That's not a lot of load. Cell charger and Tomtom together may draw an amp or two. Inverter, now, may draw as much as 40, if straight math holds. 450w @ 120v, or a little under 4amps, and if you do a straight transform thats a little under 40a at 12v. This gets a little screwed up as one is ac and the other dc, so one is wrms amps and the other is constant current. At least this is the way the 'lectron 'splained it to me the last time I caught one and got it to talk... 'Lectrons are devious, however, and may have been foolin' old Eddy....

Not responsible for advice not taken...