With the increasing demand of household energy management, household energy storage system has gradually become an important means to realize self-sufficiency of energy and optimize electricity consumption structure. As the core component of energy storage system, the configuration scheme of battery directly affects the performance, service life and safety of the system. Reasonable battery configuration can not only improve energy storage efficiency, but also meet the diversified needs of household electricity. This article will focus on the configuration method of batteries in household energy storage system, and introduce the key links such as battery capacity selection, group string mode, voltage matching, management system configuration and security assurance, etc, help readers fully understand how to scientifically configure household energy storage batteries.

I. Selection of battery capacity

battery capacity is one of the most critical parameters in the household energy storage system, which determines the total amount of electric energy that the energy storage system can store and release. The selection of capacity should be determined according to the household's electricity demand, load characteristics and energy storage targets.

1. Determine capacity based on electrical load
   by analyzing daily household electricity consumption and peak-valley time, the required energy storage capacity is calculated. For example, if the daily average household electricity consumption is 10kWh and the energy storage system is expected to meet the basic electricity demand at night or when power failure occurs, the battery capacity should be slightly larger than this electricity consumption, generally, a capacity of 20% to 30% is reserved as the margin.

2. Considering the depth of discharge (DoD)
   the discharge depth of the battery affects its life and safety. It is generally recommended to control the discharge depth within 80%, even if the nominal capacity of the battery is 10kWh, the actual available capacity is about 8kWh. Therefore, the capacity should be adjusted according to the DoD of the selected battery.

3. Reserve capacity to cope with future demand changes
   household electricity demand may change with the increase of lifestyle and electrical appliances. Appropriate reserved capacity can improve the adaptability and economy of the system.

II. Configuration method of battery pack string

the series and parallel modes of battery pack directly affect the voltage, current and capacity characteristics of energy storage system. Reasonable cluster configuration ensures that the system voltage matches the inverter and load requirements and meets the current requirements.

1. Serial configuration
   multiple battery cells connected in series can increase the overall voltage of the system. For example, the nominal voltage of the single battery is 3.7V. After 20 batteries are connected in series, the system voltage is about 74V. High voltage operation helps reduce current, improve system efficiency, and reduce line loss and copper consumption.

2. Parallel configuration
   parallel battery pack can increase system capacity and discharge current capability, and balance load at the same time. After multiple series groups are connected in parallel, the capacity and discharge current are superimposed. For example, after two series groups are connected in parallel, the capacity is doubled, and the current carrying capacity is enhanced.

3. Series-parallel combination
   through reasonable combination of series and parallel battery cells, the voltage and capacity of the battery pack can be flexibly adjusted to meet the design requirements of different energy storage systems. Under normal circumstances, household energy storage system electricityIt is common to press between 48V and 400V, and the design should select the appropriate group string mode according to the input voltage range of the inverter.

3. Battery type selection and voltage matching

battery types commonly used in household energy storage systems include lithium-ion batteries (such as lithium iron phosphate and ternary lithium) and lead-acid batteries. Different types of batteries have different voltage characteristics and charging and discharging performance, and attention should be paid to matching the system voltage when configuring.

1. Lithium ion battery
   lithium-ion battery monomer voltage is generally 3.2V (lithium iron phosphate) to 3.7V (ternary lithium), which is suitable for connecting to form higher voltage systems. Lithium battery has high energy density, long cycle life and wide working temperature range, which is the mainstream choice of household energy storage at present.

2. Lead Acid Battery
   the monomer voltage is generally 2V, and the number of series connections is large to reach the required voltage. Lead-acid batteries have low cost, but they are gradually replaced by lithium batteries due to their low energy density, short service life and heavy maintenance workload.

3. Voltage matching
   the battery pack voltage must match the inverter and system design voltage. If the voltage is too low, the current will increase, and if the voltage is too high, the safety of the equipment may be affected. Reasonable matching ensures efficient and stable operation of the system.

IV. Configuration of battery management system (BMS)

battery Management System is the key equipment to ensure battery safety and prolong life. BMS monitors the voltage, current, temperature and status of the battery, and implements protection and balance control.

1. Monitoring function
   collect the voltage and temperature of each cell in real time to prevent abnormal conditions such as overcharge, overdischarge and overheating.

2. Balance function
   due to the differences between the battery cells, BMS adjusts the monomer voltage through the equalization circuit to avoid excessive charging and discharging of some batteries in the battery pack and improve the overall life.

3. Protection function
   including over-current protection, short circuit protection, temperature protection, etc., to ensure that the battery runs within a safe range.

4. Communication Interface
   BMS is connected to the controller of the energy storage system through communication module to realize data transmission and remote management.

Reasonable allocation of BMS is the basis to ensure the safe and stable operation of household energy storage system.

v. Thermal management and safety measures

the battery generates heat during the charging and discharging process, and the temperature control is crucial to the battery performance and life. Household energy storage system should be equipped with effective thermal management and safety measures.

1. Passive heat dissipation
   the battery temperature is reduced by natural ventilation and cooling fin, which is suitable for small capacity systems.

2. Active Cooling
   including air cooling, water cooling and other methods, suitable for large-capacity battery pack to ensure uniform temperature and control within a safe range.

3. Safety protection design
   battery pack should have fire prevention, Explosion Prevention and short circuit prevention design; Install smoke alarm, temperature sensor and other safety devices; And equipped with emergency power failure device.

4. Installation environment considerations
   the battery should be installed in a dry, well ventilated and suitable temperature environment to avoid direct sunlight and humidity.

VI. System capacity expansion and maintenance convenience

When configuring batteries, it is equally important to consider future capacity expansion and maintenance convenience.

1. Modular design
   use standardized battery modules to increase capacity or replace faulty modules later.

2. Convenient wiring and monitoring
   reasonable wiring mode and monitoring interface are designed to facilitate daily maintenance and fault diagnosis.

3. Life Management
   regularly check the battery status, reasonably arrange charging and discharging strategies, and prolong the service life of the battery.

Battery configuration in household energy storage system is a complex process that comprehensively considers capacity requirements, voltage matching, group string mode, security assurance and management system. Through scientific selection of battery capacity, reasonable design of series-parallel combination, matching of appropriate battery type and system voltage, and equipped with perfect battery management and thermal management scheme, the energy storage system can be ensured to be efficient, safe, stable operation.