In home backup power scenarios, 20kW-class solar cells (it should be clarified first: "20kW" is often easily confused with "power" and "capacity"—home backup focuses more on the capacity unit kWh, such as a 20kWh solar cell; if it refers to "power", it refers to the battery's maximum discharge power, such as 5kW/10kW, which needs to be matched with capacity) are core equipment for responding to power outages and supplementing photovoltaic self-use, and are particularly suitable for households with high electricity demands. The following explains the core positioning, key features, selection considerations, and usage precautions:

　　1. Core Positioning: A "Reserve of Energy" for Home Backup Power

　　A solar cell with a capacity of approximately 20kWh (combined with a photovoltaic panel and inverter) primarily addresses two household needs:

　　Power outage emergency response: Continuous power supply for critical household loads, such as refrigerators (approximately 1-2kWh per day), central air conditioning (approximately 1-2kWh per hour), lighting (approximately 0.5kWh per day), router/phone charging (approximately 0.3kWh per day), and water heaters (approximately 2-3kWh per day). If the total power of critical loads is approximately 3kW, a 20kWh battery can provide 6-8 hours of continuous power (extended to 1-2 days if only low-load loads such as refrigerators and lighting are maintained). Photovoltaic Consumption: If a household already has a photovoltaic system, any unused daytime solar power can be stored in batteries, avoiding grid-connected power curtailment (grid-connected electricity prices are low in some areas). This stored power can then be used at night or on rainy days, reducing household electricity bills.

　　II. Core Features: Key Indicators for Home Use

　　Home backup battery requirements for safety, stability, and lifespan are far higher than those for commercial use. Currently, the mainstream choice is a 20kWh solar cell using lithium iron phosphate (LiFePO4) cells. Its core features are as follows:

　　High Safety: LiFePO4 cells offer exceptional thermal stability and are resistant to fire or explosion due to overcharging, short circuiting, or impact. They are the preferred choice for enclosed environments in homes, such as balconies and garages. (Compared to ternary lithium batteries, they offer significantly higher safety.) Long cycle life: Home backup batteries don't require daily full charge and discharge. LiFePO4 batteries have a cycle life of up to 3,000-6,000 cycles (assuming 100 cycles per year, a lifespan of 30-60 years), far exceeding lead-acid batteries (approximately 500 cycles, a lifespan of 3-5 years), providing better long-term cost-effectiveness.

　　Wide temperature adaptability: Most products support an operating temperature range of -20°C to 55°C. While discharge efficiency may decrease slightly in low temperatures in northern winter (e.g., approximately 80% efficiency at -10°C), models equipped with a low-temperature preheating function can meet household needs in most regions.

　　High charge and discharge efficiency: High-quality products can achieve a charge and discharge efficiency (DC-DC) of 90%-95%. This means that for every 10kWh of photovoltaic power generated, approximately 9-9.5kWh can be stored in the battery, minimizing energy loss. Low maintenance: No need to refill or refill lead-acid batteries. Daily maintenance requires only maintaining a well-ventilated and dry environment, and regularly checking for loose connections (every 3-6 months).

　　III. Key Selection Considerations: Five Key Considerations to Avoid Mismatches

　　Calculate "critical household loads" first, then determine capacity/power.

　　Prioritize the power consumption of equipment that must be maintained during a power outage (e.g., "refrigerator 0.3kW + lighting 0.1kW + router 0.05kW," for a total of 0.45kW) and the duration (e.g., if you want a 24-hour power outage). Required capacity = power × time ÷ discharge efficiency (approximately 0.9), i.e., 0.45kW × 24 hours ÷ 0.9 = 12kWh. If you have central air conditioning and an electric water heater, add additional capacity to avoid blindly selecting 20kWh and wasting money.

　　Ensure that "Battery Power" matches "Load Power": If your home has a 1.5kW air conditioner, the battery's maximum discharge power must be ≥1.5kW (it's recommended to leave a 20% margin and select a model with a discharge power of ≥1.8kW). Otherwise, overload protection will be triggered, preventing high-power devices from starting.

　　Compatibility: Compatible with PV Inverters/Grid Switching Devices

　　Home backup systems typically combine PV panels, an energy storage inverter, and batteries. Ensure the battery's voltage specifications (e.g., 48V/110V/220V) and interface type (e.g., RS485/CAN communication interface) are compatible with the inverter (for example, the inverter must support "off-grid mode" to switch to battery power during a power outage).

　　If dual-mode "grid-connected + backup" is desired, select an energy storage inverter that complies with local grid standards (e.g., China's GB/T 34131 standard) to avoid grid connection failure or switching failures during a power outage. Installation Space: 20kWh Battery Volume and Placement Requirements

　　A 20kWh LiFePO4 battery pack (using a 48V system as an example, approximately 416Ah) typically has a volume of 0.5-0.8 cubic meters (similar to the size of two or three vertical water dispensers) and weighs approximately 200-300kg.

　　The installation location must meet the following requirements: good ventilation (to avoid heat accumulation), load-bearing capacity (balcony/garage floor load ≥ 50kg/m2), and away from fire/water sources (for example, installation near kitchens and bathrooms is not recommended). Some products support wall-mounting (saving floor space), but the installation method should be confirmed in advance.

　　Smart Management: Convenient Monitoring and Control

　　Preferably choose models with "app-based remote monitoring" to view real-time battery charge, charge/discharge power, and remaining battery life. You can even remotely set "peak/off-peak charging" (e.g., charging from the grid during off-peak hours at night and using battery power during the day) for enhanced convenience. It should support intelligent protection features such as overcharge/over-discharge protection, overtemperature protection, and short-circuit protection to prevent damage from abnormal operating conditions.

　　Brand and Warranty: "Reliability Guaranteed" for Home Backup

　　Avoid unbranded "assembled batteries" and prioritize brands focused on energy storage (such as CATL household energy storage batteries, BYD, and Sungrow). These products offer more consistent cell quality and more mature circuit protection designs.

　　Pay attention to warranty terms: Reputable products typically offer a 5-10 year warranty or a commitment of "capacity retention ≥ 80% after 3,000 cycles" to avoid unreliable maintenance.

　　IV. Usage Precautions: Extending Lifespan and Ensuring Safety

　　Avoid "Deep Discharge": Try not to use the battery below 20% (retain at least 20% remaining charge). Deep discharge accelerates cell aging and shortens lifespan. (For example, for a 20kWh battery, it's recommended to recharge when the charge drops below 4kWh). Regularly activate the battery: If the battery is not used for an extended period (e.g., more than one month), maintain a battery charge between 50% and 80% and charge and discharge it once a month to prevent the battery from going into dormancy due to low battery life.

　　Professional Installation: Do not perform wiring yourself: Batteries involve high-voltage circuits (e.g., 48V and above). Wiring and debugging must be performed by an engineer with "Energy Storage System Installation Qualification" to avoid the risk of electric shock or short circuits.

　　Pay attention to ambient temperature: Although LiFePO4 has good temperature resistance, prolonged use in environments above 40°C or below -10°C will accelerate capacity degradation. It is recommended to install a cooling fan (in high-temperature regions) or insulation (in low-temperature regions) at the installation location.

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