Custom 18650 battery packs

18650 lithium battery pack customization process, 18650 lithium battery pack customization requirements. In the process of battery production and assembly, the 18650 lithium battery pack has very strict requirements on each step of the process. The lithium battery customization process usually takes less than 15 working days. As an emerging industry, lithium batteries have developed rapidly in the past two years, and more and more companies have applied lithium battery packs to their own products. Lithium battery pack customization came into being in this big environment.

How we build the best custom battery packs

Defining your goals explicitly

After you answer these preliminary questions yourself, we shall start building the 18650 battery pack. They will help you focus on important aspects of rechargeable battery pack design.

  1. What’s the standard charge & discharge current rate?
  2. What’s the max charge & discharge current rate?
  3. What’s the minimal capacity of whole battery packs? It will determine the last time of operation?
  4. What’s battery pack size max?
  5. What’s the wire, connector information? It works for electric out.
  6. What’s the application and usage environment?
  7. Others. We can discuss later after we have the basic information it must.

Below is our lithium battery parameter and its brief explanation. Hope they can help you have a good understand of them. 

18650 lithium battery cell parameters

General physical parameters of 18650 lithium-ion battery:

Type Sealed cylindrical, rechargeable lithium-ion battery

Model – ICR18650

Nominal Voltage–3.6V

Weight — about 45g

Charging voltage–4.200±0.049V

Minimum discharge termination voltage–-2.75V

Maximum end-of-charge voltage–-4.23V

Maximum Continuous Charge Current –-1500mA

Maximum continuous discharge current–3000mA

Dimensions (including heat shrink jacket)

Diameter: d–18.0±0.2mm
Height: h-65.0±0.5mm

Minimum capacity – 2000mAh

Maximum capacity – 3400mAh

Internal resistance (20℃±5℃, measured after full charge)–less than 80mQ

Charging condition: 20℃±5℃)

Standard charging: 1000mA to 4.2V, 4.2V constant voltage to current less than 20mA

Fast Charge: 1500mA to 4.2V, 4.2V CV to less than 20mA

Use environment (recommended):

Storage-Temperature (15-35℃)  
Relative humidity (45-75%)
Atmospheric pressure (86-106kPa)

Discharge: 20 to 60°C

Standard charge: 0 to 45°C

Relative humidity <93%

Atmospheric pressure: 86 to 106kPa

Standard test environment (unless otherwise requested):

Temperature 20℃±5℃
Relative humidity 45±20%

18650 requirements for conventional chemical performance parameters (electrical performance) of lithium-ion batteries:

Appearance structure, no cracks, scratches, deformations, stains, electrolyte leakage.

Standard test strip: If there are no special requirements, the test should be carried out under the conditions of 20±5℃ (temperature) and 65±20% (humidity). The accuracy class of the ammeter and voltmeter used in the test is less than or equal to 0.5

Standard charge

It refers to charging at 0.5ItmA to a single battery voltage of 4.2V under the environment of 20±5℃ and 65±5%RH, then switching to constant voltage 4.2V charging, and stopping charging when the charging current is less than 20mA.

Fast charging

Refers to the 20±5℃, 65±5%RH environment, after charging with 1500mA constant current to the single battery voltage of 4.2V, then switching to constant voltage 4.2V charging, when the charging current is less than 20mA, stop charging.

Rated Capacity

Refers to the discharge capacity when the battery is discharged at a constant current of 0.5mA to a final voltage of 2.75V before charging under the environment of 20±5℃ and 65±5%H; after standard charging, it is left for 15 minutes; and the battery is discharged at 0.2ItmA to 2.75V. Required discharge capacity: ≥100%C5mAh.

Rapid discharge capacity

Refers to the discharge capacity when the battery is discharged at a constant current of 0.5ImA to a final voltage of 2.75V before charging under the environment of 20±5℃ and 65±5%H; after standard charging, the battery is left for 15 minutes; Required discharge capacity: ≥90%C5mAh

Cycle life

Discharge the battery as required by the standard discharge and let it sit for 15 minutes. Under the environment of 20±5℃ and 65±5%RH, after charging according to the requirements of fast charging, put it on hold for 15 minutes, and discharge with a current of 1500mA until the terminal voltage of the battery reaches the termination voltage of 2.75V. Cycle charge and discharge, when the discharge capacity of any cycle is less than 80%CsmAh, the life is terminated. The number of cycles is required to be greater than or equal to 300

-20℃ discharge performance

The battery should be charged according to the standard charging method; the battery should be put on hold for 16h~24h at an ambient temperature of -20℃±2℃; the battery should be discharged at a constant current of 0.2ImA at an ambient temperature of -20℃±2℃ to a termination voltage of 2.75V ; Discharge capacity≥60%C5mAh

Need Any Custom 18650 Lithium-ion Battery Pack?

Battery pack solution comes

Once we understand the customer’s basic parameter requirements, we can move on to the next step, dealing with the following designs and more technical points:

Cell selection
Structural design
BMS (Battery Management System) if required
Smart charger

Configuration – The configuration of the battery pack includes the number of cells and how they are connected in series or parallel, or a combination of the two configurations.

General type:

Serial – increase the voltage
Parallel – increase whole capacity
Serial/Parallel – a combination of the two

Cell Selection – By combining the specifications we listed in the first step, we can determine the best battery selection for your battery pack. Usually we offer two or three options, corresponding to different performance options and costs. At this time, the lithium battery manufacturers we choose are either LG, Samsung, Panasonic, or Chinese domestic batteries.

Structure design: our engineer will evaluate the whole size, PCM/BMS, cell layout to achieve good performance. It may use PVC shrink, mental plate or ABS housing.

BMS: the power lithium-ion battery management system can effectively monitor, protect, balance and alarm the lithium-ion battery pack, thereby improving the working efficiency and service life of the entire power lithium-ion battery pack. Lithium-ion batteries are widely used in various precision equipment due to their high operating voltage, small size, light weight, high energy density, no memory effect, no pollution, small self-discharge, and long cycle life. However, lithium-ion batteries have serious defects. In summary, there are two aspects:


Lithium-ion batteries have poor safety, and sometimes have defects such as explosions. In particular, the lithium-ion battery with lithium cobalt oxide as the positive electrode material cannot be discharged at a large current and has poor safety. In addition, almost all kinds of lithium-ion batteries are overcharged or over-discharged can cause irreversible damage to the cells. Lithium-ion batteries are also extremely sensitive to temperature: if the temperature is too high, the electrolyte may decompose, burn or even explode; if the temperature is too low, the performance of the lithium-ion battery will deteriorate significantly, affecting the normal use of the device.


The capacity fading and the inability to accurately predict the capacity of lithium-ion batteries at low temperatures make the equipment less maintainable. For long-term online meters, the battery needs to be replaced regularly, while the remote monitoring equipment work sites are scattered, and the distances between each site are long, so the battery replacement is a huge workload and high cost.

Smart charger: they are universal smart chargers. Different charging modes and corresponding algorithms can be given according to the characteristics of each battery to achieve the best charging effect. When designing a universal smart charger. It is necessary to fully consider the charging characteristics of three kinds of batteries, and give different charging modes and corresponding algorithms according to the characteristics of each battery. Rechargeable batteries have the characteristics of high-cost performance, large discharge current and long life, and are widely used in various communication equipment, instruments and electrical measuring devices.

Sampling & mass production

A sample is created after a specification sheet is drawn up, technical specifications are established, and production costs are known exactly. Sample testing is done in-house and delivered to the client’s office wherever you are.

Iterate on samples and designs until the product is finalized. Production can begin at any time after the design is complete and the pro forma invoice is signed.


Overseas 18650 Battery Cell List

LG-18650 HE225003.718.365.048.0
LG-18650 HD220003.718.365.048.0
LG-INR18650 MH132003.718.3965.1549.0
LG-INR18650 HG230003.718.3965.1549.0
LG-LG18650 MJ135003.718.3965.1549.0

Chinese 18650 Battery Cell List

BAK- 18650C422003.718.365.044.0
BAK-C18650CE30003.718 465 049 0

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FAQ of 18650 battery pack

  • Lithium-ion battery storage temperature

    The battery should be stored at room temperature, and charged to 40%~60% electric quantity.

  • How long does a 2.5Ah battery last?
    It can last 5~6 hours based on a 0.2C discharge rate. It can last 1~2 hours based on the 1C discharge rate.
  • How long to get samples?
    Generally, 7 days lead time for small quantity samples.

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