My Motor Trend Inverter 400 watt give's me a fault light upon start up. The fuse is good

The lighter socket power cord has a 15 amp fuse. The cable with the battery clamps do not have fuse protection.

Hello, the answer is no. This inverter will work with a pump that below or about 400 watts power for operation. I notice it says that the inverter 400w/800w. The 800 watts is the surge required to get an electric motor to run. On a single phase motor (120 AC) and it take 4 amperes to operator this motor. But to start the it will 12 amperes to start it. This is one reason why on a lot of electrical motors there will be a big tube or can, this is the starting capacitor, it stores energy in form of current (amperes) to drop across the windings of the motor when it starts. If some electric motors didn't have this capacitor. The most likely scenario would be tripping a breaker because it drawing to much current.


Now, for you problem. Example of Power and the unit of the formula is V (volt), R (resistance) I (current) P (power) Ohm's states that :




Now Power would be stated: P = V times(x) I. Therefore in your case, if the pump at normal operation is drawing 4 amps of current for operation pumping water. The power factor would be 120 V AC (house voltage) times (X) I (current) which 4 amps. So here is what you have: P = 120 X 4 equal= 480 watts.

Therefore, your inverter will not work because it operating at 80 watts more than the power inverter can deliver which is 400 Watts.



If you need to purchase a new power inverter, remember always take into account the Amperes required for operation. Just by the simple Ohm's Formula. Best of Luck. GB....stewbison
son

Hi Gena, the inverter is a 400 watt unit. This is not a rating for a continuous load. You do not mention which fuse is blowing. This could be the fuse in the inverter or the cigarette lighter (power source) fuse. In either case, a fuse blowing could be a short circuit, something in the inverter shorted, or too much load. I am going to look at the too much load side of things. Not knowing how many laptops are being used, with the inverter if you have a 20 amp fuse in the cig lighter, this will allow you 20 amps X 12 volts = 240 watts. I would not run the inverter over 240 watts because of overheating issues. So, 240 watts will run 3 laptops. Just the laptops. Most laptops draw around 70 watts. check your power supplies on them to find their rating. If you exceed the 240 watts by combining the ratings, then you can expect trouble with your inverter. It will give 400 watts, but this is a temporary condition only. Another inverter will be needed or a larger one installed and it being connected directly to the battery (with a fuse of sufficient size installed). You could also (let us say there are 6 computers) charge and run 3, and the other 3 are running on their batteries. After an hour, switch so that the 3 running on batteries now are charging as well as running. The other 3 are now charging.
I hope this helps. If you have any other questions please provide additional information. Such as the size and location of the fuse blowing. The laptop power supply ratings.
thank you

If the inverter is blowing the fuse immediately upon plugging in the inverter (before you even plug something into the inverter) you most likely have a short in the 12V power cord. If you have an Ohm meter, you should be able to check the resistance across the two contacts on the 12V plug of the power cord. Wiggle it around some. If you get a very low reading, and especially if it's intermittent, you have a bad cord, which should be pretty easy and cheap to replace. My experience with these cords has been that their quality is pretty poor.
If that is the problem, maybe you can cannibalize a cord from an old CB radio, but here's a fairly heavy duty one on Amazon (they don't give an amp rating though) http://www.amazon.com/Truckspec-TSPSCBH-2CP-12-Volt-Platinum-Replacement/dp/B001JT5QF0

I ask a friend

Try FASTENAL . Should be a store close to you. GOOGLE for a location.. Also, might try a Radio Shack although I have NOT had much there when I was looking for nuts and bolts...

It sounds like the fuse that protects you cigarette lighter is blown.

After you have replaced the fuse, check the voltage again. 0.015vdc would not have powered anything that in manufactured to operate on 12vdc.

When powering anything over about 250W, I would suggest connecting directly to the battery to avoid overloading the lighter circuit.

Restating the question - 400 watt inverter is turned on and running with the vehicle turned off.
After starting vehicle the red light of the inverter is on with no power output from the inverter.
If you turn the inverter off then on inverter operates normally.

Solution - this is normal operation - my inverter does the same thing. When you start the vehicle
it draws a lot of current from the vehicle battery which causes a drop in battery voltage. Most inverters have a low voltage input safety and will fault the device.'

If the problem is turn on inverter then the red light starts flashing... I am thinking you
have the same problem as the one I replaced - it broke... I am sure some capicator
or other component in the circuit failed... My solution was to purchase a new one...

Assuming you are testing alternating current and not direct current that sounds quite normal. Plug with confidence. You are using equipment designed for 110v-120v and you're getting 113.8v where it matters most. Higher voltage to ground is nothing unusual, that's just how this inverter is designed.

If you want to get more precise, figure out everything in terms of power (watts).

Basic electrical rule 1, 2 and 3:

voltage x current = power

or re-arranged:

current = power divided by voltage

or re-arranged:

voltage = power divided by current


For example, 12V X 2 amps = 24 watts.

or another example, 400 watts divided by 120 Volts = 3.33 amps

A 55W headlight that uses 12V would draw 55 /12 = 4.6 amps @ 12V

A 55 watt light bulb in a lamp at home would draw 55 / 120 = 0.46 amps @ 120V


As the previous post mentioned, inverters are not perfect when convertering 12V into 120V. If the converter consumes 1000W from the 12V battery, then a 90% effecient converter would generate 900W of 120V AC power best case. The other 100W is lost primarily as heat.

The other thing that gets tricky is that these ratings and the formula above are used for resistive loads, like light bulbs or hair dryers. Anything with a motor or transformer is considered an inductive load and can get much more tricky to calculate.

Consequently you need to give your self a safety margin when figuring out how big an inverter you need.

How does work in a practical sense?

Lets say you want an inverter for TV, DVD and Sat. Receiver. Look at the back of TV or in the manual. It should say how many watts it consumes. Lets say it is 400W. The DVD might be 100W and the Sat. receiver 50W - just as an example.

400 + 100 + 50 = 550 Watts. (just as an example)

You might think, well no problem, I'll use a 600 Watt inverter and have 50 watts left over. Depending on your inverter, that 600W might really be 600 x 90% effecient = 540 Watts of AC, less a 20% margin of error for the inductive transformers in the electronic of the TV, DVD and Sat. receiver 540 - 20% = 432 Watts.

Now you can see your 600 Watt inverter isn't big enough to do the job.

If we really need 550 watts of AC, add 10% to make up the effiency loss, then add a safety margin for inductive loads.

550 + 10% = 605 + 20% = 726 Watts.

Sounds more like an 800W inverter fits the job.

What does that mean in terms of wiring the 12V batteries to the inverter?

from the formula above:

current = power divided by voltage

In our example, we have an 800W inverter that runs on 12V

The current would thererfore be:

current = power divided by voltage
current = 800 watts divided by 12V
current = 66 amps.

That is important info because you can not use light gauge wire to carry 66 amps worth of 12V to the inverter nor could you use a 20A fuse to protect your inverter.

Now that's a lot of science for a guy who just wants to run a toaster on an inverter right?

800W / 120V = 6.66 amps

Using garryp's ratio 11:1, 6.66 x 11 = 73 amps.

That is a good ratio with a good safety margin.

This is all just MHO and should not taken as solid technical advise. In other words, don't blame me if you blow yourself up.