Views: 0 Author: ZERNE Battery Technical Content Team Publish Time: 2026-08-17 Origin: Site
A custom lithium battery project rarely fails because the buyer does not know the required capacity. More often, problems begin when the initial specification is incomplete.
An OEM team may provide a target voltage and capacity but leave out the battery compartment, peak current, connector position, charging method, operating temperature, or protection requirements. The supplier may then prepare a quotation based on assumptions. Those assumptions can create problems during sampling, device integration, or mass production.
A practical custom battery design process should therefore begin with a complete project brief. The goal is not to make the buyer decide every technical detail alone. The goal is to provide enough reliable information for the manufacturer to assess feasibility, recommend a suitable battery architecture, and identify the requirements that still need confirmation.
This checklist covers the main information needed before requesting a quotation or custom battery sample.
OEM buyers should normally prepare the following information:
Requirement | Information to Provide |
|---|---|
Application | Device type, operating conditions, and intended use |
Voltage | Nominal voltage, operating voltage, and charging voltage |
Capacity | Required capacity, energy, and target runtime |
Current | Normal, continuous, peak, and startup current |
Dimensions | Maximum length, width, thickness, and weight |
Interface | Connector, cable length, wire exit position, and communication needs |
Protection | PCM, BMS, NTC, temperature protection, and balancing requirements |
Environment | Operating temperature, storage conditions, vibration, and humidity |
Production | Prototype quantity, expected production volume, and target schedule |
Compliance | Required test reports, transport documents, and market requirements |
The more complete the project information, the easier it is to evaluate a custom lithium ion battery before design, quotation, sampling, and production.
The battery should be designed around the device rather than selected as an isolated component.
Start by describing:
What the device does;
How often it operates;
Whether it works continuously or intermittently;
Whether it has standby and active modes;
Whether it is portable, fixed, wearable, or industrial;
Whether the battery is replaceable or permanently installed;
Whether the device communicates wirelessly;
Whether the battery is exposed to vibration, impact, moisture, or temperature changes.
For example, a GPS tracker may spend most of its time in standby but require short periods of higher current for positioning and data transmission. A medical device may require stable output and carefully controlled protection. A wearable product may place greater importance on thickness, weight, flexibility, and comfort.
The application information helps the manufacturer evaluate the relationship between capacity, current demand, size, protection, and expected runtime.
Voltage is one of the first specifications that must be confirmed.
The specification should distinguish between:
Nominal voltage;
Normal operating voltage;
Full-charge voltage;
Cutoff voltage;
Device input-voltage range;
Charger output requirements.
A device may be designed around a single-cell battery or a multi-cell battery pack. The required voltage may influence the cell configuration, protection circuit, charging system, connector, and battery management strategy.
Do not provide only a phrase such as “12 V battery” without explaining how the device and charger use that voltage. The manufacturer also needs to know whether the device accepts voltage variation during discharge and whether a regulated output is required.
A voltage mismatch may result in:
Charging incompatibility;
Device shutdown;
Reduced usable capacity;
Excessive current demand;
Protection activation;
Additional power-conversion requirements.
Voltage should therefore be reviewed together with the device’s power-input and charging design.
Capacity is usually expressed in milliampere-hours, or mAh. Larger capacity can support longer runtime, but it may also increase battery size, weight, cost, and charging time.
Provide the following information where possible:
Required capacity in mAh or Ah;
Target runtime;
Average operating current;
Standby current;
Peak-current duration;
Duty cycle;
Expected battery reserve;
Charging frequency;
Acceptable battery weight.
For higher-power applications, it can also be useful to discuss energy in watt-hours:
Energy (Wh)=Nominal Voltage (V)×Capacity (Ah)
A battery’s usable runtime depends not only on its nominal capacity but also on device load, operating temperature, discharge rate, cutoff settings, charging conditions, and system efficiency.
A useful OEM specification should not simply state:
Required battery: 3.7 V, 2,000 mAh.
It should explain:
The device requires a rechargeable battery with a nominal voltage compatible with the system, a target capacity of approximately 2,000 mAh, a defined operating current, a peak-current requirement, and a minimum expected runtime under specified operating conditions.
The final capacity should be confirmed through sample testing rather than selected only from a catalog value.
Current demand affects cell selection, voltage drop, internal resistance, protection settings, and thermal behavior.
The design brief should separate:
Normal operating current;
Continuous maximum current;
Peak current;
Startup or inrush current;
Peak-current duration;
Frequency of peak events;
Charging current.
A device that consumes a low average current may still require a battery capable of delivering a much higher short-term current. If this is not identified during the design stage, the battery may experience excessive voltage sag or trigger over-current protection.
Peak current should be described with a time period. For example:
2 A for normal operation;
5 A peak for 3 seconds;
Peak event repeated once every 10 minutes.
This information is more useful than a general statement such as “high-current battery.”
Mechanical fit is a core part of custom battery design.
Provide a drawing, 3D model, or accurate measurements of the battery compartment, including:
Maximum length;
Maximum width;
Maximum thickness;
Available height;
Installation direction;
Mounting points;
Retention method;
Clearance around the battery;
Space for the protection board;
Space for the connector and wires;
Cable routing;
Access for replacement or inspection.
Do not measure only the empty compartment. The design should also consider:
Insulation;
Protective materials;
Connector height;
Cable bending radius;
Manufacturing tolerance;
Assembly clearance;
Heat dissipation;
Mechanical compression;
Possible dimensional variation during production.
For compact products, a difference in connector position or cable outlet direction can prevent the battery from fitting even when the cell dimensions appear correct.
ZERNE’s custom lithium battery solutions can be evaluated according to required dimensions, capacity, protection system, connector, and application conditions. The final design still needs to be confirmed against the actual device enclosure.
A custom lithium battery may use a standard rectangular format, a thin format, a curved design, or another shape suited to the equipment.
The specification should identify whether the battery needs:
A standard rectangular shape;
A thin and flat structure;
A curved or shaped form;
A multi-cell battery pack;
A removable case;
A rigid enclosure;
A custom mounting structure;
A particular cell orientation.
The choice should be based on the device structure and production requirements. A fully customized shape may improve space utilization, but it can also affect tooling, assembly, inspection, packaging, and production consistency.
For a regular rectangular compartment, a standard structure may be more practical. For irregular or highly compact devices, a shaped or thin battery may provide better integration.
Before committing to a fully customized structure, OEM teams can also compare the trade-offs between a custom lithium battery and an off-the-shelf battery pack.
The design should also define whether the battery pack requires:
Series connection;
Parallel connection;
Series-parallel configuration;
Cell matching;
A separate protection board;
A communication-enabled BMS.
The connector is part of the battery interface and should be confirmed before sampling.
Provide:
Connector brand or series, if required;
Number of pins;
Connector orientation;
Connector location;
Cable length;
Wire gauge;
Wire exit direction;
Polarity;
Balance lead requirements;
Charging lead and discharge lead arrangement.
A battery may have the correct voltage and capacity but still fail device integration because the connector is not compatible with the mainboard or because the cable exits from the wrong side.
The connector should be reviewed together with:
Available space;
Insertion direction;
Locking method;
Vibration conditions;
Assembly sequence;
Service requirements;
Required current.
For more detailed connector considerations, refer to LiPo battery connectors and custom wiring options.
The protection system should be selected according to the battery architecture and device requirements.
The design brief should clarify whether the project needs:
Overcharge protection;
Over-discharge protection;
Over-current protection;
Short-circuit protection;
Temperature monitoring;
Cell balancing;
State-of-charge information;
Communication functions;
Charging and discharging control;
A smart battery interface.
A single-cell battery may use a protection circuit with relatively simple functions. A multi-cell battery pack may require a more advanced BMS for cell monitoring, balancing, fault recording, communication, or system integration.
The buyer should also explain the role of the protection system:
Is the charger controlled by the battery?
Does the device need battery status information?
Is an NTC required?
Does the device communicate through SMBus, CAN, or another protocol?
Does the BMS need to be located inside or outside the battery enclosure?
For a general explanation of protection-system selection, link to PCM vs. BMS for LiPo batteries.
Battery performance and design requirements can change significantly with the operating environment.
The specification should include:
Operating temperature range;
Storage temperature;
Charging temperature;
Humidity;
Vibration;
Shock;
Dust or water exposure;
Altitude;
Indoor or outdoor use;
Expected service life;
Storage duration before installation.
Temperature is especially important because charging and discharging conditions may not be the same. A battery used outdoors, inside an industrial device, or near a heat-generating component may need additional thermal evaluation.
The design should also identify whether the battery compartment is:
Fully enclosed;
Ventilated;
Near a heat source;
Exposed to direct sunlight;
Subject to repeated mechanical movement.
These details should be considered before selecting the cell, protection system, enclosure, and testing plan.
A custom battery should be compatible with the intended charging system.
Provide:
Charger type;
Charger output voltage;
Maximum charging current;
Charging method;
Balance-charging requirements;
Charging connector;
Charging temperature limits;
Expected charging time;
Whether charging occurs inside the device.
The battery manufacturer should understand how the charger, battery, protection system, and device work together. A battery specification that excludes the charger may be incomplete.
The charger should not be selected only according to nominal battery capacity. It should also match the battery configuration, protection settings, charging voltage, current limits, and application conditions.
Before mass production, the battery design should be validated against the device.
The initial project brief should identify the expected validation scope, such as:
Capacity testing;
Charge and discharge testing;
Runtime verification;
Peak-current testing;
Internal-resistance measurement;
Temperature monitoring;
Connector and cable inspection;
Mechanical fit;
Vibration or impact testing;
Repeated charging and discharging;
Device-level integration testing.
The test conditions should be defined as clearly as possible. Capacity results can vary depending on current, temperature, cutoff voltage, charging method, and test equipment.
The sample should represent the intended production design. If the cell, protection board, connector, wire, or enclosure changes after testing, the project may require additional review or revalidation.
For a stage-by-stage view of requirement review, prototype development, validation, pilot production, and mass production, see From Prototype to Mass Production: Custom Battery Development Stages.
This article focuses on information needed before design and quotation. Detailed sample acceptance criteria should be handled in a separate battery sample validation guide.
Compliance requirements depend on the battery construction, destination market, product category, transportation method, and customer requirements.
Before quotation, identify whether the project may require:
UN 38.3 test documentation;
SDS or MSDS;
Product specifications;
Battery labels;
Transport documents;
RoHS or other material declarations;
Market-specific requirements;
Customer-specific inspection records.
The buyer should also clarify:
Destination countries;
Shipping method;
Product classification;
Whether the battery is shipped installed in equipment;
Whether the customer needs a test report or declaration;
Whether documents must cover a specific battery model or production design.
Certification and transport documentation should be reviewed against the final battery construction. A document for an earlier prototype may not automatically represent a later production design.
Before requesting a quote, confirm the following items.
Device name and application;
Operating modes;
Runtime target;
Operating environment;
Expected production stage.
Nominal voltage;
Full-charge voltage;
Capacity;
Normal current;
Peak current;
Charging current;
Cutoff requirements.
Maximum length;
Maximum width;
Maximum thickness;
Weight limit;
Connector space;
Mounting method;
Cable route;
Enclosure clearance.
PCM or BMS;
NTC;
Cell balancing;
Communication;
Connector;
Wire length;
Wire exit position.
Prototype quantity;
Estimated production volume;
Sample testing requirements;
Target market;
Documentation needs;
Packaging and shipping requirements.
If the project is moving toward quotation, the main cost drivers should also be reviewed. A separate guide on custom lithium battery pack cost and OEM pricing factors can help procurement teams prepare for that discussion.
The first step is to define the device application and its electrical, mechanical, environmental, and production requirements. A battery should be designed around the equipment rather than selected only by voltage or capacity.
Send the battery voltage, capacity, current demand, dimensions, connector details, application, operating environment, expected quantity, and any PCM/BMS, testing, or compliance requirements.
Custom battery dimensions can be developed according to the device structure and available installation space. The final size must include insulation, protection components, connectors, cables, tolerances, and assembly clearance.
You should explain the device and protection requirements, but you may not need to select the exact BMS model yourself. The manufacturer can recommend a suitable PCM or BMS after reviewing the battery configuration, current, charging method, communication needs, and operating conditions.
The connector affects electrical compatibility, assembly, cable routing, available space, and serviceability. Connector type, polarity, position, cable length, and wire exit direction should be confirmed before sampling.
The sample may need capacity, charge and discharge, runtime, current, temperature, mechanical-fit, connector, and device-integration testing. The final validation plan should match the application and agreed specification.
A complete specification is the foundation of a successful custom lithium battery project.
Before requesting a quotation or sample, OEM buyers should define the application, voltage, capacity, current demand, dimensions, battery structure, connector, protection system, charging method, operating environment, testing requirements, production expectations, and compliance documents.
The purpose of a custom battery design checklist is not to force the buyer to make every technical decision alone. It is to give the battery manufacturer enough reliable information to assess feasibility, identify risks, recommend a suitable design, and prepare a more accurate quotation.
