Yes,the following is the calculation of fuse ampere.

Continuous power of the inverter ÷ Lowest input voltage =Fuse ampere,  

e.g.

 3000W 12VDC version: recommed a 300Amp fuse (3000W÷10VDC=300Amp)

 3000W 24VDC version: recommed a 150Amp fuse (3000W÷20VDC=150Amp)

 3000W 36VDC version: recommed a 100Amp fuse (3000W÷30VDC=100Amp)

 3000W 48VDC version: recommed a 75Amp fuse (3000W÷40VDC=75Amp)

This is normal, and it is not that the inverter is malfunctioning. The inverter has built-in large capacitors, a very small amount of power is still stored inside. When the battery cable is connected to the input of the inverter, sparks may appear, which is a discharge process.Please feel free to use it

e.g 3000W 12VDC version

1). Pls check if there is a fuse or breaker installed in your system.Generally,we recommend that a 300Amp fuse be installed between the inverter and the battery.If the fuse size is too small, it will limit the input current.

2). Pls check if use standard cables all . If 4 cables, please use them all, or the output will only be about a half. If you use your own cable, please make sure that the cable specification is larger than AWG 4, and if the length exceeds 24 inch, please thicken the cable.

Note that there is a voltage drop between the battery and the inverter. The thinner and longer the cable, the greater the voltage drops.

3). Pls check if the battery capacity is too small .We recommend connecting to a battery system 300AH for a 3000-watt 12VDC inverter. When the DC LED reading drops while the load is running, it is likely that your battery capacity is too small to supply power to the load. Please try to add other batteries to your previous battery system.

Pls fully charge the battery before installing the inverter . There are some large capacitors built into the inverter, so it may be in the low-voltage protection or even unable to turn on when the battery power is low

Compressor are inductive in nature and would be a hard load on the inverter.The vast majority of the refrigerator’s power consumption takes place in the compressor, which kicks the instantaneous power in startup phase to 3-5 times ,or even 7 times bigger as its working power. .If you want to power up a refrigerator, we suggest you use 7 times higher power inverter. Please check that the load within the allowable range