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Originally Posted by Uturn2001
Basic inverter lesson.
Most all have a dual wattage. The lower number is how many watts it will put out continuously, the larger number is how much it will put out in a short burst, usually 5-10 seconds.
To run any appliance you will need an inverter at least equal to, in continuous output, the watts required by that item. Some items like small fridges require a lot higher of a wattage output because of the energy required to start the compressor.
If the item you are looking at does not have the wattage listed simply take the amps it needs and multiply it by the Volts it takes. For example a 20 amp 110 volt item will require at least a 2200 watt inverter.
Most 13 inch TV's and TV/Dvd combos will run off a 350/400 watt inverter. The larger the TV the more power it will take.
400 watt inverters are pretty much the largest you can get that will plug in. Once in a while you can find a 500 or 600 one, but most 12v power outlets are not wired to handle that much power and will either not provide enough juice to power the inverter or it could cause an electrical fire due to overheating of the wires assuming your fuse lasts long enough.
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Great post Uturn. Especally the continous vs. peak part. Usually the inverter just burns up and fails when the user buys the peak rating for a continous device ...
Just to follow up on this ...
The problem is not starting with amps .. but starting with power. A TV uses about 20 watts. A Microwave 550 on the low end .. 1200 on the high end.
The voltage is fixed at 120 AC in the US.
So how many amps are required to power the item?
Ohms law ... volts X amps == watts (or power) You can reverse the formula to find the amps. In Uturn's example the high powered device uses 20 amps in a household environment . that same device will use 188 amps in a 12 volt DC environment. :shock: That is in the spot welder range ... :twisted:
The basic engineering problem is that amps lose heat. It is one thing to power a 2250 WATT device in your home .. it is quite another to power the same device in your truck. Thus the problem companies have with inverters. You can set your truck on fire! :shock:
Just a note ... The problem the engineer has in developing devices is that higher voltage and lower amperage is the most effiecent. However .. higer voltage means that the electricity can jump and arc to things .. including the user, and this would be bad. Lower voltages means heat and things catch fire .. this is bad too. Your laptop might be an example .. this is a case of low volts and high wattage producing heat ... Thus the US settled on 120 volts AC .. the highest voltage that was determined to be safe in the household and should not arc to the user .... :P
The truck has lead acid batteries and each cell produces 2.0 volts. 6 cells == 12 volts. Two batteries in serial produce 24 volts .. enough to turn the starter.
Thus this is how you are stuck with a 12 volt system but needing to power things requiring 100's of amps in this environment.
Now that we understand power .... that 2250 watt device and inverter at 12 volts needs 188 amps. The wires to safely carry this current are as thick as ropes. Installing regular 20 gauge wires will mean that the wires will look like light bulb filliments .. that is until the truck burns up or the wires burn like fuses. It also means not only do we ned ropes that might not fit through pre-drilled holes but also that the installation must be professional with rubber grouments protecting the wires from chaffing.
So many companies frown on inverters.
Another problem .. if you have a refridgerator .. microwave, ,,, hair dryer etc running .. you are going to have to high idle the truck. DO NOT start a high wattage device without the truck running. It will drain the battery and damage the system.
Reason #2 companies frown on inverters.
Third problem .. most inverters do not produce a sine wave but a modified sine wave. That could be hard on certain devices like motors. I purchased a less expensive full sine wave inverter. That cheap Cobra inverter at the Pilot does not produce a full sine wave ... and probably will not last. The other advantage of a better inverter is being able to be a converter and enable you to plug into 120 volts AC and charge the batteries.
Good luck ...
BTW) Watkins Sheppard will install a 1500 watt continous inverter you purchase .. for you.
inverters, TV's, microwaves etc etc......
