Individual Soldier night vision instrument is an indispensable equipment in modern military, law enforcement and outdoor activities. Its performance and endurance directly affect the use effect. As the core power supply part of night vision instrument, batteries play a key role in the stable operation of equipment. 7.4V lithium battery has become the most common power supply scheme for single-soldier night vision instrument due to its small size, high energy density and rechargeable characteristics. This article will introduce in detail the design scheme of 7.4V rechargeable lithium battery, including the battery structure, material selection, protection circuit design, charge and discharge management, installation interface and other key contents to help readers fully understand and apply the battery scheme.

I. Basic overview of 7.4V lithium battery

1. 7.4V voltage source

7.4V lithium battery usually consists of two 3.7V lithium ion or lithium polymer battery cell in series. The nominal voltage of each cell is 3.7V, the full charge voltage is about 4.2V, and the total voltage after series connection is 7.4V (nominal) or 8.4V (full charge). This voltage level is suitable for the power supply requirements of most individual soldiers night vision instrument, which can not only ensure the normal operation of the equipment, but also give consideration to the volume and weight.

2. Advantages of lithium battery

• high energy density: Compared with traditional Ni-MH or Ni-Cd batteries, lithium batteries have higher energy density and longer endurance.
• No memory effect: The number of charge and discharge is large, and it can be charged without full discharge.
• low self-discharge rate: The power consumption is not lost for a long time.
• Lightweight design: easy to carry, suitable for individual equipment needs.

II. Structural design of 7.4V lithium battery

1. Select cell

commonly used cell specifications include 18650 cylindrical and polymer soft pack batteries:

• 18650 cylindrical cell: large capacity, long cycle life, high mechanical strength, easy to standardize production and replacement.
• Polymer soft bag cell: flexible shape, can be customized according to night vision instrument internal space, light weight, but high requirements for packaging and protection.

The choice should be based on the night vision instrument space size, weight limit and battery life.

2. Battery assembly method

3. Connection terminal design

the battery pack needs to be designed with standardized interfaces to facilitate quick loading and unloading. Common interfaces include plug-in, shrapnel and plug-in connectors to ensure good contact and durability.

III. Protection circuit design (BMS)

lithium battery pack must be equipped with a battery management system (BMS) to ensure safety and prolong battery life. The main functions of the BMS include:

1. Overcharge protection

when the single cell voltage exceeds 4.2V, BMS automatically cuts off the charging circuit to prevent potential safety hazards caused by overcharging of the battery.

2. Over-release protection

when the voltage of cell drops to about 2.5V, the BMS cuts off the discharge power.Road, avoid battery over-release damage cell.

3. Overcurrent protection

prevent short circuit or abnormal discharge current and protect the safety of batteries and equipment.

4. Temperature protection

monitor battery temperature through temperature sensor to prevent charging and discharging under high temperature or low temperature environment and ensure safety.

5. Balanced charging

charge the series cell evenly to avoid the voltage inconsistency of the monomer cell and prolong the overall life of the battery pack.

IV. Charge and discharge management scheme

1. Charger specification design

the charger must match 7.4V lithium battery pack, and usually adopts constant current and constant voltage (CC/CV) charging mode:

• constant current stage: the charging current remains stable and the power is quickly replenished.
• Constant pressure stage: the voltage is kept at 4.2V × 2=8.4V, and the current decreases gradually to prevent overcharging.

The charger should have over-temperature, over-current and short-circuit protection to ensure charging safety.

2. Discharge management

night vision instrument the internal circuit design must match the 7.4V battery voltage range to ensure that the equipment can still operate stably when the battery voltage drops. The low voltage alarm circuit prompts the user to change or charge in time.

V. Battery installation and interface standardization

1. Compatibility design

the 7.4V lithium battery solution should take into account night vision instrument interface compatibility of different brands and models, and adopt industry common interface standards to facilitate the general use of military and civil equipment.

2. Quick disassembly design

the design of the battery box should be convenient for individual soldiers to quickly change the battery, and the snap-on or sliding structure should be adopted to improve the actual combat efficiency.

3. Protection performance

the battery box must have waterproof, dustproof and shockproof functions to meet the needs of complex environments.

VI. Performance optimization and testing

1. Capacity and endurance test

through the actual load test, verify that the battery capacity matches the endurance requirement of night vision instrument to ensure that it meets the requirement of continuous use for several hours.

2. Charge and discharge cycle life test

simulate the actual charging and discharging environment, evaluate the cycle times and capacity retention rate of the battery, and ensure the stability of the battery for long-term use.

including short circuit, overcharge, overdischarge, overheating and other safety tests to ensure that the battery scheme meets military safety standards.

VII. Case demonstration

A certain model of individual soldier night vision instrument adopts customized 7.4V 2600mAh polymer lithium battery pack, built-in BMS protection circuit, and supports standard USB charging interface. The battery box adopts waterproof design and is equipped with quick buckle interface. Users can quickly change the battery in tactical environment. After several rounds of experimental tests, the battery pack meets the demand of night vision instrument continuous working for more than 8 hours, with excellent safety performance and highly recognized by users.

7.4V Rechargeable lithium battery with its advantages of small size, high energy density, good safety performance and convenient charging, the scheme has become the most common power supply scheme for single-soldier night vision instrument. Through reasonable cell selection, perfect protection circuit design and interface standardization meeting actual use requirements, this scheme can provide stable and lasting power support for night vision instrument, ensure the efficient conduct of individual combat and operations.