IS this an inverter or an inverter charger?
INverters may have a large "Hardening capacitor" on the input, the reasons for this are multiple on a large inverter but basically it helps with the power on surge.. Even with multi-zero gauge cable there is some "Delay" in current flow (Lag) and this capacitor helps to power the inverter during that "Delay".
With inverter/chargers there is a "Fliter" on the charger output, basically the exact same thing as above in fact it pulls double duty.
The result is a big spark when you first apply 12 volts.
In addition the remote control system draws some power (smaller spark)