INVERTERS

run your 3 way fridge off of gas - they dont use much, get a 12v tv they dont draw much battery power and plug your laptop into the cig lighter

I humbly suggest that you DON'T run your fridge on gas whilst travelling.

I don't think a 300 w will have enough power for the fridge or tv . Have you checked the power draw on them. Ive run our laptop off the cig lighter for years with no problems using a Targus transformer

I assume you do not intend running all at the same time.

I agree that you should run the fridge directly from the car's 12Volt system while driving, NOT on gas. Is there a reason you are contemplating running through the inverter? 3-way fridges draw a fair amount of current on straight 12V DC and I think your 300W inverter would not handle the load.
If its an old TV it too probably draws more than the modern units.
I just bought a 300W inverter from Dick Smiths and it's rated at 300Wats at about 13 Volts at 12.65V of a fully charged battery I need to turn the inverter/TV on and off several time to get the picture tube warmed up.

A 300w inverter will handle the fridge no worries. However, I don't believe you need to do it. Run it straight from your cars 12v system. I have done it both ways extensively and really there is no difference.

There was some scuttlebut about the 12v being inefficient but I have not found this to be the case. Over Easter we ran the Engel (I know not 3 way) on the 12v on the way home, about 200k, and almost frooze the contents (including the beer).

TV and laptop should run of the inverter but would be better off the 12v. Of course a dual battery system would be a better idea so that you always have a good cranking battery available to start your car.

Cheers

Nomad

Baz
I actually found that my 3 way ran better off the inverter on 240V than on 12V in the back of my vehicle. I checked it with the digital thermometer.
I really only use the inverter for running the laptop and charging batteries for cameras etc. as we use the Evakool fridge for touring and the Chescold for camping.
So how 'bout that
Cheers
Oskar

Baz,
I assume that if you are worried about current spikes etc. in the laptop then you would have decided on a pure sine wave inverter rather than the cheaper square wave type.
Rolande

Hi Baz
I used a chesclod freezer for years and it works much better on 240v than 12v as it is hard to get good connections that can handle 12w dc continuesly. From memory it draws about 75w ac your tv about the same, 75w to 100w ac not sure about the laptop but I suspect it would be less so add all the wattages together and factor in a safety margin of about 100w and buy your inverter. You will not be able to run your microwave on it unless you get about 1200w unit and these are big, expensive and heavy on battery supply as you could only use it while stationary, make a deal with SWMBO and leave it home. I would go for about 400w from what you are saying and if the need arises you could run all 3 at the same time. I have a 300w unit which I dont use a lot mostly for camera chargers etc and on a hot night we will run a small fan all night but it works fine.
Have a good day at the show

Cheers Steve

Baz,,have used a 3 way for years,and true they use bulk amps on 12v ,you can make them more efficient by fan forced heat extraction [check archives],,am very interested in where you plan to fit your 2nd battery as I could not fit one under the bonnet in our Explorer,had to cut down a drawer in the storage unit and have 2nd battery there [rotronics controlled],,now use a total of 5 bats, 2in vehicle +3 in camper trailer [1 delcor marine for lighting + 2 century deep cycle for 80lt waeco] gives upto 5/6 days at 80%. battery reserve.