power inverters

any of you guys have/use a power inverter? (i mean like, 1500 watts, 2000 watts, etc., for construction equipment, circular saws, etc.?)

b.w.

Reply to
William Wixon
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Yes. I have used and designed inverter systems from small power plug in units (~200W) to large multi unit 10,000W systems in yachts using large numbers of lift truck batteries. Why?

Stephen N.

William Wix> any of you guys have/use a power inverter? (i mean like, 1500 watts, 2000

Reply to
Stephen N.

I have a 750 W continuos rated inverter and this is plenty for most things.

A 1500 W inverter is going to really put a huge load on your battery. You will need close to 150 A from your battery to maintain the rated output of the inverter. Usually not a good thing to be doing if you are doing this with only one battery.

Reply to
Mark Jones

Why would anyone try and run an inverter without the engine running? I ran a 300 watt for light duty items when I drove truck for a living, things like my laptop computer, small 13 inch TV. For larger items like the microwave a 1500 watt. Most devices pull 30-45% more wattage in start up then what it takes to run, the invertors has to be large enough to handle the start up draw. Wire any inverter over 450 watts to the battery. Given how the price of small gensets has dropped, I would save wear and tear on truck engine and get a genset.

Whitelightning

Reply to
Whitelightning

Sorry... a 1500 watt inverter would probably draw LESS current off the battery under a 750 watt brush-motor load (most construction tools use brush motors). That 1500 watt inverter *is* going to draw 150 (approximate) amps but only on motor startup or if stalled. The rest of the time; its going to draw about 10 times (in amps)the load (in 120VAC watts). Motors draw power in almost direct relationship to the mechanical load on them.

My Skil 77 draws 11 amps starting surge. "Just running" is about 1/2 amp; mostly just to make noise. Usual 2X4 cutting draws 3-6 amps. Running right at stalling draws 9-10 amps. Remember these are at 120VAC.

Reply to
nobody <"" spam.info

On Sun, 02 Apr 2006 07:19:02 +0000, nobody rearranged some electrons to form:

He said "to maintain the rated output of the inverter". Those inverters are probably no more than 70% efficient, which means to get 1500W out, you have to put nearly

2000 W into it.
Reply to
David M

Try reading what I wrote again. What I wrote is correct.

Reply to
Mark Jones

Try about 85 to 95 percent efficent and they are most efficent at full load and least efficent at lighter loads. A 1500 wat inverter may use

6 to 10 amps just idling where as a smaller one will use a lot less power idling or at light loads. If you expect have a 150 to 200 watt load all the time, use a 300 watt inverter or so as you will get better battery life than with a 700 or 1000 watt inverter with same load.

----------------- The SnoMan

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Reply to
SnoMan

On Sun, 02 Apr 2006 15:11:41 +0000, SnoMan rearranged some electrons to form:

Not all DC-AC converters are more efficient at higher load. It all depends on the design. A simple square-wave output is only as efficient as the switching elements and the magnetic components. Some pretty good power FETs with low Rds can cut your losses, but as with everything else, better components+better engineering = more $$. If you try to smooth a square-wave output into a pseudo sine wave, the efficiency goes down. A true sine-wave output converter can be efficient but will cost more. Again, you get what you pay for.

Reply to
David M

You are talking to a guy with a 30 plus year engineering background. The inefficency you speak of from wave difference will result in reduced efficency in the device attached to it, not the inverters efficeincy. THe shape of the wave was a lot more critical to attached devices when transformer based supply were used in device but now that they are pretty much all swithing power supply (except of a induction compressor motor or the like) wave output is not much of a factor. If the efficency was a low as you suggest, there would be a lot of inverter burning up, especailly smaller ones for heat disapation. I have a 300 watt unit that barely gets warm to the touch with a entended 150 watt load on it.

----------------- The SnoMan

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Reply to
SnoMan

Warning, Dave!

Snoman walks like a duck, looks like a duck, and quacks like a duck, but you'll never get him to admit that he's a duck!

lol

Spdloader

Reply to
Spdloader

Sno, you are talking to a guy with a 25+ year engineering background, starting with an EE degree...

Reply to
Matt Macchiarolo

On Sun, 02 Apr 2006 18:50:43 -0400, Matt Macchiarolo rearranged some electrons to form:

One of our most recent projects was a high efficiency DC-DC converter. Push-pull output with custom magnetics. Efficiency above 90%.

And a VERY recent project involves interaction between a ferroresonant transformer and a active-power-factor-correction UPS. Seems that the UPS front end smoked... some kind of resonance with the ferro, perhaps? That one isn't over yet.

Reply to
David M

On Sun, 02 Apr 2006 21:39:21 +0000, SnoMan rearranged some electrons to form:

Not quite. Obtaining a sine wave from a square wave removes some of the energy in the output (think Fourier series, low pass filter). That energy has come from somewhere... it's dissipated as heat in the inverter. The so-called "modified sinewave" inverters are simply push-pull outputs, through some magnetics (transformer). A lot of the high frequency harmonics get filtered (but not all!) and that energy is dissipated within the inverter.

On the contrary. Switching power supplies, especially cheap ones, can display a very low power factor to a source. The output of the source can easily become overtaxed if the current required is significantly out of phase with the voltage (the cause of a low power factor).

If

Hmmm... better check your math. 150 W out even at 70% efficiency = 195W input. Not even close to the maximum rating. 80-90% is probably more likely, however, so it's even farther away. At 80% efficiency, you're dissipating 37 W. A good heatsink or metal case would conduct that away pretty well.

Any inverter will burn up if you overload it, so I guess I don't understand what you're saying.

Reply to
David M

On Sun, 02 Apr 2006 22:17:48 +0000, Spdloader rearranged some electrons to form:

I ain't skeered.

I'm sure my 25 yrs in electrical and electronics engineering will measure up to his 30 years of snowplow driving.

Reply to
David M

Agreed, but he's convinced that he's the AUTHORITY on any thread he chooses to enter.

When I said duck, I meant idiot.

More power to ya brother.

Later Dave,

Spdloader

Reply to
Spdloader

i am curious about inverters. i don't know a damn thing about them. seems like it would be handy to have one hooked up to my truck, added up the cost of a few components ($421 3000 watt inverter, $358 two optima batteries $159 isolator switch) seems like $939 might be too much for a "just in case" device. i wondered how many people have/use them and how they feel about them. worried about burning out my alternator. ascertained the alternator is 115 amps. if in put in an inverter i was assuming i was going to put in two deep cycle batteries. was thinking about/wondering if it was possible to install the batteries in the space between the outer body skin and the sheet metal of the cargo bed, on the passenger side, build a weather proof enclosure for them. i'm only just in the "wonder if it's possible" stage of this thing.

thanks for y'all's input. (didn't mean to initiate a argument.)

b.w.

Reply to
William Wixon

I would've guessed train-driving, but that's good, too.

Reply to
Matt Macchiarolo

You could do this and it is pretty straight forward. It is similar to the type of system you'd use in a small RV application. You haven't listed the cost of setting up the battery storage area or any of the wiring components.

Your alternator will be working pretty hard to charge the extra batteries and very hard while you are using the inverter so you can expect early alternator failure. You would likely need to get a heavier duty alternator which may be difficult to find and it won't be as cheap as the stock one.

Remember the equation P=IV that is Power=Current x Voltage. That means that 3000 watts at 12 volts would require a current of 250 amps. That is a pretty hefty current to haul out of the system even with two deep cycle batteries. Remember also that no inverter is 100% efficient, more likely ~85% if your lucky meaning even higher currents for a given power output.

Battery capacities are measured at a certain discharge rate, i.e. C/10 or one tenth of the capacity per hour for ten hours. The higher the discharge rate, the lower the actual amount of power you get from the battery. A 50ampHour battery may discharge at 5 amps for ten hours but only three hours at 10 amps and fifteen minutes at 50 amps.

Of course you probably won't use your inverter at full power constantly but it something to keep in mind if you decide to plug a kettle into the system and the engine is not running.

I am presently using a 3000 watt inverter in a 24 volt semi-submersible vehicle electrical system and it runs constantly at about half capacity or more for 12 or more hours at a time. The inverter has many hundreds of hours on it and we have not had a single problem from it. We do have to replace the batteries fairly often though but we use them far more heavily than you are likely to. The inverters are only part of the total draw.

In short, yes it is easily possible but it is fairly expensive. As for ease of use once you set it up, it is the cat's meow!

Stephen N.

Reply to
Stephen N.

Since the beginning of time, the formula is P=IE. E is the letter used to designate Voltage.

Reply to
Junior

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