Aug. 18, 2026
To specify a custom LiPo battery pack, I start with the device’s required voltage, capacity, peak current, operating environment, available space, charging method, and production target. I then convert these needs into a written battery specification covering cell configuration, protection electronics, connector, wires, enclosure, testing, packaging, and delivery requirements. This process helps OEM buyers compare suppliers on the same technical basis and reduces the risk of receiving a pack that fits electrically but not mechanically or operationally.
A custom lithium polymer battery is not defined by capacity alone. A reliable specification must connect the battery to the complete product system, including the load profile, charger, control board, safety requirements, and expected service conditions. In this guide, I explain the main decisions I use when preparing an OEM battery pack inquiry with TMK.
This guide is intended for product managers, electrical engineers, purchasing teams, and equipment manufacturers sourcing a custom LiPo battery for an OEM or private-label product. It is especially useful when an off-the-shelf battery cannot meet the required shape, discharge rate, connector, runtime, or installation method. It can also help buyers prepare a more complete request before contacting a battery manufacturer or exporter.
The recommendations apply to projects such as portable medical equipment, handheld terminals, robotics, smart instruments, security devices, consumer electronics, and other battery-powered systems. Final battery selection should always be reviewed against the product’s electrical design, applicable transport requirements, and intended market regulations.
A lithium polymer battery pack normally combines one or more pouch cells with wiring, connectors, insulation, and, where required, a protection circuit module or battery management system. The cell arrangement is commonly expressed as series and parallel configuration, such as 2S1P or 1S2P. Series cells increase nominal voltage, while parallel cells increase capacity and may improve current capability when the design and cell specifications support it.
Capacity is measured in ampere-hours, while energy is commonly estimated in watt-hours by multiplying nominal voltage by capacity. For example, a nominal 7.4 V pack rated at 2.0 Ah represents approximately 14.8 Wh before considering application losses. This figure is an estimate for energy comparison, not a guarantee of runtime, because actual usage depends on load, temperature, cutoff voltage, conversion efficiency, and battery aging.
Begin by identifying the device operating voltage and the acceptable voltage range for the electronics. I then check whether the system requires a single cell or a multi-cell pack, and whether the product design can accommodate a balancing circuit. Capacity should be based on the required operating time and load profile rather than selected only from the largest available value.
For example, a device drawing 1 A continuously may require more than a 2 Ah battery to operate for two hours, because the usable capacity is affected by cutoff voltage, temperature, discharge rate, and conversion losses. Buyers should provide both average current and peak current, together with the duration of each peak. This information allows the supplier to assess whether the selected cell can support the load without excessive voltage drop.
Discharge capability is often described using the C-rate. A 2 Ah cell specified at 10C may have a theoretical continuous discharge rating of 20 A, but the practical result still depends on the manufacturer’s conditions, temperature, wiring, connector, and protection circuit. I recommend requesting both continuous and peak discharge requirements instead of relying on a single C-rate value.
For high-rate applications, provide the peak current in amperes, peak duration in seconds, repetition frequency, and minimum acceptable voltage during the event. This is important for motor startup, wireless transmission, actuators, power tools, and robotics. A battery designed for high current may involve trade-offs in energy density, thermal behavior, cost, or service life.
Send the supplier a three-dimensional battery envelope rather than only a target length, width, and thickness. The envelope should identify restricted areas, cable exit locations, mounting points, compression limits, and the minimum bend radius for wires. Pouch cells can support flexible shapes, but they still require appropriate protection from puncture, sharp edges, compression, and uncontrolled movement.
I also recommend specifying the maximum finished pack dimensions, including tape, insulation, connector, and protection board. A nominal cell size may not represent the final assembled size. If the battery is installed in a sealed or compact product, include the available thermal path and any limits on surface temperature.
The protection design should be matched to the cell configuration and application. Depending on the project, the pack may need overcharge, over-discharge, overcurrent, short-circuit, temperature, and cell-balancing functions. The exact protection strategy should be confirmed with the battery supplier and the product engineer rather than added as a generic feature.
Provide charger output voltage and current, charging method, connector model, wire length, polarity, and mating requirements. A 1S LiPo pack and a 2S LiPo pack require different charging conditions, so the charger must be compatible with the selected configuration. I also ask buyers to define whether the pack needs a fuel-gauge interface, thermistor, communication line, switch, or custom terminal arrangement.
Application matching is the stage where electrical requirements are checked against real operating conditions. A handheld instrument may prioritize low thickness and moderate energy, while a robot may prioritize peak current, impact resistance, connector retention, and repeated cycling. A medical or monitoring device may place greater emphasis on traceability, controlled assembly, and predictable charging behavior.
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Environmental information is equally important. State the expected operating and storage temperature ranges, humidity exposure, vibration, shock, altitude, and whether the product is used indoors or outdoors. If the battery will be installed in an enclosure with limited ventilation, conservative thermal evaluation is appropriate because high load and elevated temperature can affect both performance and service life.
Record nominal voltage, operating voltage range, average current, peak current, peak duration, required runtime, and low-voltage cutoff. If the load changes by operating mode, provide a table showing the current and duration for each mode. This information is more useful than a simple statement such as “high-capacity battery required.”
List the maximum battery envelope, preferred cell shape, wire gauge, connector, cable direction, mounting method, and surface materials. Include drawings or photographs of the battery compartment when available. I recommend identifying non-negotiable dimensions separately from preferred dimensions so the supplier can suggest practical alternatives.
Specify the required protection functions, charging conditions, temperature sensing, appearance standards, labeling, packaging, and inspection points. Ask how the supplier verifies voltage, capacity, internal resistance, dimensions, connector polarity, and protection behavior. The exact test plan should be agreed before sampling, because test conditions can influence the reported results.
State prototype quantity, estimated annual demand, target launch date, sample approval process, acceptable substitutions, and destination market. Request separate information for sample pricing, production pricing, minimum order quantity, tooling, packaging, and shipping preparation. A clear commercial brief helps distinguish a technically suitable battery from one that is difficult to scale.
Most custom LiPo packs use pouch cells because their format can support compact product designs and various thickness requirements. Options may include single-cell or multi-cell configurations, standard or high-rate cells, different tab arrangements, protective films, foam pads, custom labels, and different wire or connector assemblies. The best option depends on the balance between capacity, current, size, thermal behavior, and cost.
Battery packs can also differ in their protection architecture. A basic protection circuit may be suitable for a simple application, while a more advanced system may be appropriate when the product requires monitoring, balancing, state-of-charge information, or communication. I advise buyers to define the required function first and avoid requesting unnecessary electronics that increase space and cost without improving the product.
Custom battery pricing is influenced by cell chemistry and grade, capacity, discharge performance, pack structure, protection electronics, connector, wire assembly, packaging, testing, and order volume. Small prototype orders often have a higher unit cost because setup, engineering review, and assembly preparation are distributed across fewer units. Production pricing should be evaluated only after the final design and test requirements are stable.
Minimum order quantity and lead time vary by design complexity, material availability, sample approval, and production scheduling. I recommend asking the supplier to separate engineering time, sample time, and mass-production time instead of accepting one general delivery estimate. Buyers should also confirm whether design changes after approval require a new sample or affect the production schedule.
When I evaluate a custom LiPo battery supplier, I look for clear technical communication and the ability to convert product requirements into a controlled specification. The supplier should explain assumptions, identify missing information, and distinguish confirmed data from preliminary estimates. This is often more valuable than a low initial quotation with unclear technical scope.
At TMK, I use the buyer’s electrical, mechanical, and commercial information to prepare a battery proposal for review. Depending on the project, our support can include pack configuration discussion, cell and protection selection, wire and connector coordination, sample preparation, and production communication. These options should be confirmed for each project because the available solution depends on the required design and order conditions.
One common mistake is specifying only voltage and capacity while omitting peak current, dimensions, charger information, and connector details. Another is using a nominal capacity figure as a guaranteed runtime without defining the discharge conditions or cutoff voltage. Buyers may also overlook the finished thickness of protection boards, wires, insulation, and labels.
A further risk is approving a sample without testing it inside the final device. Bench testing may confirm basic voltage and capacity, but it may not reveal enclosure pressure, connector interference, thermal limitations, or voltage drop during peak loads. I recommend validating the battery in the actual product and recording the acceptance criteria before production approval.
A successful custom LiPo battery specification connects the battery’s electrical performance with the product’s mechanical space, charger, operating environment, protection needs, and purchasing plan. The most important information to prepare is nominal voltage, capacity, average and peak current, runtime, maximum dimensions, connector details, charging conditions, temperature range, and expected quantity. A complete request gives the supplier a practical basis for proposing a safe and manufacturable OEM pack.
If you are preparing a custom LiPo battery project, send TMK your target voltage, capacity, dimensions, current profile, connector, charger details, application, sample quantity, and expected production volume. I can then help organize the requirements into a clearer OEM battery pack specification and identify the technical points that need confirmation before sampling.
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