18650 Battery Pack Calculator and Planner
Select a cell from the cell database
Use this autocomplete search functionality to find your specific cell in order to pre-populate the values that we have for that cell.
Single cell information
Enter information on a single cell into the input fields to receive results for a single cell. Results will automatically generate every time a value changes and there is enough information to calcualte results.
The C-rate will be used down below at pack level calculations, so make sure you fill this section out.
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Pack level information
Enter information related to your up-and-coming pack to get all kinds of information on the pack.
The C-rate, voltage, and capacities from the single-cell step will be used to calculate information in this step. Make sure that you fill out the fields above to get accurate results in this section.
If this is your first time planning out a battery pack, check out our guide on how to build an 18650 battery pack .
Virtual battery life calculator
This section allows you to get an idea of approximately how long the battery life of the pack you are building will be. For now this calculates battery life at a fixed load amount, if you have ideas on how we can improve this calculator's functionality fill out a contact form and let us know!
For example If you plan on running something that consumes 1000W and your battery pack is 1kwh you can now estimate the life of the battery at a given load in watts.
Pack weight and cell cost
This section estimates the cost and weight of the pack based on cell count, single cell weight, and cost per cell.
The series and parallel information from the above step are used to calculate this information, so make sure you fill out the above step first.
Keep in mind that you'll also need to add a BMS to your pack, so that will add to the overall cost and weight. Check out this post we wrote to learn about choosing a BMS for your lithium ion battery pack.
How to Use Our Battery Pack Calculator and Planner
Before using our battery pack planner it is important to carefully consider your specific needs and then select the cells and configuration of those cells to make sure they meet your needs. While you can use our battery calculator which is designed to help with this process, here are general steps to use a battery pack planner:
- Define Your Requirements: Determine the following requirements for your battery application, safe available, voltage (V), amperage (A), and capacity (Ah or Wh).
- Select Cells: Choose the appropriate cells based on your requirements. Pay attention to cell chemistry, size, weight, and available space for the cells. It rarely works out that any one cell is the perfect fit, I always pick a cell that can provide at least 110% of current demand.
- Battery Configuration: Decide whether you need to connect the cells in series, parallel, or both to achieve the desired voltage and capacity. Series connections increase voltage, while parallel connections increase capacity.
- Voltage Compatibility Ensure that the voltage of your battery pack is compatible with the voltage requirements of your devices or system. Make sure you check compatibility at the highest charge and lowest discharge voltages. Be mindful of voltage drop over time, especially as the battery discharges.
- Battery Management System (BMS): Incorporate a Battery Management System (BMS), yeah I get it you don't want to spend the money or don't think you need one but it is insurance and it can help increase the lifespan of the pack. Make sure you choose the right BMS for your specific needs. A BMS helps monitor and protect the cells and the pack as a whole, ensuring it all operates safely.
- Charging and Discharging: Choose an appropriate charger that matches your battery pack's voltage and doesnt charge your battery too fast. Make sure to factor in the appropriate battery connectors and wire size to make sure both can handle the current. Make sure they are compatible with the BMS if you have one.
- Safety Measures: Account for safety measures such as overcharge and over-discharge protection, thermal management, and short-circuit protection in your battery pack design. Your BMS should handle all of these things but being aware of them is important.
- Physical Layout: Plan the physical layout of the battery pack, considering factors like size, weight distribution, and how it will be mounted or integrated into your application.
- Testing and Validation: Before using your battery pack, thoroughly test it to ensure it meets your requirements and safety standards. Monitor its performance and make any necessary adjustments.
Once you have gone through everything above you should use our battery pack planner tool, it will help give more accurate recommendations for battery cell selection and pack configuration. This tool will simplify the planning process and help ensure you meet your power supply needs. We have other tools available like our BMS picker tool and our battery pack designer which is in development.
Battery Calculator and Planner Definitions
- Nominal Voltage: Often referred to as "rated voltage" or "design voltage," is a specific voltage that represents the standard or expected voltage level of a battery cell. This can be found by checking the manufacturers' datasheet.
- Minimum and Maximum Voltage: These are the lowest and highest levels at which a cell can safely provide power. Staying within these limits is crucial for proper equipment operation and safety. This voltage range can be found by looking up the manufacturers' datasheet.
- Rated Capacity in Ah (Ampere-hours): This is the amount of electrical charge a cell or battery pack can provide or store. It indicates how long a battery can deliver a specific current before needing recharging. If your datasheet only shows mAh the math is simple mAh/1000= Ah. If you do not know the Ah value the formula to calculate is Ah=Wh/V
- C-rate: This is a measure of how fast a battery or cell can be charged or discharged in relation to its capacity. It's expressed as a ratio of current (in amperes, A) to the battery or cell capacity (in Ampere-hours, Ah). For example, a 2C discharge rate means the battery is being discharged at twice its capacity, while a 0.5C charge rate means it's being charged at half its capacity. So a 2000mAh cell that can be discharged at 2C can supply (2000mAh x 2C = 4amps) 4amps of current.
- Cells in Series: This is when you connect cells in a chain-like configuration, where the positive terminal of one cell is connected to the negative terminal of the next cell. Each chain of this configuration adds 1 series group. This results in an additive increase in voltage while the overall capacity remains the same. This arrangement is commonly used to create battery packs with higher voltage outputs, as it allows you to harness the cumulative voltage of the individual cells.
- Cells in Parallel: This is when you connect cells in groups where all the positive terminals are connected, and all the negative terminals are connected. Each cell in this group counts as adding 1 in parallel. This setup maintains the same voltage but increases the overall capacity and current rating of the battery pack. This makes it useful for applications where you want to extend the runtime without changing the voltage level or need to supply more current than a single cell can handle.