If you're learning about the world of batteries, you've more than likely come across the term "nominal voltage." Don't be intimidated by its technical-sounding name; it's a fundamental concept that's super easy to grasp. In fact, it was designed to make batteries easier to understand for consumers.
Nominal voltage is a term designed to simplify understanding for consumers and ensure compatibility between devices and power sources. It represents the average voltage that a battery maintains throughout its discharge cycle, providing a useful reference point for the battery's operational range. This single value helps consumers and engineers easily compare and select batteries for their devices without needing to understand the entire discharge curve.
The importance of nominal voltage extends to the design and standardization of electrical systems. Engineers rely on this value to choose components that operate efficiently within a specified voltage range, minimizing risks of overvoltage or undervoltage that could damage devices or reduce performance. Additionally, nominal voltage facilitates the creation of universally compatible batteries and electrical components, allowing consumers to confidently purchase batteries for their devices. This standardization is crucial for applications ranging from small electronics to electric vehicles and solar power systems, where precise voltage levels are needed to ensure optimal operation and safety. Understanding nominal voltage enables better design, compatibility, and efficiency in battery-powered systems.
In this article, we will explain what nominal voltage is, how it can be used, and why the concept of a normal voltage is important. We will also go over nominal voltage for common cell chemistries.
What Does Nominal Voltage Mean?
Nominal voltage essentially means ‘the average voltage’ that a battery will be over any given discharge cycle. It’s basically a convenient compromise. Knowing what nominal voltage is lets you determine if a given battery will work with a given device without having to plot the entire discharge curve. This single figure is much easier for the average consumer to deal with when comparing battery-operated systems to the batteries that will be used to operate them.
Nominal voltage is used because it’s simply a lot easier to grasp a single voltage rather than a range of voltages. The actual voltage of a battery can fluctuate due to various factors such as its current state of charge, the amount of current being drawn from it, the ambient temperature, and the battery’s age.
A battery's voltage will have a voltage that is higher than its nominal voltage when it’s fully charged, and then as it discharges, the voltage will drop, eventually dipping well below the nominal value before the battery is considered dead. This fully charged voltage and discharged voltages for a given battery pack vary based on the type of chemistry, but the most common type of 18650 cell has a min voltage of 2.5 and a max voltage of 4.2 because it uses NMC chemistry.
For example, a 12-volt 3S (three cell groups in series) NMC lithium-ion battery's voltage when fully charged is 12.6 volts. It will drop to well within the 11-volt range as it's being discharged because it has a nominal voltage of around 10.8V. We still refer to it as a 12-volt battery because when using NMC cells, 3 cells in series is as close as you can get to a 12V lead acid battery voltage range.
While nominal voltage might seem like an annoying oversimplification, it turns out to be a handy way to understand a battery's operating range without getting bogged down in the details.
Why's Nominal Voltage Important?
Nominal voltage serves as a dependable reference point. Imagine your gadget requires 12 volts to operate. If you know the nominal voltage of your battery, you can easily calculate how many batteries you need to connect in series to achieve that precise voltage level.
Nominal voltage is not useful only for the consumer. In fact, the concept of a nominal voltage simplifies the design process of electrical systems. Engineers and technicians can select components that are compatible with the nominal voltage, thus ensuring that each part functions within its intended voltage range. This reduces the amount of work required to find parts that are compatible with a given project.
Also, a nominal voltage is vital for the standardization of electrical components and appliances. It allows manufacturers to produce batteries, devices, and other electrical components that are universally compatible with standard systems. This standardization is what enables consumers to purchase a battery or device and confidently expect them to work together.
How Nominal Voltage Affects Battery Packs
Remember that when you're using multiple batteries together, such as in a DIY portable power station or an electric vehicle, the nominal voltage of the entire battery pack is what matters. This collective voltage depends on the number of batteries you have and how they are connected.
Nominal voltage gives us a baseline understanding of a battery's performance under typical conditions. It's like the average temperature of a city over a year – it tells you what to expect, but the actual daily temperature is almost certainly going to be something different.
When designing a battery pack, the nominal voltage is a key factor to consider, especially when the application requires a specific voltage to operate efficiently. The nominal voltage is determined by the voltage of individual cells and how they are connected. For example, if each NMC (Nickel Manganese Cobalt) lithium-ion cell has a nominal voltage of 3.7V, then connecting them in series will sum their voltages. In a scenario where you need a 48V battery pack, you would need to connect 13 cells in series (13 cells x 3.7V per cell = 48V). This is a common setup for light electric vehicles, such as e-bike battery packs, which often operate at a nominal 48V.
For more demanding applications, such as larger electric vehicles or more robust portable power stations, a higher nominal voltage is often required. To achieve a 72V nominal voltage, you would need to connect 20 NMC lithium-ion cells in series (20 cells x 3.6V per cell = 72V). This higher voltage can provide increased power and efficiency for the system it's designed to run. It's important to note that the battery management system (BMS) is essential in both cases, as it ensures that the battery pack operates within safe parameters, maintaining the longevity and safety of the pack. The BMS will manage the charging and discharging of the cells to prevent overcharging or deep discharging, which can be harmful to the battery's health. Furthermore, the BMS will work to keep the battery in balance to help extend the pack's life.
Charging and Discharging: During charging, the voltage of a battery increases, often exceeding the nominal voltage. Similarly, when discharging, the voltage drops below this level.
Battery Chemistry: Different battery chemistries have different nominal voltages. For example, a standard lead-acid battery typically has a nominal voltage of 2 volts per cell, while a nickel-cadmium (NiCd) cell has a nominal voltage of 1.2 volts.
Real-World Examples of Nominal Voltage in Action
Electric Vehicles (EVs): EVs use large battery packs. Let's say each cell has a nominal voltage of 3.7 volts (common for lithium-ion cells). If an EV requires a 400-volt battery pack, you would need about 112 cells in series (400 volts / 3.7 volts per cell). This series configuration increases the voltage to meet the vehicle's requirements.
Portable Power Stations: These often use lithium-ion (NMC) or lithium-iron phosphate (LiFePO4) batteries. For a power station with a nominal voltage of 24 volts, if using LiFePO4 cells with a nominal voltage of 3.2 volts, you'd need 8 cells in series (24 volts / 3.2 volts per cell). In contrast, using NMC cells requires just 7 cells in series to be considered a 24V battery. This is due to its higher 3.6 volt nominal voltage.
Solar Power Storage: In a DIY solar power system, batteries store the energy collected by solar panels. If the system is designed for 48 volts, and you're using 12-volt AGM (Absorbent Glass Mat) batteries, you would need four of these batteries in series to achieve the required voltage. In this case, the actual voltage is going to be way higher or way lower than 48 volts because 48 volts is just the normal voltage of this particular system.
Nominal Battery Voltage By Cell Chemistry
Each type of battery chemistry has its own nominal voltage, which is essentially the average voltage a battery maintains during most of its discharge cycle. So, it’s important to consider this when you are working with a given battery.
Keep in mind the numbers below are single-cell nominal voltage. So a battery with 13 cells in series would be 13 times the nominal voltage of one cell to give you a pack nominal voltage.
Here is a handy list of nominal voltages for the most common cell chemistries:
Understanding nominal voltage is a key to unlocking the mysteries of battery technology, whether you’re a consumer selecting the right power source for your devices or an engineer designing complex electrical systems. Nominal voltage is a simplified yet crucial concept that not only streamlines the comparison and selection process but also ensures compatibility and efficiency across a wide range of applications, from everyday electronics to electric vehicles and solar power systems.
By focusing on the nominal voltage, you can confidently navigate the world of batteries, ensuring that your devices operate safely and effectively. Embrace the simplicity and power of nominal voltage to enhance your knowledge and make informed decisions in the ever-evolving landscape of battery-powered technology. Thank you for reading and empowering yourself with this essential insight into the world of batteries!
We hope this article told you everything you needed to know about nominal voltages, thanks for reading!
