18650 Battery Pack Calculator - DNK Power

People want a fast calculator to help on their custom battery design, however, since things are complicated with different voltage and capacity of each cell, we think people designing the battery packs should know some basics of lithium battery design.

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Battery packs achieve the desired operating voltage（ie: Total Battery Pack Voltage） by connecting several cells in series( S in short ); each cell adds its voltage. Parallel( P in short) connection attains higher capacity by adding up the total ampere-hour (Ah).

to help you further understand how it works, see below explanation:

#1 For the series connection, batteries with same(almost) voltage and capacity are connected to raise the voltage of final battery packs. The positive terminal of the first battery is connected to the negative terminal of a second battery and so on until the desired voltage is reached. The final voltage is the amount of all battery voltages added together while the final capacity(Ah) remains unchanged.

#2 While for parallel connection, batteries with same(almost) voltages and capacities are connected together to increase the capacity of the overall battery pack. The positive terminals of all batteries are connected together, or to a common conductor, and all negative terminals are connected in the same kinds. The final voltage remains unchanged whilst the capacity of the assembly is the sum of all individual cells together for such parallel design.

let’s use Samsung 3.7V 2.6Ah( mAh) for example.

1S1P pack that’s 3.7V 2.6Ah battery pack

2S1P pack that’s 7.4V 2.6Ah battery pack

1S2P pack that’s 3.7V 5.2Ah battery pack

2S2P pack that’s 7.4V 5.2Ah battery pack

Many battery packs may consist of a combination of series(S) and parallel(P) connections.

For Laptop batteries with 11.1V 4.8Ah battery pack, it commonly has three 3.7V battery cells in series (3S) to achieve a nominal 11.1 V rechargeable battery and two in parallel(2P) to boost the capacity from 2.4Ah to 4.8Ah. As you can find it will be a configuration is called 3S2P, meaning three cells in Series and two in Parallel.

When size limitation was considered, there is much more we need to consider, see below picture.

Stop here and check if you can figure them out.
and here is the answer:

very easy, don’t you?

Let’s now calculate another 11.1V 100Ah battery pack, let’s see how many cells would be needed: 11.1V/3.7V=3, so that’s 3S 100Ah/2.6Ah=38.5 so we can use 38P(98.8Ah) or 39P(101.4Ah)

people mostly will use 3S38P so that’s 114 cells in total(3*38=114)

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is all clear to you now?

What If I drop the mAh rating from 2.6Ah to 2.2Ah(which is more common for type batteries), I now need 135 cells in total with 3S45P configuration to get the same total capacity of 11.1V 100Ah(actual capacity is 11.1V 99Ah).

PS: 11.1V/3.7V=3 100Ah/2.2Ah=45.5

The calculate is still on—

What if we use Lifepo4 cells(which are rated 3.2V 1.5Ah)? we would need 264 cells in total with 4S66P configuration to get the same total capacity of 11.1V 100Ah(actual capacity is 12.8V 99Ah).

PS: 11.1V/3.2V=3.5 people normally use 4S to boost voltage,

100Ah/1.5Ah=66.6

Let’s roll the ball on.

what will happen if Watt/Hour(Wh in short) are involved?

If you have, for example, 2Ah lithium ion battery cell then each of those stores 7.4Wh (3.7V*2Ah=7.4Wh) of energy and you need 136 of them (/7.4 ~ 136) for a 1kWh battery. 136 in parallel will give you a 1kWh battery with a nominal voltage of 3.7V.

If you want higher voltage, and you probably will, you have to put them in series as well. 7s is a typical minimum for a Home UPS battery. 136 cells can’t be evenly distributed over 7 packs in series, you then need 140 cells for a 7s20p setup.

All of above are just examples, there are plenty other possibilities. It would be very hard to put this into an automatic calculator which then provides meaningful results because almost all of this depends on variables the calculator doesn’t know or that have to be put in in the first place. It is easier to calculate this yourself.

Lithium batteries are a crucial component of modern technology, widely used in devices such as smartphones, power banks, electric tools, and new energy vehicles. However, there are significant differences among various types of lithium batteries in terms of materials, form factors, and performance. This article provides a detailed, professional overview of several common lithium batteries, their characteristics, advantages, disadvantages, and typical applications.

We often encounter different types of batteries, such as the battery, ternary lithium battery, lithium iron phosphate battery, lithium cobalt oxide battery, polymer lithium battery, blade battery, battery, and so on. With so many varieties of lithium batteries available, the question arises: What types of lithium batteries are used in the products we commonly see, and what are the differences between these types?

In fact, the terms related to lithium batteries can be categorized into three dimensions: form factor, cathode material, and electrolyte type. This helps clarify the distinctions. For example, a ternary lithium battery can be manufactured in a cylindrical shape like the or in a soft pack format. Similarly, smartphone batteries are typically polymer lithium-ion soft pack batteries with lithium cobalt oxide as the cathode material.

Dimensions for Categorizing Lithium Batteries:

• Form Factor: Includes cylindrical (e.g., ), prismatic, and soft pack batteries.
• Cathode Material: Different chemical compositions lead to variations in battery performance.
• Electrolyte Type: Can be liquid, solid, or polymer.

Detailed Overview of Major Lithium Battery Types:

1. Lithium Cobalt Oxide Battery (LiCoO2):

• Applications: Widely used in consumer electronics such as smartphones, tablets, and laptops.
• Advantages:
  • High Energy Density: Provides higher capacity for the same weight compared to other types, suitable for devices needing long battery life.
  • Stable Voltage Output: Ensures consistent performance.
• Disadvantages:
  • High Cost: Due to the expensive cobalt, these batteries are costlier.
  • Safety Issues: Potential for thermal runaway under overcharge, puncture, or high temperatures.
• Safety Measures: To mitigate risks, manufacturers use stricter quality controls, such as automated production lines and dust-free environments, as well as advanced safety protection circuits.

2. Ternary Lithium Battery (NCM/NMC):

• Applications: Mainly used in electric vehicles, portable electronics, and power tools.
• Advantages:
  • Balanced Performance: Offers a balance between energy density, safety, and lifespan.
  • Varied Options: By adjusting the proportions of nickel, cobalt, and manganese, performance parameters can be optimized.
• Disadvantages:
  • Complex Production: Requires advanced manufacturing processes, resulting in higher production costs.

Performance Table:

Characteristic 811 622 523 Energy Density High Medium Lower Safety Medium Higher High Lifespan Lower Medium High Cost High Medium Low

3. Lithium Iron Phosphate Battery (LiFePO4):

• Applications: Popular in new energy vehicles, outdoor power sources, and photovoltaic energy storage.
• Advantages:
  • High Safety: Excellent thermal stability and safe operation at low temperatures.
  • Long Lifespan: Can exceed charge cycles, suitable for long-term applications.
• Disadvantages:
  • Lower Energy Density: Larger and heavier, not ideal for weight-sensitive devices.
• Note: A significant drawback is poor low-temperature performance, which can severely reduce capacity in cold climates.

4. Lithium Manganese Oxide Battery (LiMn2O4):

• Applications: Commonly used in power tools, power banks, and some cost-effective electric vehicles.
• Advantages:
  • Low Cost: Lower material cost makes it suitable for large-scale production and use.
  • Good Safety: Performs well under high temperatures and overcharging conditions.
• Disadvantages:
  • Short Lifespan: Typically less than charge cycles.

Comprehensive Comparison of Lithium Battery Characteristics:

Type Applications Energy Density Safety Lifespan Cost Lithium Cobalt Oxide (LiCoO2) Smartphones, laptops, tablets High Low Medium High Ternary Lithium (NCM/NMC) Electric vehicles, electronics, tools Medium to High Medium to High High Variable Lithium Iron Phosphate (LiFePO4) Electric vehicles, energy storage Low to Medium High Very High Low Lithium Manganese Oxide (LiMn2O4) Power tools, power banks, budget EVs Low Higher Low Low

Considerations for Engineers and Industry Professionals:

When selecting a lithium battery, engineers should consider:

• Energy Density: Especially important for space and weight-constrained applications, such as portable devices and electric vehicles.
• Safety: Crucial in applications where personal safety is a concern, such as medical devices and aviation.
• Cost: Essential for cost-sensitive applications, including consumer electronics and large-scale energy storage systems.
• Environmental and Operating Conditions: The impact of extreme temperatures and mechanical stress on battery performance.

For more information on the lithium battery technology best suited for your application, please contact MOTOMA. Our expert team will provide tailored solutions to ensure you choose the highest performance battery products.

For more LiFePO4 Rechargeable Prismatic Batteryinformation, please contact us. We will provide professional answers.