1. 4-Dimension Specification Framework for OEM Custom Battery Pack

The 4-dimension specification framework for the OEM custom battery pack covers the voltage matching, the protection circuit (PCM/BMS), the connector type, and the chemistry selection (Ni-MH vs Ni-Cd vs Li-Ion). The 4-dimension framework is the standard procurement specification for portable device manufacturers who need to source the custom battery pack configuration for the medical device, the consumer electronics, the power tool, the e-bike, and the industrial sensor application. The ZS Cells engineering team provides the 4-dimension specification framework with the per-application verification spec.

The voltage matching is the first specification dimension the procurement team should evaluate. The standard voltage range for the OEM custom Ni-MH/Ni-Cd battery pack falls between 1.2V (single cell) and 12V (10-cell pack). The voltage configuration determines the portable device operating voltage and the runtime per charge. The procurement team should request the per-pack voltage specification from the supplier with the documented voltage tolerance per the cell specification.

The 6-step OEM custom battery pack design process is the second verification spec the procurement team should request. The standard design process includes (1) the requirement clarification (voltage + capacity + current + connector + PCM), (2) the cell selection (Ni-MH vs Ni-Cd vs Li-Ion by the application), (3) the cell matching (cell-to-cell voltage and capacity tolerance), (4) the pack assembly (series + parallel configuration), (5) the PCM/BMS integration (protection circuit installation), and (6) the per-pack test (voltage tolerance + capacity test + cycle test + PCM/BMS function test). The ZS Cells engineering team provides the 6-step design process documentation with the per-pack specification sheet.

The custom battery pack procurement workflow is the third verification spec the procurement team should evaluate. The standard procurement workflow includes (1) the RFQ (request for quotation) submission with the specification sheet, (2) the engineering review and the design feedback from the supplier, (3) the sample manufacturing and the sample test report submission, (4) the production tooling and the production schedule confirmation, (5) the mass production with the per-batch quality control documentation, and (6) the logistics and the after-sales support with the warranty documentation.

2. Voltage Matching by Cell Series Configuration

The voltage matching by cell series configuration determines the portable device operating voltage. The standard series configurations include 1 cell (1.2V), 2 cells (2.4V), 3 cells (3.6V), 4 cells (4.8V), 5 cells (6.0V), 6 cells (7.2V), 7 cells (8.4V), 8 cells (9.6V), 9 cells (10.8V), and 10 cells (12.0V). Each series cell adds 1.2V to the pack voltage within the ±2% voltage tolerance per cell.

The voltage tolerance specification is the second verification spec the procurement team should request. The standard voltage tolerance per cell is ±2% at the fully charged condition. The pack voltage tolerance typically falls within ±3% to ±5% depending on the number of cells and the cell-to-cell variation. The procurement team should request the per-pack voltage test report from the supplier with the documented test methodology and the per-cell voltage measurement.

3. Protection Circuit (PCM/BMS) Design for the Custom Battery Pack

The protection circuit (PCM/BMS) design is the third specification dimension the procurement team should evaluate. The standard PCM for the Ni-MH/Ni-Cd custom battery pack includes the overcharge protection (1.45V per cell threshold), the overdischarge protection (0.9V per cell threshold), the short circuit protection (with the auto-recovery), and the overcurrent protection (with the per-pack current threshold). The PCM should support the 1.45V to 1.55V overcharge threshold range for the Ni-MH cell chemistry.

The BMS (Battery Management System) is the alternative protection design for the larger battery pack with the higher complexity requirement. The BMS typically supports the cell balancing (active or passive), the temperature monitoring, the state of charge (SOC) calculation, and the state of health (SOH) reporting. The procurement team should request the BMS specification with the documented cell balancing method, the temperature sensor count, and the SOC calculation algorithm.

The PCM vs BMS selection is the fourth verification spec the procurement team should evaluate. The PCM is typically selected for the small to medium battery pack (1 to 6 cells in series with the capacity below 5000 mAh). The BMS is typically selected for the larger battery pack (7 or more cells in series with the capacity above 5000 mAh). The ZS Cells engineering team provides both the PCM and the BMS designs with the per-pack specification sheet.

4. Connector Type Selection for the Custom Battery Pack

The connector type selection is the fourth specification dimension the procurement team should evaluate. The standard connector types include the JST PH 2-pin connector (for the low-current portable device), the JST XH 2-pin connector (for the medium-current portable device), the Molex Mini-Fit 2-pin connector (for the power tool), the XT60 connector (for the high-current RC and e-bike), and the DC barrel jack (for the low-voltage consumer electronics).. For reference on the ZS Cells company background and the manufacturing capability, see the ZS Cells company profile page.

The connector rating specification is the fifth verification spec the procurement team should evaluate. The standard JST PH connector supports the 1 to 2 A continuous current rating with the 5 A peak current. The standard JST XH connector supports the 2 to 3 A continuous current rating with the 7 A peak current. The Molex Mini-Fit connector supports the 5 to 9 A continuous current rating with the 12 A peak current. The procurement team should request the per-connector specification from the supplier with the documented cycle life (typically 30 to 100 mating cycles).

5. Ni-MH vs Ni-Cd Chemistry Selection

The Ni-MH vs Ni-Cd chemistry selection is the fifth specification dimension the procurement team should evaluate. The Ni-MH chemistry provides the higher capacity per cell (AA Ni-MH provides 1300 to 2700 mAh vs AA Ni-Cd provides 600 to 1000 mAh) with the -10 to 45 degrees Celsius operating temperature range. The Ni-Cd chemistry provides the higher discharge current capability with the -20 to 60 degrees Celsius operating temperature range. The procurement team should request the per-chemistry specification from the supplier with the documented cell data sheet.

The Ni-MH chemistry is the preferred selection for the consumer electronics and the portable device application. The Ni-MH chemistry supports the higher energy density per cell and the longer runtime per charge. The Ni-Cd chemistry is the preferred selection for the power tool, the emergency lighting, and the industrial sensor application. The Ni-Cd chemistry supports the higher discharge current capability and the wider operating temperature range. The ZS Cells Ni-Cd battery category product portfolio covers the AA / AAA / C / D / SC Ni-Cd cells and the OEM custom battery pack integration.

The Li-Ion chemistry is the alternative selection for the higher energy density requirement. The standard Li-Ion cell (18650 / 21700) provides the 2000 to 5000 mAh capacity with the 3.6V to 3.7V nominal voltage per cell. The Li-Ion pack supports the higher energy density per weight (typically 150 to 250 Wh/kg) vs Ni-MH (typically 60 to 100 Wh/kg). The Li-Ion pack requires the BMS with the cell balancing and the per-cell voltage monitoring. The procurement team should specify the chemistry per the portable device energy density requirement and the safety certification requirement.

The LiFePO4 chemistry is the alternative selection for the higher safety and the longer cycle life requirement. The LiFePO4 cell provides the 3.2V nominal voltage per cell with the 2000 to 3500 cycle life. The LiFePO4 chemistry supports the wider operating temperature range (-20 to 60 degrees Celsius) and the higher safety vs the standard Li-Ion chemistry. The procurement team should specify the LiFePO4 chemistry for the medical device, the e-bike, and the energy storage application.

6. Cell Configuration Specification and Custom Pack Design

The cell configuration specification determines the series and parallel combination of the Ni-MH/Ni-Cd cells in the custom battery pack. The series connection increases the voltage per the cell count. The parallel connection increases the capacity per the parallel group. A typical 4.8V 2000 mAh pack uses 4 AA Ni-MH cells in series (4S configuration). A typical 6.0V 4000 mAh pack uses 5 AA Ni-MH cells in series with the 2-parallel (5S2P) configuration for the doubled capacity.

The cell-to-cell matching is the sixth verification spec the procurement team should request. The standard cell-to-cell voltage tolerance is ±0.02V per cell at the fully charged condition. The cell-to-cell capacity tolerance is ±5% per cell at the C/5 discharge rate. The procurement team should request the cell matching documentation from the supplier with the documented cell selection method and the per-cell voltage and capacity measurement.

7. Capacity and Cycle Life Specification

The capacity specification determines the runtime per charge for the portable device. The standard capacity range of the OEM custom Ni-MH battery pack falls between 600 mAh (single AAA Ni-MH cell) and 20000 mAh (10S2P configuration with the 18650 Li-Ion cell). The AA Ni-MH cell provides the 1300 to 2700 mAh range. The AA Ni-Cd cell provides the 600 to 1000 mAh range. The procurement team should specify the capacity per the portable device runtime requirement.

The cycle life specification is the seventh verification spec the procurement team should evaluate. The consumer-grade Ni-MH pack typically supports the 500 cycle life. The industrial-grade Ni-MH pack typically supports the 1000 to 1500 cycle life. The Ni-Cd pack typically supports the 800 to 2000 cycle life with the higher cycle capability per the chemistry advantage. The procurement team should request the per-cycle test data from the supplier with the documented test methodology and the cycle termination criteria (typically the 60% to 80% of the initial capacity).

The energy density comparison is the eighth verification spec the procurement team should evaluate. The standard Ni-MH pack provides the 60 to 100 Wh/kg energy density. The standard Ni-Cd pack provides the 40 to 60 Wh/kg energy density. The standard Li-Ion pack provides the 150 to 250 Wh/kg energy density. The standard LiFePO4 pack provides the 90 to 160 Wh/kg energy density. The procurement team should specify the energy density per the portable device weight requirement and the runtime per charge requirement.

8. Operating Temperature and Storage Specification

The operating temperature specification determines the portable device deployment condition. The Ni-MH pack typically supports the -10 to 45 degrees Celsius operating temperature range for the discharge cycle. The Ni-MH pack typically supports the 0 to 45 degrees Celsius operating temperature range for the charge cycle. The Ni-Cd pack typically supports the -20 to 60 degrees Celsius operating temperature range for both the charge and the discharge cycle. The procurement team should specify the operating temperature per the portable device deployment condition.

The storage specification is the eighth verification spec the procurement team should request. The standard Ni-MH/Ni-Cd pack storage temperature falls between -20 and 35 degrees Celsius. The standard storage humidity is below 65% relative humidity. The standard self-discharge rate falls between 15% and 25% per month for the Ni-MH cell at the room temperature. The standard self-discharge rate falls between 10% and 20% per month for the Ni-Cd cell at the room temperature. The procurement team should request the storage specification documentation from the supplier.

9. 5-Step BOFU OEM Custom Battery Pack Procurement Checklist

For portable device manufacturers ready to specify the OEM custom battery pack with the 4-dimension specification framework, the following 5-step checklist consolidates the verification specs from the previous sections into a single procurement specification document.

1. Define the voltage matching by the cell series configuration (1 cell to 10 cells) with the per-pack voltage tolerance.
2. Specify the protection circuit (PCM for small packs / BMS for large packs) with the threshold specification.
3. Select the connector type (JST PH / JST XH / Molex Mini-Fit / XT60 / DC barrel jack) with the rated current requirement.
4. Choose the chemistry (Ni-MH for portable device / Ni-Cd for power tool and industrial sensor) with the operating temperature range.
5. Document the capacity, the cycle life, the operating temperature, and the storage specification with the per-pack test documentation.

For portable device manufacturers and the procurement teams sourcing the OEM custom battery pack, the following industry resources provide cross-reference data on the battery specification standards and the portable device compliance framework. The International Electrotechnical Commission (IEC) publishes the IEC 61951 and IEC 62133 standards for the Ni-MH and Ni-Cd battery safety and performance. The International Organization for Standardization (ISO) publishes the ISO 9001 quality management standard and the ISO 14001 environmental management standard. The UL (Underwriters Laboratories) publishes the UL 1642 lithium battery safety standard and the UL 2054 household battery standard. The Institute of Electrical and Electronics Engineers (IEEE) publishes the IEEE 1625 and IEEE 1725 standards for the rechargeable battery in mobile computing. The Battery University provides the technical reference material for the battery chemistry and the custom battery pack design.

For portable device manufacturers ready to specify the OEM custom battery pack with the 4-dimension specification framework, the ZS Cells engineering team can provide the cell matching documentation, the PCM/BMS design documentation, the connector prototype, and the per-pack test report. The ZS Cells engineering team has supported portable device manufacturers with documented deployments across the medical device, the consumer electronics, the power tool, the e-bike, and the industrial sensor markets. Review the ZS Cells Ni-Cd battery category for the cell selection and the OEM custom pack integration options, or visit the ZS Cells home page for the full product portfolio.

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