Inverter.

It might help if you'd tell us what you're really trying to do.  There may be alternative solutions.  Most phones and laptops can charge from 12v DC, or a little 200w inverter is plenty for them.  It will also power the television.  Coffee makers and hair dryers are generally beyond the limits of battery powered inverters.

VOISJ is right -- the pod doesn't have an inverter.  It's converter takes 120v AC shore power and converts it to 12v DC to run 12v things in the pod and to charge the battery.  And of course, if you have shore power you have all the AC and DC power you should need.

I suspect you meant watts when you asked about increasing the volts.  More watts would be nice, but, no they can't be increased.  As for volts, the only things you want are nominal 120v AC or nominal 12v DC.

TT

400 watts is probably about the most you can sustainably get out of an inverter on your TV, and that only while it's running.  People hook up bigger inverters, and they may work for a while, but they'll suck a battery down quickly, especially if the engine/alternator isn't running.

I have a 12,000 lb winch on my truck and it sucks the juice.  It can use up to about 4000 watts.  To do that for more than about 10 or 20 seconds the engine has to be on.  To do it for 30 to 60 seconds you have to have your foot on the gas.  (My old Bronco had a manual throttle you could pull out and set!)  With all that, after a couple of minutes of winching something substantial you can watch the battery level going down.  Like most stock vehicles, I only have a 100 amp alternator.  You can buy 130 amp or even 200 amp alternators, but at that point, for camping purposes, you're probably better off with a generator.

TT