[Mobile-Portable] HF mobile newbie question

[Scott Oakland]

Hello:

I have been trying to connect a Yaesu FT101ZD (has one 6146B final) to 
my car battery via the cig. lighter and a Portawattz 300 W inverter 
(rated at 30A max) with no success. When I turn on the rig, after a 
short time , the inverter alarm starts beeping and power begins to shut 
down or be intermittent. Is it because my cig lighter outlet is rated 
only for 10 amps (the rig draws up to 20)? Would a portable 
powerpack-type unit instead of the car battery be better? I don't relish 
having to connect directly to the car battery. I want to go portable to 
islands in the area (IOTA / USI), and would like to get this rig on as I 
don't have the $ to buy a dedicated mobile rig.

Tnx
Scott W1AL