Most batteries are classified based on their voltage. Whether it be a 1.5-volt AA battery, a 12-volt car battery, or a 24-volt deep cycle battery, battery voltage is a relatively common term. Nevertheless, it can be confusing to understand exactly what it means. There are a lot of common misconceptions about voltage. Most of us don’t actually understand how and why it works, let alone if it presents any sort of danger to us.

In this article, we go through everything you need to know about battery voltage, including what it is, how we measure it, and the chemical reactions behind it. Let’s begin.

What Is Battery Voltage?

Battery voltage refers to the difference in charge between the negative and positive terminals. Also known as “electrical potential,” the greater the difference in potential charge, the higher the voltage. Basically, voltage is the pressure pushing electrons from one point to another. 

For example, on the negative end of a battery terminal, there’s an excess of electrons, whereas the positively charged terminal has a lack of electrons. The more electrons that the negative terminal has compared to the positive terminal determines the voltage. 

What Creates Battery Voltage?

Batteries are made of an anode, a cathode, an electrolyte, and a separator. The anode refers to the negative side of the battery and is usually made of zinc, lithium, graphite, or platinum. The cathode, on the other hand, is the positive end of the battery and is usually made of some kind of oxidizing metal, such as lithium oxide, copper oxide, or graphite oxide. 

Because the anode and cathode are separated, electrons can’t freely flow from one side to the other. This is where the circuit comes in. When the battery terminals are connected by a conductor, the electrons can move from the anode to the cathode. This creates voltage. 

Electrons move from the anode to the cathode.

Voltage Versus Current

The difference between battery voltage and current can seem confusing, but it’s actually relatively easy to understand. Volts refer to the potential energy within a battery (thus allowing scientists and manufacturers to match it with an electronic one). Current refers to the rate at which the electrons are flowing. Therefore, we measure the current of electrons in amperes (amps). The higher the amps, the faster the electrons are flowing. 

→ Need more of a refresher? Let’s look at Amps, Volts, and Watts: Difference Explained in Simple Terms

How Do We Measure Battery Voltage?

Measuring battery voltage is important because it allows you to determine the battery’s state of charge. The best way to do this is with either a multimeter or a battery monitor, such as the Victron Energy Battery Monitor BMV-712.

Both of these devices use sensors to measure the electrical potential difference between two points. Then they display that corresponding voltage number on a screen. 

Digital multimeter reading voltage of lithium batteries.
Digital multimeter reading voltage of lithium batteries.

What Is Normal Voltage?

“Normal” voltage completely depends on the type of battery. For example, a car battery will have a different voltage than a household AAA. The reason for differences has to do with the type of chemical reaction within the cell that is creating the voltage. Reactions with more favorability of the oxidation-reduction reaction will produce a higher voltage. Thus batteries of the same chemistry produce the same voltage while different chemistries can produce different voltages.

In addition to the chemical reaction, higher-voltage batteries like a 12V battery have multiple cells in series to increase the voltage. A AAA battery is only one cell, whereas an RV battery is 4 to 6 cells.

This is why the average fully charged car battery will measure around 12.6 volts (also known as the resting voltage). Meanwhile, a AAA battery will only measure about 1.5 volts. They can power electronics with completely different power needs. It’s extremely important to match voltage correctly so as not to damage the electronics or battery itself. 

Lead-Acid Versus Lithium Battery Voltages

The funny thing about battery voltage is that it changes depending on the charge of the battery. At full charge, a battery delivers a higher voltage than when it’s running low or empty. 

But, of course, the voltage loss depends on the type of battery as well. For example, lead-acid batteries tend to experience much larger voltage drops than lithium. This is because of the advanced battery technology that lithium batteries provide. They’re much more energy dense and aren’t as affected by Peukert’s Law

For instance, a 12-volt lead acid battery will deliver about 12.7 volts when fully charged, but only about 11.6 volts at 20% capacity. Meanwhile, a lithium battery will deliver 13.6 volts when fully charged, and 12.9 volts at 20% capacity.

battle born 100 ah lithium battery on table
Lithium batteries will deliver 13.6 volts when fully charged.

Is Battery Voltage Dangerous? 

By OSHA standards, battery voltage isn’t dangerous until it exceeds 50 volts. This is because 50 volts is generally a safe level of shock for the human body, even with unlimited current capacity.

Regulators have based this theory on the power distribution of the human body, which shows the arms and legs to be at least 500 ohms. This means that at 50 volts, a lethal current wouldn’t pass into the trunk and heart, even in the most dangerous circumstances.

However, if the voltage does exceed 50 volts, our bodies can act as a conductor in a way that could be deadly. The dangers of high-voltage electricity (anything over 50 volts) include: burns, broken bones, hearing loss, eye injuries, cardiac arrest, and even death. This is because 10 milliamps through the human heart can disrupt its electrical conductivity, which then can produce a fatal arrhythmia. This is why you should consider all voltage over 50 amps dangerous and why it’s common practice to limit it. 

By and large, battery voltage isn’t dangerous. It’s more the current that is dangerous, rather than the voltage itself. Remember, voltage simply measures the pressure moving electrons from one place to another. So it’s mostly a matter of whether that “pressure” is high enough to push the current into your body.

Why Does Battery Voltage Matter?

Battery voltage matters for a variety of reasons. Namely, it allows you to determine how much power your battery is capable of supplying, how much voltage you need for certain electronics, and even the charge state. Without the ability to measure battery voltage, we would have no way of safely using batteries — and therefore no batteries to use! 

Do you have any questions? Leave them in the comments below!

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