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nissan
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Discussion Starter #1
Hi All

So I have a 1200w inverter sitting here and want to put it in the
trol..... BUT what size fuse/circuit breaker do I use???

After googling I have read some say 125A so this has blown me away.
Thought I had best ask..
 

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just a good guy.
2009 gu ute
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9,512 Posts
I have a 2500w inverter. no circuit breaker or fuse between it and battery. just use the inbuilt inverter fuse.
 

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nissan
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I have a 600watt inverter in the camper trailer and the manufacturers spec is for a 100amp fuse.
For a 1000w it is a 150 amp fuse.
Definitely fuse it unless you want a fire in your car if something goes wrong.
If it were me I would install 150amp fuse minimum with at least 32mm2 size cable if it is within 3 meters of the battery or go up in size if the inverter is going to be in the back and away from battery
 

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nissan
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My guess is that your Inverter is 1200W at 120V ?

1200/12 = 100Amps


The fuse must be rated for more than the inverter will draw at full load, and less than the feed wire can safely carry.
The inverter instructions should tell you what to have for a fuse at the battery.
You need to look at a wire chart to see what your #2 wire can carry, based on wire size, and length of run.

The fuse at the battery is there to protect the circuit, not the inverter.
 

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Hi bongo, you need to fit a fuse or circuit breaker with at least a 50% greater current rate than the maximum output of the inverter.

In your case, with a maximum inverter output of 1,200 watts, if your battery is low, the inverter will pull much higher input currents, so you need at least a 150 amp fuse/CB and your cabling needs to have a CONTINUOS rating of at least 25% greater than the fuse/CB.

So you need a 150 amp fuse/CB and 1B&S ( 40mm2 ) cabling, which has a 100% cycle rating of 210 amps.

Bongo PLEASE NOTE, these figures are for reasonable quality inverters.

There are some pretty poor quality products out there and for an example, there is a 30 amp inverter that is lucky to supply 26 amps yet at low input voltage, draws just over 50 amp.

So with such poor quality gear like this, you would need to have input protection of better than 90% greater than the output current.

And you would need much thicker cabling as well.
 

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nissan
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Discussion Starter #7
Thanks to all that have replied.... What I should have given all in the start was the
details of the unit i was given.

It is this one:HERE


The reported specs are :

DOSS PIN1200 - 1200W 12v DC - 240v AC INVERTER - TVs, Computers, Radios, & Ovens


Transforms 12V DC into 240V AC
For use on notebook computers radios, TVs,VCRs, lamps, ovens etc.
Input voltage; 10-15V DC.
Maximum input current: 130A
Standby input current: 0.4A
Output: 240V ~ 50hz
Output power-continuous: 1200W
Peak: 2400W
Efficiency: 85%-90%
Overload Protection
Polarity Protection by 35A fuse
Dimensions (LxWxH): 320 x 210 x 85 mm
Weight: 3.9kgs
> Optional remote control also available
 

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Y61=WIN
nissan
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Drivesafe is on the money. They arent 100% efficient devices. You need to allow for losses to heat and so on in providing the output power. Your going to put more input power for a given output power. Not fusing it is silly. I see the claimed efficiency of your model is at worst 85%.

He also makes a good insight about continuously rated cabling - inverters draw so much energy you dont want to add to that by heating up the dam power cables :)

Personally I wouldnt implicitly trust the OEMs stated figure on efficiency and amp draw, I'd fudge over those for safety factor, its not like the extra weight of bigger cables is going to matter in this 4wd application.
 

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Hi again bongo and as nullack posted, the figures used to advertise these things may look good but they are not relevant with out a few other factors.

For instance. The efficiency figures need to have the voltage listed, at which this efficiency level was achieved.

My guess is that it was at at least 14.5v.

This is all good and well except as the input voltage drops, so does the efficiency of any inverter.

Then there is the 130 amps maximum input.

Well they also state that the device can be operated over a voltage range of 10 to 15v.

I would bet that at 12v, and pulling maximum output, that inverter would be operating at it’s maximum input current, and your efficiency would be below 70% at very best.

Anything below a 12v input voltage and you will have to reduce the maximum output load.

BTW, most inverters, not just this one, are marketed this way.
 
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