Battery Voltage Explained: What You Need to Know

What Is Battery Voltage?

A battery’s voltage is the difference between its positive and negative terminals. Also referred to as “electrical potential,” the greater the difference in potential charge, the higher the voltage. Basically, voltage is the force that pushes electrons from one point to another.
The voltage of a battery is determined by how many electrons are present on the negative terminal compared to the positive terminal.

What Creates Battery Voltage?

Battery components include an anode, a cathode, an electrolyte, and a separator. The anode is usually zinc, lithium, graphite, or platinum, and refers to the battery’s negative side. On the other hand, the cathode is the positive end of the battery and usually consists of oxidizing metals like lithium oxide, copper oxide, or graphite oxide.
When the battery terminals are connected by a conductor, electrons can freely flow between the anode and cathode. This creates voltage since electrons can’t freely flow between the two sides.

Voltage Versus Current

Despite the confusion, it’s relatively easy to figure out the difference between battery voltage and current. A battery’s voltage refers to its potential energy, so scientists and manufacturers can match it to a computer. As electrons flow at a particular rate, current is measured in amperes (amps). The higher the ampere, the faster the electrons flow.

How Do We Measure Battery Voltage?

You can measure battery voltage using either a multimeter or a battery monitor, such as the Victron Energy Battery Monitor BMV-712.
They both use sensors to measure the electrical potential difference between two points. The corresponding voltage number is displayed on the screen.

What Is Normal Voltage?

Different batteries have different “normal” voltages. For example, a car battery has a different voltage from a household AAA battery. This is because of the chemical reaction taking place in the cell. A higher voltage is produced by oxidation-reduction reactions with greater favorability. A battery of the same chemistry will produce the same voltage, while a battery of a different chemistry will produce a different voltage.
Additionally, higher-voltage batteries have multiple cells in series to increase their voltage. AAA batteries have only one cell, while RV batteries have four to six cells.
The average fully charged car battery (also known as the resting voltage) measures around 12.6 volts. While AAA batteries have a voltage of about 1.5 volts, they can power electronics that require completely different levels of power. To prevent damage to the electronics or battery, it is extremely important to match voltage correctly.

Lead-Acid Versus Lithium Battery Voltages

When a battery is fully charged, it delivers a higher voltage than when it’s empty or low on charge.
There are, however, differences in voltage loss based on the type of battery. As a result of lithium batteries’ advanced technology, they are much more energy dense and aren’t as affected by Peukert’s Law as lead-acid batteries. For example, lead-acid batteries tend to experience much bigger voltage drops than lithium batteries.
As an example, a 12-volt lead acid battery will deliver about 12.7 volts when fully charged, but only about 11.6 volts at 20%. By contrast, a lithium battery will deliver 13.6 volts when fully charged, and 12.9 volts at 20%.

Is Battery Voltage Dangerous?

According to OSHA standards, battery voltage doesn’t become dangerous until it exceeds 50 volts, because even with unlimited current, 50 volts is a safe level of shock for the human body.
In order for this theory to work, regulators have based it on the power distribution of the human body, which indicates that the arms and legs are at least 500 ohms. This means that, even in the most extreme circumstances, a lethal current wouldn’t pass into the trunk and heart.
If the voltage exceeds 50 volts, it can be deadly as our bodies act as a conductor. The risks of high-voltage electricity include burning, broken bones, hearing loss, eye injuries, cardiac arrest and even death. That is because 10 milliamps in the human heart can stop its normal electrical conductivity and trigger a fatal irregular heartbeat. It is prudent to limit this voltage for safety purposes.
Voltage is not dangerous, in general. It’s more the current that’s dangerous, rather than the voltage itself. Remember, voltage measures the pressure required to move electrons from one place to another. If that “pressure” is high enough, the current will flow into your body.

Why Does Battery Voltage Matter?

You can use battery voltage to determine the amount of power your battery is capable of supplying, how much voltage you need for certain electronics, and even the charge state of your battery. Without the ability to measure battery voltage, we would be unable to safely use batteries — so we wouldn’t be able to use batteries.