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10 Technical Specifications to Include in Your Li-Po Battery RFQ

From my perspective on the factory floor at Hanery, the Request for Quotation (RFQ) is the single most important document in the entire sourcing process. It’s the blueprint for our partnership. A well-crafted RFQ, rich with technical detail, tells us immediately that we are dealing with a serious, professional partner. It allows our engineers to engage in a meaningful way, to design a solution that is not just adequate but optimal, and to provide a quote that is accurate and reliable.

Conversely, a vague RFQ is the start of a long, frustrating journey for everyone involved. We receive inquiries every day that say little more than “Quote for 10,000pcs 3.7V 1000mAh battery.” When we see this, we know what comes next: a long chain of emails trying to extract the critical details, a quote based on a dozen assumptions, and a high risk of the final product not meeting the client’s real-world needs. The buyer, in turn, receives ten different quotes from ten different suppliers, all based on different assumptions, making a true apples-to-apples comparison impossible.

This guide is designed to solve that problem. We are opening our engineering playbook to show you the ten most critical technical specifications that we, as a manufacturer, need to see in your RFQ. Providing this information will not only get you a faster, more accurate quote, but it will also fundamentally de-risk your project. It is the first and most important step in moving from a simple transactional purchase to a strategic manufacturing partnership that can deliver a truly world-class product.

1. How Should I Define the Battery's Voltage and Capacity?

This seems like the most basic specification, but the details matter immensely. Getting this right is the foundation of your battery’s performance.

Going Beyond a Single Number for Nominal Voltage

Nominal voltage (e.g., 3.7V for a single Li-Po cell) is just the average. The actual operating voltage of a battery changes as it discharges. A fully charged cell is around 4.2V, and a fully discharged one is around 3.0V. Your RFQ should specify the nominal voltage, but also the operating voltage range of your device. Why does this matter? If your device’s electronics have a brown-out protection that kicks in at 3.4V, you will be unable to use a significant portion of the battery’s energy. Sharing your device’s voltage window allows our engineers to ensure the battery and your product are a perfect electrical match.

Typical Li-Po Discharge Curve

Specifying "Minimum" vs. "Rated/Typical" Capacity

Capacity, measured in milliamp-hours (mAh), determines your product’s runtime. However, there’s a crucial distinction between “rated” or “typical” capacity and “minimum” capacity. Many datasheets will advertise the typical capacity, which is the average value. However, due to normal manufacturing variations, some cells will be slightly below this average. For an industrial or medical device where runtime is critical, you must specify the minimum acceptable capacity. This tells us the absolute floor for performance. We then select and grade our cells to guarantee that every single battery pack we ship will meet or exceed that minimum requirement, ensuring consistent performance for your end-users.

2. What Are the Absolute Maximum Physical Dimensions (and Tolerances)?

This is one of the most common and costly points of error. In modern compact electronics, space is at an absolute premium. A battery that is half a millimeter too thick can prevent your product’s enclosure from closing, leading to expensive rework of your mechanical design.

Defining a Hard "Not to Exceed" Envelope

Your RFQ must provide the absolute maximum dimensions for the battery in Length (L), Width (W), and Thickness (T), in millimeters. Think of this as the “bounding box” or the available cavity within your product. This is a “not to exceed” specification. Our engineers will then design a cell and pack assembly that fits comfortably within that envelope.

Accounting for the Full Pack Assembly, Not Just the Cell

A frequent mistake is to specify dimensions that only account for the bare Li-Po cell. The final battery pack is always larger. You must account for:

The thickness of the Battery Management System (BMS).
The thickness of the outer shrink wrap or hard case.
The space taken by wires and the connector.
Manufacturing tolerances.

A professional manufacturer will always add these elements into the final design. By providing us with the maximum available cavity size, you empower us to design the highest-capacity pack that will reliably fit, every time. It’s also helpful to provide a 3D CAD model of the available space if possible.

3. How Do I Specify the Maximum Continuous Discharge Current?

This is a measure of power. It defines how much current the battery can deliver steadily without overheating or degrading. Getting this wrong is a primary cause of poor performance and premature battery failure.

Using C-Rate vs. Amperes (A)

This can be specified in two ways:

In Amperes (A): e.g., “Maximum continuous discharge of 2A.” This is the clearest and most direct way.
In C-Rate: The “C” stands for capacity. A 1C rate for a 2000mAh battery is 2A (2000mA). A 0.5C rate is 1A. A 5C rate is 10A.

While C-rate is common, specifying the current in Amperes is less ambiguous.

Why This Spec Dictates the Cell and BMS Design

This single number has a massive impact on our design choices. A high continuous discharge requirement means we must select a “high-rate” Li-Po cell, which is engineered with different materials than a standard “high-energy” cell. It also means we must design the BMS with more robust MOSFETs and thicker nickel interconnects to handle the current without overheating. A pack designed for a 1A load will fail quickly and dangerously if used in a 5A application. Providing an accurate continuous discharge current is essential for both performance and safety.

4. How Should I Define the Peak or Pulse Discharge Current?

Many industrial devices, especially those with motors, pumps, or radio transmitters, do not draw a steady current. They have a low average draw but experience very high, short-duration current spikes. This is the peak, or pulse, current, and it is a critical specification that is often overlooked.

Specifying Both Magnitude and Duration

It’s not enough to say, “there’s a peak current.” You must specify both its magnitude (in Amps) and its duration (in milliseconds or seconds). For example: “The device has a peak current of 8A for 500 milliseconds during motor startup.”

Designing the BMS to Handle In-rush Currents

This specification is primarily for the BMS. The BMS’s over-current protection is designed to shut the battery down during a short circuit. If it’s not designed to tolerate your product’s normal in-rush current, it will see that peak as a fault and shut the power off. This will make your product appear to be dead or faulty. When we know the peak profile, we can select a BMS protection IC and MOSFETs that can safely handle that peak without tripping, while still providing robust protection against a genuine short circuit.

5. What Charge Profile Does My Product Require?

How the battery is charged has a huge impact on its safety and long-term cycle life. Your RFQ should specify the parameters of your charging system.

Defining Standard Charge Rate and Cut-off Parameters

The standard charge algorithm for Li-Po is CC-CV (Constant Current – Constant Voltage).¹ You should specify:

Maximum Charge Current: Typically, a standard charge is 0.5C (e.g., 1A for a 2000mAh battery).
Charge Cut-off Voltage: This is almost universally 4.2V for standard Li-Po cells.
Charge Termination Current: Charging should stop when the current tapers down to a certain level (e.g., 0.05C).

This information allows us to confirm that your charging design is appropriate for the cells we select.

Specifying "Fast Charge" Requirements (If Any)

If your product requires “fast charging,” this must be clearly stated. Fast charging (typically anything above 1C) puts significant stress on the battery. It requires the use of specially designed cells that can accept a high current without plating lithium, which can lead to internal short circuits. It also requires a more sophisticated BMS with very accurate voltage and temperature monitoring. Fast charging capability comes with trade-offs, often reducing the battery’s overall cycle life, so this is a key design decision we need to discuss with you.

6. In What Temperature Range Will the Product Operate?

A battery’s performance on a datasheet is always specified at a comfortable 25°C (77°F). An industrial product rarely lives in such a benign environment. Temperature is a critical factor that affects capacity, power output, and safety.

Defining the Full Discharge Temperature Range

You must specify the full range of ambient temperatures the device is expected to operate in.

Cold Temperatures: As temperature drops, a battery’s internal resistance increases. This reduces its available capacity and its ability to deliver high current. A battery might deliver only 70% of its rated capacity at 0°C. If your product needs to work in a refrigerated warehouse, we need to select special low-temperature cells.
Hot Temperatures: High temperatures (above 45°C) are the enemy of battery life, causing accelerated degradation.³ A battery operated continuously in a hot environment may only last half as long as one kept at room temperature.

Typical Li-Po Performance vs. Temperature

Defining the Charging Temperature Range

This is a critical safety specification. Charging a standard Li-Po battery below 0°C (32°F) is extremely dangerous. It can cause lithium plating, which can lead to an internal short circuit and fire. A properly designed industrial-grade BMS will have low-temperature protection that inhibits charging when it’s too cold. Your RFQ should specify the expected charging temperature range so we can ensure the BMS has the correct protective features.

7. What is the Target Cycle Life for the Application?

Cycle life determines how long the battery will last before it needs to be replaced. For an expensive industrial tool, the battery’s service life should align with the expected life of the product itself.

Defining "End of Life" (EOL)

Cycle life is defined as the number of full charge/discharge cycles until the battery’s capacity fades to a certain percentage of its initial capacity. The industry standard for EOL is typically 80%. Your RFQ should specify the target cycle life, for example: “The battery must deliver at least 500 cycles to 80% capacity.”

Understanding the Conditions That Affect Cycle Life

A 500-cycle life rating is not an unconditional guarantee. It is measured under specific laboratory conditions. The real-world cycle life will be affected by:

Charge/Discharge Rates: Higher rates reduce cycle life.
Temperature: Higher temperatures reduce cycle life.
Depth of Discharge (DoD): Consistently discharging to 0% is more stressful than cycling between 20% and 80%.

By specifying your target, you allow us to select a cell and recommend operating parameters that are designed to meet that longevity goal.

8. What BMS Features Are Required Beyond Basic Protection?

Every battery pack needs a BMS for basic safety. But for an industrial device, you often need more advanced “smart” battery features.

Basic Protections (The Non-Negotiables)

At a minimum, your RFQ should state that the BMS must include protections for:

Over-charge (cell level)
Over-discharge (cell level)
Over-current (charge and discharge)
Short circuit
Over/under-temperature

Advanced Features: Fuel Gauging and Communication

For a professional product, a simple LED indicator is not enough. You should specify if you need:

An Accurate Fuel Gauge (State of Charge – SoC): This requires a more advanced BMS with a “Coulomb counting” IC that measures the energy flowing in and out. This provides a much more accurate percentage display than simple voltage-based methods.
A Communication Protocol: Do you need the battery to report its status to your device’s main processor? If so, you must specify the protocol, such as I2C, SMBus, HDQ, or CAN bus. This allows your device to display detailed information like remaining capacity, time-to-empty, cycle count, and even fault codes, enabling a much richer user experience and predictive maintenance.

9. How Should I Specify the Wires and Connector?

This may seem like a minor detail, but getting it wrong can cause major production line headaches. An incorrect connector can halt your entire assembly process.

Providing an Exact Connector Part Number

Do not just say “a JST connector.” There are hundreds of different JST connector series. Your RFQ must include the exact manufacturer and part number for both the connector housing on the battery and the mating connector on your PCB. For example: “JST PHR-2 housing with JST SPH-002T-P0.5S terminals.” This eliminates all ambiguity.

Specifying Wire Gauge, Length, and Colors

You must also specify the requirements for the wires:

Length: How long do the wires need to be, in millimeters? Include a tolerance (e.g., 100mm +/- 3mm).
Gauge (AWG): The American Wire Gauge (AWG) determines the wire’s thickness and current-carrying capacity. This must be appropriate for your device’s current draw.
Colors: Specify the color for each wire (e.g., Red for +, Black for -, White for Thermistor, etc.).

Providing these precise details prevents incorrect assumptions and ensures the battery pack integrates perfectly with your product right out of the box.

10. What Safety and Shipping Certifications Are Required?

Certifications are a mandatory requirement for selling and shipping your product legally. They have a significant impact on the project’s cost and timeline, so they must be defined in the RFQ.

Defining the Target Markets and Required Certifications

You should list the countries or regions where you intend to sell the product, which then dictates the required certifications. The most common are:

UN38.3: Mandatory worldwide for shipping all lithium batteries.
UL (e.g., UL 2054, UL 1642): Primarily for the North American market. Often required by retailers.
CE: A mandatory self-declaration for selling in the European Union.
IEC 62133: The de facto international safety standard, recognized by many countries.

Clarifying Who is Responsible for the Certification Process

The RFQ should clarify the roles. Typically, we, as the manufacturer, are responsible for ensuring the battery component is designed to pass and for providing all necessary documentation. However, you, as the OEM, are the applicant for the final product certification. Stating these requirements upfront allows us to build the cost and time for testing into our quotation accurately.

Frequently Asked Questions

What if I don’t know some of these technical details, like the peak current?

That’s okay. A good manufacturing partner will help you figure them out. Provide us with as much information as you can about your product’s function (e.g., “it uses a 12V DC motor with a stall current of 5A”). Our engineers can then help you characterize your device’s power profile and determine the right specification.

What’s the difference between a PCM and a BMS?

A PCM (Protection Circuit Module) is a very simple board that provides only the most basic safety protections (over-charge/discharge/current). A BMS (Battery Management System) is more sophisticated. It almost always includes cell balancing (critical for cycle life) and can include advanced features like fuel gauging and communication. For most industrial applications, a BMS is required.

Does specifying a higher cycle life increase the battery cost?

Yes, typically it does. Cells that are engineered for a very long cycle life (e.g., 1000+ cycles) often use more stable, and therefore more expensive, chemistries and materials. However, this higher upfront cost is often justified by a lower Total Cost of Ownership (TCO).

How much does certification testing add to the cost?

The cost can range from a few thousand dollars for UN38.3 testing to tens of thousands of dollars for a full UL certification process. This is why it’s a critical item to include in the RFQ, as it’s a significant project cost.

What is a “thermistor” or “NTC”?

A thermistor (or NTC, Negative Temperature Coefficient resistor) is a small temperature sensor. We embed it inside the battery pack, and the BMS uses its reading to monitor the pack’s temperature and enable thermal protection. It is often connected to a third wire on the battery connector.

Why is it important to specify a “minimum” capacity?

Because all manufacturing processes have some variation. If you only specify a “typical” capacity of 2000mAh, you may receive some units that are 1950mAh, which may not meet your product’s runtime requirements. Specifying a “minimum” of, for example, 1980mAh, contractually obligates the manufacturer to ensure no unit falls below that line.

What does “cell balancing” do?

In a multi-cell pack, cell balancing is a BMS feature that ensures all cells are charged to the exact same voltage level. This prevents individual cells from being over-stressed and is the single most important feature for maximizing the pack’s long-term cycle life.

Can I just send you a competitor’s battery and ask you to copy it?

While we can analyze a competitor’s battery to understand its specifications (a process called reverse engineering), we will always create our own unique design that is optimized for your product. This ensures there are no IP infringement issues and allows us to build a better, more reliable solution.

Should I include my target price in the RFQ?

Yes, it is very helpful. Providing a realistic target price allows our engineers to engage in “design-to-cost.” We can make informed recommendations on different cell qualities or BMS features to help you meet your commercial goals without sacrificing critical performance or safety.

How should I format my RFQ document?

A simple, well-organized spreadsheet or a clear PDF document is perfect. List each of these ten specifications as a line item with your required value and any relevant notes. The clearer and more organized your RFQ, the better the responses you will receive.

Conclusion: A Detailed RFQ is a Strategic Tool

Crafting a detailed technical RFQ is not about creating more work. It is a strategic act that fundamentally de-risks your project and streamlines your entire sourcing process. It forces internal alignment within your own team, it ensures you receive accurate and truly comparable quotes from potential suppliers, and it establishes a clear, unambiguous technical baseline for your manufacturing agreement.

By providing these ten key specifications, you move the conversation with a potential supplier from a vague discussion about price to a detailed engineering collaboration focused on performance, reliability, and safety. It is the first, and most important, step in identifying and building a relationship with a true manufacturing partner who can help you deliver a successful, world-class product to the market.

If you are preparing an RFQ for your next project and need a partner who understands the importance of these technical details, we invite you to send it to our team. Let’s build something great together.

References

Cadex Electronics Inc. “Charging Lithium-Ion.” Battery University. Accessed via https://batteryuniversity.com/article/bu-409-charging-lithium-ion
M. S. Whittingham. “History, Evolution, and Future of Lithium-Ion Batteries.” Proceedings of the IEEE, 2014.
J. B. Goodenough, K. S. Park. “The Li-Ion Rechargeable Battery: A Perspective.” Journal of the American Chemical Society, 2013.
United Nations. “UN Manual of Tests and Criteria, Section 38.3.”
Underwriters Laboratories (UL). “UL 2054 – Standard for Household and Commercial Batteries.”
European Commission. “CE Marking.”
International Electrotechnical Commission. “IEC 62133-2:2017 – Safety requirements for portable sealed secondary cells.”
International Organization for Standardization. “ISO 9001:2015 – Quality management systems.”
American Wire Gauge (AWG) Chart and Current Limits. PowerStream Technology.
JST Connector Co. Official Website. (Reference for connector specifications).

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