Submitted: Friday, Apr 16, 2004 at 14:36
ThreadID: 12102 Views:1948 Replies:9 FollowUps:7
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Hi everyone, we are going to buy an inverter, i've done an archive and found the pro's and con's. What i need to know is what wattage should i get, looking at the archive 300w seems to be the most common, we will be running a tv, laptop and a fridge but only when we are driving not when we're stopped, it is a 3 way and draws to many amps, not much else.

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Reply By: Davoe - Friday, Apr 16, 2004 at 15:12

Friday, Apr 16, 2004 at 15:12
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
AnswerID: 54543

Follow Up By: Baz (NSW) - Friday, Apr 16, 2004 at 15:43

Friday, Apr 16, 2004 at 15:43
The fridge is run on gas when we are camped,only running off the inverter when on the move, our tv is old and can't get 12v plug for it we're getting one made up, so in the meantime going to run it off inverter, the laptop, well, the other half won't run it off the cig lighter she does'nt trust the current, spiking or something, not electronicly minded sorry.

FollowupID: 316178

Reply By: Wombat - Friday, Apr 16, 2004 at 15:43

Friday, Apr 16, 2004 at 15:43
I humbly suggest that you DON'T run your fridge on gas whilst travelling.
AnswerID: 54544

Follow Up By: Davoe - Friday, Apr 16, 2004 at 16:44

Friday, Apr 16, 2004 at 16:44
do it all the time although i do have a campervan with proper ventilation for it. i also have a 25 - 30cm b/w tv which is over 25yrs old (dont build em like that any more) which I dont actually know hw much power it uses as I have never managed to flatten a battery with it. After a closer look at his rig pic I guess the gas bottle for the fridge would not be outside as in a camper, so right you are!
FollowupID: 316185

Reply By: Member -Bob & Lex (Sydney) - Friday, Apr 16, 2004 at 16:14

Friday, Apr 16, 2004 at 16:14
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
AnswerID: 54548

Reply By: Rosscoe - Friday, Apr 16, 2004 at 16:28

Friday, Apr 16, 2004 at 16:28
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.
AnswerID: 54553

Follow Up By: Baz (NSW) - Friday, Apr 16, 2004 at 18:02

Friday, Apr 16, 2004 at 18:02
Only running fridge off inverter when traveling, when we get one, at the moment it runs directly off battery only when traveling. Fridge runs on gas when camped for the night or nights, my question was what size inverter should i get, 300w, 400w, 500w, ect, ect. The inverter is mainly for running other elec items eg, tv, microwave, lights, laptop, ( small elec items ) not all at once.

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Reply By: Nomad - Friday, Apr 16, 2004 at 20:01

Friday, Apr 16, 2004 at 20:01
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.


AnswerID: 54588

Follow Up By: Nomad - Friday, Apr 16, 2004 at 20:06

Friday, Apr 16, 2004 at 20:06

Don't mean to be rude mate, but why do you want to take a microwave and et al when you are goiing camping???? I thought camping was a bit about getting back to nature. Nothing like a roast lamb dinner cooked in a camp oven on an open fire. No offence meant.


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Follow Up By: Baz (NSW) - Friday, Apr 16, 2004 at 21:21

Friday, Apr 16, 2004 at 21:21
The microwave is not my idea, i'm happy with a fire or gas stove. SHMBO wants to take the home kitchen away with us. When the camper is fitted out it will have a battery and so on, going to the show tomorrow to pick up a few things, 12v and 240v in/outlets, dual batt system and other stuff.

FollowupID: 316271

Reply By: Member - Oskar(Bris) - Friday, Apr 16, 2004 at 23:00

Friday, Apr 16, 2004 at 23:00
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
AnswerID: 54639

Reply By: rolande- Friday, Apr 16, 2004 at 23:17

Friday, Apr 16, 2004 at 23:17
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.
AnswerID: 54644

Reply By: Member - Pesty (SA) - Saturday, Apr 17, 2004 at 00:58

Saturday, Apr 17, 2004 at 00:58
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
AnswerID: 54653

Follow Up By: Baz (NSW) - Saturday, Apr 17, 2004 at 11:33

Saturday, Apr 17, 2004 at 11:33
Thanks Oskar, Rolande and Steve, pure sine wave is what we're looking at and about 300 to 400 watts, the car battery is never used when camped only when traveling. I've been trying to tell her that a microwave was not a good idea, our fridge is a electrolux upright caravan type, so it draws alot of amps, hence the need for a inverter, i figured that while on the move 240 from the inverter would be better than 12 and the alternater will keep the battery charged up, if we used a battery to run the fridge it would flatten the battery in about 1 to 3 hours.
One dual batt with inverter coming up

Thanks again fella's.
FollowupID: 316330

Reply By: ThePublican - Saturday, Apr 17, 2004 at 12:57

Saturday, Apr 17, 2004 at 12:57
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.
AnswerID: 54675

Follow Up By: Baz (NSW) - Saturday, Apr 17, 2004 at 19:06

Saturday, Apr 17, 2004 at 19:06
I should of explained it's not a dual batt like in a vehicle, it's the car batt and 1 or 2 batts in the camper set up similar, i did'nt want to put a batt in the back of the car. the camper is only new so i'm setting it up one thing at a time, eventually it will be the way we like, he say's hopefully !!
I'll do that archive search on heat extraction, thanks for that.

FollowupID: 316368

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