Those power inverter thingys can be a nightmare when you use them in addition to transformers to the laptop and then production of sound.
Every thing has to be perfect, The car alternator, the car battery, the cables to the inverter are suggested to be excessive of the power required.
Watts = amps x volts
Amps = watts divided by volts
Tip, the output side of the inverter is still calculated at the 12v to obtain a correct consumption of power from the battery with a waste of 15% (that's lost in the inversion)
Anyway the problems may be resolved with a few alterations.
Renew the diode thingy on the back of the car alternator to fix the sound distortion,
increase the power cable size to the inverter in excess of required.
(sometimes its easy to directly ground the inverter negative side to metal using aluminium angle and use 2 cables on the + side)
You can access power at the starter motor as this is sometimes closer to the inverter mounting point at the floor.
Keep cables as short as possible.
Do not power inverter off the alternator directly.
Start the car and allow the alternator to recharge the battery adequately, ie 13v-13.8v before switching on the inverter.
If this fails and you still get feed back, an additional suppressor capacitor will need to be fitted to suppress the wave distortion in the power line.
Or, connect your inverter to an additional 12v battery with 10amp cable connecting it to the car battery.
Running it through another battery can often filter the fluctuation's out.
You really need a 250 watt inverter to run a 180 watt item.
True wave inverters are best but sometimes 4 times the price of synthetic or simulated wave.
As for the packaging, its their responsibility darl, a few bits of sticky or duct tape, as long as its all their they can not legally argue.
It wasn't your fault they packed it that way.
All the best and be carfull, there is enough power in a car battery to kill you twice before your dead, Whooooaagh! true!
Lah da de dah da The eletricions jingle goes:,
The red one connects to the red thing.
The black one connects to the whatsy thing,
The true thing inverts the coloured thing,
and 120 volts comes out!
lah dah de dah da da daaaah!
LOL its all fun.