Off-grid inverters have overload capacity. 

For example, a 3kW off-grid inverter can support a 1kW motor to start, and the maximum starting instantaneous power can reach 6kW. Some people think that the energy of this instantaneous power should be provided by the inverter external In fact, the energy in milliseconds can not be provided by the battery whether the photovoltaic or the battery, but the inverter can provide it, and there are energy storage elements in the inverter—capacitors and inductors, which can provide instantaneous power. The same cable is used for charging and discharging the battery, so when designing, the actual charging and discharging current should be calculated. Which one is the largest, choose which one, such as a 5kW inverter with 4kW components, with a 3kW load, the battery 48V600AH, the maximum charging current of the inverter itself is 120A, the maximum charging current of the photovoltaic is 80A, and the maximum discharge current of the battery is 65A when the load is maximum. 16 square meters, if the photovoltaic and mains can be charged at the same time, the current can reach 120A, at this time the cable needs 25 square meters.

When the photovoltaic output and the load power are similar or slightly larger, the photovoltaic current can be directly supplied to the load without passing through the battery, and the off-grid system has the highest efficiency; when the photovoltaic power generation and the load are not used in the same time period, such as photovoltaic power generation during the day, the load uses electricity at night At this time, photovoltaic power generation must first enter the battery and then enter the load, and the efficiency of the off-grid system is low. 

The cable of the battery should be designed according to the maximum charging and discharging current of the battery. The same inverter has different currents in different applications and needs to be calculated differently.