Battery: The auxiliary battery, which can be a lead-acid or lithium-ion battery, handles the infotainment, power windows, lights, and other accessories.
DC-DC Converter: Although the current needed to charge the auxiliary battery is also in DC with the high-voltage battery pack, the voltage needs to be stepped down. This is where the DC-DC comes in. The converter steps down direct current from the high-voltage battery to charge the low-voltage auxiliary battery.
Electrical Systems: the electric systems draw power from the auxiliary battery system rather than the high-voltage battery pack. The electrical systems include the infotainment, lighting, and safety systems.
Impact of Auxiliary Batteries on EVs
The auxiliary battery ensures that auxiliary accessories of an EV are supplied with the right voltage without depending on the high-voltage battery. This means the car’s accessories will continue functioning even when the higher-voltage battery system fails.
What Factors Affecting the Automotive Battery Voltage
A few factors can influence the voltage and overall performance of an automotive battery. Factors like temperature, age, and maintenance pattern all contribute to what to expect from your automotive battery’s voltage.
Temperature
While highly cold temperatures can limit the battery’s ability to hold a charge, high temperatures are linked to accelerated chemical reactions in batteries, a major cause of battery degradation.
Age
On the age front, automotive batteries drop in performance with age. With continuous use, a battery’s internal components naturally wear and tear, reducing its capacity to hold a charge.
Maintenance
The maintenance pattern of an automotive battery is more than cleaning the battery. It also includes how the battery is used.
For example, when electrical accessories are left on when the engine is off, the battery is drained, and voltage drops are witnessed. Also, when the battery is used only for short periods, it lacks the time to attain full charge.
Contact us at Sinexcel-Re for your battery testing solutions.