As solar energy storage systems become increasingly popular, most people are familiar with common parameters of energy storage inverters. However, there are still some parameters worth understanding in depth. Today, I have selected four parameters that are often overlooked when choosing energy storage inverters but are crucial for making the right product selection. I hope that after reading this article, everyone will be able to make a more suitable choice when facing a variety of energy storage products.
01 Battery Voltage Range
Currently, energy storage inverters on the market are divided into two categories based on battery voltage. One type is designed for 48V rated voltage batteries, with a battery voltage range generally between 40-60V, known as low-voltage battery energy storage inverters. The other type is designed for high-voltage batteries, with a variable battery voltage range, mostly compatible with batteries of 200V and above.
Recommendation: When purchasing energy storage inverters, users need to pay special attention to the voltage range the inverter can accommodate, ensuring it aligns with the actual voltage of the purchased batteries.
02 Maximum Photovoltaic Input Power
The maximum photovoltaic input power indicates the maximum power the photovoltaic part of the inverter can accept. However, this power is not necessarily the maximum power the inverter can handle. For example, for a 10kW inverter, if the maximum photovoltaic input power is 20kW, the maximum AC output of the inverter is still only 10kW. If a 20kW photovoltaic array is connected, there will typically be a power loss of 10kW.
Analysis: Taking the example of a GoodWe energy storage inverter, it can store 50% of the photovoltaic energy while outputting 100% AC. For a 10kW inverter, this means it can output 10kW AC while storing 5kW of photovoltaic energy in the battery. However, connecting a 20kW array would still waste 5kW of photovoltaic energy. When choosing an inverter, consider not only the maximum photovoltaic input power but also the actual power the inverter can handle simultaneously.
03 AC Overload Capability
For energy storage inverters, the AC side generally consists of grid-tied output and off-grid output.
Analysis: Grid-tied output usually does not have overload capability because when connected to the grid, there is grid support, and the inverter does not need to handle loads independently.
Off-grid output, on the other hand, often requires short-term overload capability since there is no grid support during operation. For example, an 8kW energy storage inverter may have a rated off-grid output power of 8KVA, with a maximum apparent power output of 16KVA for up to 10 seconds. This 10-second period is usually sufficient to handle the surge current during the startup of most loads.
04 Communication
Communication interfaces of energy storage inverters generally include:
4.1 Communication with Batteries: Communication with lithium batteries is usually via CAN communication, but protocols between different manufacturers may vary. When purchasing inverters and batteries, it’s important to ensure compatibility to avoid issues later on.
4.2 Communication with Monitoring Platforms: Communication between energy storage inverters and monitoring platforms is similar to grid-tied inverters and can use 4G or Wi-Fi.
4.3 Communication with Energy Management Systems (EMS): Communication between energy storage systems and EMS typically uses wired RS485 with standard Modbus communication. There may be differences in Modbus protocols among inverter manufacturers, so if compatibility with EMS is needed, it’s advisable to communicate with the manufacturer to obtain the Modbus protocol point table before selecting the inverter.
Summary
Energy storage inverter parameters are complex, and the logic behind each parameter greatly influences the practical use of energy storage inverters.