8 Lithium Battery Parameters You Should Understand Before Use

Quick Overview: Lithium Battery Parameters

If you’ve ever looked at a battery datasheet and felt overwhelmed by numbers, don’t worry. Below, we’ll go through each of these lithium battery parameters one by one, using plain language and real-world examples, so you can understand what actually matters for your application.

Part 1. Battery capacity (Ah)

Capacity is usually the first parameter people look at, and for good reason. Battery capacity tells you how much electrical charge a battery can deliver under specific conditions. It is measured in ampere-hours (Ah).

Simply put, capacity answers the question:

“How long can this battery power my device?”

For example, a 20Ah battery can theoretically deliver:

• 20A for 1 hour
• 10A for 2 hours
• 5A for 4 hours

In real life, however, capacity is affected by temperature, discharge current, and cut-off voltage. That’s why capacity is often described in more detail.

Types of battery capacity

• Actual capacity

This is the capacity you get under real operating conditions. It is usually lower than the rated value, especially at high discharge currents or low temperatures.

• Theoretical capacity

This represents the maximum possible capacity based on the active materials inside the battery. It assumes ideal conditions and is mainly used for research and comparison, not real applications.

• Rated capacity

This is the nominal capacity specified by the manufacturer, measured under standard test conditions (such as a specific discharge rate and temperature). It’s the value you’ll see on the datasheet.

If you’ve ever noticed your phone battery draining faster in winter, that’s a perfect example of how real-world conditions reduce usable capacity.

Part 2. Energy density (Wh/kg or Wh/L)

While capacity tells you how much charge a battery holds, energy density tells you how much energy it stores relative to its size or weight.

Energy density is usually expressed in:

• Wh/kg (gravimetric energy density)
• Wh/L (volumetric energy density)

This parameter becomes especially important when space or weight is limited, such as in electric vehicles, drones, or portable electronics.

Modern lithium-ion batteries typically offer energy densities in the range of 100–200 Wh/kg. Advanced battery designs aim to exceed 300 Wh/kg, especially for long-range EV applications. However, improvements in energy density happen slowly compared to advances in electronics, which is why battery technology often feels like the bottleneck.

Part 3. Charge and discharge rate (C-rate)

The charge and discharge rate, often expressed as a C-rate, describes how fast a battery can be charged or discharged relative to its capacity.

A 1C rate means the battery is charged or discharged in one hour.

For example:

• A 10Ah battery at 1C delivers 10A
• The same battery at 0.5C delivers 5A
• At 2C, it delivers 20A

High C-rate capability is essential for applications like power tools, electric vehicles, and drones, where short bursts of high current are required.

Manufacturers usually specify:

• continuous charge/discharge rate
• peak or pulse rate, often limited to a few seconds

Respecting these limits is critical for both performance and safety.

Part 4. Voltage (V)

Voltage is one of the most fundamental lithium battery parameters, but it’s also one of the most misunderstood.

In reality, a lithium battery does not have just one voltage value. Instead, several voltage parameters work together:

• Open circuit voltage (OCV)

The voltage measured when the battery is not connected to a load.

• Operating voltage

The voltage when the battery is actually powering a device or being charged. This value changes with load and state of charge.

• Charge cut-off voltage

The maximum voltage allowed during charging. Exceeding this limit can cause permanent damage or serious safety risks.

• Discharge cut-off voltage

The minimum safe voltage during discharge. Going below this limit can shorten battery life or render the battery unusable.

Understanding voltage limits is especially important when configuring battery management systems (BMS).

Part 5. Cycle life and depth of discharge (DoD)

Battery lifespan is usually described using two closely related parameters: cycle life and depth of discharge (DoD).

1 Depth of discharge (DoD)

DoD refers to how much of the battery’s capacity is used in one cycle.

For example:

• Discharging from 100% to 20% equals an 80% DoD
• Discharging from 100% to 50% equals a 50% DoD

In general, shallower discharges significantly extend battery life.

If you want a deeper understanding of how depth of discharge directly affects battery lifespan, this guide on what battery DoD is and how it impacts battery life explains the relationship with clear examples.

2 Cycle life

Cycle life tells you how many charge-discharge cycles a battery can complete before its capacity drops to a defined end-of-life threshold (often 80% of original capacity).

Cycle life is measured under controlled conditions, so real-world results may vary depending on temperature, discharge rate, and charging habits.

3 Calendar life

Calendar life refers to how long a battery lasts over time, even if it’s not heavily used. Storage temperature and state of charge play a major role here, which is why proper storage is so important.

Part 6. Internal resistance (Ω)

Internal resistance represents the opposition to current flow inside the battery. Although it’s often overlooked, it has a major impact on performance.

High internal resistance leads to:

• more heat generation
• lower efficiency
• reduced usable power
• faster aging

Low internal resistance, on the other hand, allows the battery to deliver higher currents with less heat and better overall efficiency. This is especially important in high-power applications.

If you’re curious about how internal resistance is measured and why it changes over time, this detailed article on lithium-ion battery internal resistance breaks it down in a very practical way.

Part 7. Self-discharge rate

Even when a battery is not connected to anything, it slowly loses charge. This is known as self-discharge.

Lithium-ion batteries have relatively low self-discharge rates, usually a few percent per month. However, over long storage periods, self-discharge can still push a battery into over-discharge if it is not periodically recharged.

That’s why long-term storage guidelines often recommend storing lithium batteries at a partial state of charge and checking them regularly.

To learn what causes self-discharge and how fast lithium-ion batteries typically lose charge during storage, you can also read this guide on lithium-ion battery self-discharge rate.

Part 8. Operating temperature range

Temperature has a powerful influence on nearly every lithium battery parameter.

Most lithium-ion batteries are designed to operate between –20°C and 60°C, although the exact range depends on the chemistry. Outside this range, you may see:

• reduced capacity
• increased internal resistance
• limited charge or discharge rates
• accelerated aging

Long-term exposure to extreme temperatures can cause irreversible damage, which is why temperature control is critical in demanding applications.

Part 9. Common lithium battery parameter settings

In real systems, lithium battery settings often include:

• charge cut-off voltage
• discharge cut-off voltage
• maximum charge current
• maximum discharge current
• temperature protection thresholds

These settings are usually managed by a BMS and must match the battery’s design parameters to ensure safety and longevity.

Part 10. Final thoughts

Battery parameters are more than just numbers on a datasheet. They describe how a lithium battery behaves in real life and how well it will fit your application. When you understand these parameters, you can make smarter choices, avoid costly mistakes, and get the best performance and lifespan from your battery.

If you’re working on a project with specific voltage, capacity, size, or performance requirements, a custom lithium battery solution is often the most reliable approach. Choosing the right parameters from the start makes all the difference.