Power Inverter

I"m interested in getting a power inverter that hooks to a 12V dc power supply and outputs 120V ac. Not sure how to determine size needed. I know that depends on what I plan to use it for but still have ?? For instance, my wife's blow dryer is 1500 watt. Does that mean I would need at least a 1500W inverter just to run her blow dryer? If so, I can't imagine it running an angle grinder or etc. Do any of you have FIRST HAND experience with an inverter like this? What suggestions do you have? Thx

Im not sure why or what it means but I know you want a pure sine inverter

1500 would be the bare minimun for the hair dryer but if you run an inverter at max you cut there life short, 2000W would be better for this.
On your angle grinder multiply volts (120) times amp to get the watts needed.

A hair dryer would operate on a crude square wave inverter ,
Let along a modified sine wave inverter . No need for a $$$ pure sine wave inverter .
Inverter maybe rated for 1500W . That could be an intermittent rating and not continuous .
The hairdryer will draw approx 140amps from the battery.

My cheapest 4 1/2 grinder will run on my 400 watt inverter, as long as you don't push on it, and have the truck running.

Inverters get talked about a lot on Recreation Vehicle web sites. RV.Net

Tracy, YES Ive (49 year RV owner and several battery solar and inverter etc. installations) had years of "FIRST HAND" experience with many different brands types and sizes of Inverters and yours is a good question, so here are my "opinions" (Im sure others will follow, any electrical question gets a ton of responses, take your pick lol)...


1) First of all you mentioned using a 12 VDC "Power Supply" Obviously you don't have anymore capacity then the "Power Supply" does. Is that a battery or what??? Energy stored in batteries are the typical source of power to run an Inverter but again there's only X finite amount of Amp Hours of available energy before an Inverter would shut down. The "Power Supply" be it batteries or whatever ?? also has to have the ability to deliver X amount of continuous Amps to the Inverter Input sufficient to run the 120 VAC attached load.. See NOTE below if its an engine battery and the engine is running the Alternator can be pumping amps into the battery at the same time to make up for Inverter use !!!

NOTE depending on the Inverters efficiency typically for every amp at 120 VAC Inverter Output it will draw somewhere around 11 or so Amps out of the battery or Power Supply that's serving it. A 1500 Watt blow dryer that takes 12.5 amps will draw somewhere around 137 Amps out of your battery or Power Supply

2) An Inverter may have a "Continuous Rating" (say for example 1500 Watts) plus perhaps a "Surge Rating" (Higher, maybe 2000 or more watts) available for short term energy bursts above the Continuous rating.

3) To power up a 1500 Watt blow dryer, the absolute MINIMUM Inverter "Continuous" capacity would be 1500 Watts HOWEVER thats cutting it awfully close and Id prefer a 2000 Watt Inverter to be on the safe side

4) For many non sensitive applications (like a blow dryer) a much cheaper Modified Sine Wave (MSW) Inverter will suffice. However there are "some" electrical devices and appliances that fare much better if they are fed with a Pure Sine wave (PSW) Inverter. If you're unsure of all the devices the Inverter will be used to power up and to allow for expansion and to be on the safe side I would go ahead and bite the bullet and invest in a PSW Inverter lest you try a MSW and end up damaging something then have to purchase a new appliance !!!

SURE a cheaper MSW can get you by like to power a resistance heating appliance like a blow dryer

5) You speak of an angle grinder NOTE such a device may actually require LESS power then a 1500 watt blow dryer. See what its rating is, you may be surprised, it may be less then 1500 watts ??

6) NOTE Devices like a motor is where an Inverters Surge rating comes into play and may be needed. Thats because a motor may require 3 to 6 times as much initial surge current then its running current. For example if it takes 1500 Watts to power a motor device, if the Inverter has say 2000+ Surge Capacity such may be needed and will suffice to get the motor started.

7) Its good if the Inverter is close to your "Power Supply" such that voltage drop in the input (from 12 Volt) cables can be minimized. Be sure to use adequate rated Input cables.

8) One can find a lot of 12 VDC tools and appliances and if used direct off 12 volt batteries that saves the Inverter heat losses MUCH MORE EFFICIENT OPERATION versus an Inverter

Soooooooooo the absolute MINIMUM Inverter to power a 1500 Watt blow dryer is 1500 Watts Continuous and an angle grinder may require more or less I cant say from here, but Id recommend at least a 2000 Watt and Id consider going ahead paying more to get a PSW in case you ever need to power up some sensitive tool or appliance or electronics that requires PSW Inverter. Sure a cheaper MSW will work for many tools appliances and a quality 1500 Continuous Watt (if Surge rating is adequate) "might" work for a 1500 Watt blow dryer ITS YOUR MONEY AND YOUR CHOICE

What puzzles me more is if you understand and have adequate "Power Supply" (batteries ???) to run an Inverter ??? A wimpy 12 Volt 100 Amp Hour battery pumping out 137 Amps into an Inverter to power a 1500 Watt blow dryer is only going to work for X time you know !!!!!!!!!!

NOTE if youre using lead acid batteries it best if they are 1) full true Deep Cycle and 2) Its best not to discharge them over 50% of their rating...

NOTE if youre using say your pickup or automotive battery to power up an Inverter if the engine is running the Alternator can be supplying charge into the battery to make up for what the Inverter is drawing.

FWIW My 2000 Watt Continuous PSW Inverter can run my (One at a time) microwave, coffee maker, toaster, wifes 1500 Watt blow dryer, all sorts of electronics like TV and laptop and chargers and DISH receiver etc etc NO PROBLEM yayyyyyyyy


There ya go, that's ONLY my "opinion" and I'm sure others may have a different "opinion" and hopefully can add to this as Im sure I MISSED SOMETHING grrrrr

Best wishes God Bless hope this helps, post back any questions and insure your "Power Supply" batteries have the capacity to power up the Inverter for the needed time

God Bless America

John T

I had a cheap inverter from K-mart. It said right in the directions it would NOT run a resistive load. I wanted it to run a simple soldering iron and it would not run it.

Well that's just great, John!! lol So now I have to look at my inverters to see if they are msw or psw assuming they even say on the tag. I have a 2000 watter in my PU that has never been used. Have to try it but don't know what type it is.

Will a laptop work off a MSW inverter? Wouldn't want to mess one of those up.

You also have me wondering about using my little inverter welder plugged into an inverter. A double inversion or a reverse inversion? Thanks.

You're sure welcome, glad to be of help, and of course people are free to do as they please, that's what I do lol

Best wishes and God Bless

John T

To give you a general idea I have a cheap 750 watt inverter.

On my dump truck it has no problem running a sawzall and angle grinder but that is with 3 big batteries, plenty of juice.

Running the saw off the inverter on a pick up truck you better keep the engine running or you will be boosting it.

Another cheap 400 watt one works great to run a Dremel tool for sharpening chain saws, trouble light, phone + computer charger etc.

You say "Running the saw off the inverter on a pick up truck you better keep the engine running"

That could well be darn good advice depending on the saws power, how long it runs and your alternators capacity, you don't
want to drain the battery so bad you cant start the truck grrrrrrrrrr lol

Best wishes

John T

We run/charge our lap-top computers with a cheep plug-in inverter in our motor home, while on the road.

Dusty

Thank you all for your replies. I'm thinking a 3000W minimum hooked to my truck or loader battery for running 1 power tool at a time for a limited time (sawzall, angle grinder, skill saw, etc).

most computers have switching power supplies that take the ac voltage in, and convert it, so they usually will run on a msw inverter as long as it has the correct capacity. Older equipment may be more sensitive to the modified sine wave, or in some cases more of a square wave...

A 3000 Continuous watt Inverter, and especially with the truck running and its alternator pumping charging current INTO the battery, should well suffice for X time (subject to load and battery and inverter and alternator) for many tools. Congrats for choosing a possibly larger then needed unit to allow for safety and expansion. USE big enough properly protected cables from battery to Inverter input.

John T

John T
Isn't 137 Amps close to starter current?

Aren't deep cycle batteries designed more for smaller currents and a longer time?

I don't think too many batteries will last very drawing 137 theoretical amps. Account for the efficiency of inverter the current drain is north of 137.

For about the cost of a bank of batteries and invert I'd be looking at a Champion RV (Honda clone)generator.
George

I have run 2 different laptops for many
years off of modified some wave inverters.
Laptops have inverters that don't care
about the wave type. I don't know about
desktop computers. My 19 inch led tv works
fine too, but I have done away with the tv
inverter and run it straight from 12 V. A
large inverter will waste more power than a
small one. I have three different sizes.
140, 400 and a 2000 watt. The 400 watt
inverter will run my 3/8 drill motor and my
4.5 inch grinder. The grinder takes quite a
few watts, so I only use it when the sun is
on my solar panels to save my batteries. My
refrigerator runs good also on my inverter,
but I only use it in the summer time. I
just have an icebox and bring ing ice every
morning. If the temperature is cold enough
to freeze a bottle of water solid; when it
thaws, I have distilled water too!

I just remembered. I did run a desktop computer off of my inverter but it was many years ago. Your results may vary on that though. No guarantee!

Most modern electronics use switching power supplies, so don't care if it is pure sine wave or modified sine wave, as long as the voltage is reasonably close to equipment rating (lets say 110 to 125v would be good). For your hair dryer application, 2KW continuous would work ok.
You WILL need a big Fooken Battery for the load; as some have indicated, 130-150 DC amps is not unheard of. You will need a way to maintain that draw while using your inverter. I used to use a 2KW inverter on my service van, running a light-duty MIG welder, on very low current settings, satisfactorily. Of course, I had to keep the truck running all the time. My 2KW happen to come from the H..Fright store, and has held up well, but stuff from them is hit or miss.
You will also need 2/0 cables for that current, with crimped-on connectors; battery clamps won't work well, due to the current. The closer to the battery the better; copper gets expensive, and a 12 gauge extension cord is a lot cheaper than 20 feet of 2/0 welding cable. zuhnc

(quoted from post at 20:29:52 02/20/21) Thank you all for your replies. I'm thinking a 3000W minimum hooked to my truck or loader battery for running 1 power tool at a time for a limited time (sawzall, angle grinder, skill saw, etc).

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Get as big as you can afford. I had an 1100w in my work van to run a printer. They changed it out for a bigger one and I got the old one. The printer only drew about 6 amps max at 120v which is about 720 watts if I remember the formula right. Depending on the temp, the printer would kill the inverter regularly. I've tried running a 3/8" drill off it, it might stand it once out of 10 tries with the overload kicking in 9 times. It will run an old B+D 1/4" drill usually. A sawzall or skilsaw is out of the question.

I'd go big if I really wanted to use it. Or, as an alternative, you can get an alternator that produces 120v power and install it in your vehicle with some extra belting and mounts if there's room. My dad had one in his old F100, but those had a lot more room in the engine bay.

Years ago a friend's son had a 400 W, 120v that he wanted me to install on his truck. I read the directions and installed it. When time to test it came, to get full voltage the engine had to be running wide open.......economy of scale????? I told him that he had a very poor investment and basically a bad idea.

(quoted from post at 07:57:35 02/23/21) Years ago a friend's son had a 400 W, 120v that he wanted me to install on his truck. I read the directions and installed it. When time to test it came, to get full voltage the engine had to be running wide open.......economy of scale????? I told him that he had a very poor investment and basically a bad idea.

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After reading what you said in your post about needing the engine running wide open I wonder if what you installed was one of those GTO power converters?

An inverter does not require an increase of alternator output to function.

I had one of those GTO converters on a truck years ago, the output was 120 volt DC and yes the engine rpm needed to be up to get that voltage.

I had a swing crane I had made on the back of the truck, it had a surplus 120 volt DC motor hooked to a gearbox that turned a winch drum.

At idle when you hit the switch it would not do anything, hop in the truck and hit the gas pedal and it would lift just fine.

Swing the load over the bed of the truck, hit the reversing switch, touch the gas and use the pedal as a speed control to lower the load down.

Texasmark, I don't think that was an inverter. There were aftermarket voltage regulators that used the vehicle alternator to produce 120v, and there were belt driven and DC motor driven generators to get 120V before the days of inverters.

I don't know what it was electrically. An inverter alternatively inverts current producing AC being driven from a DC source....whatever mechanism it takes to do that. I know back in the days of 120V tube radios in autos, a plug in "vibrator" sufficed in obtaining that objective. Today it's step-up transformers and solid state switching circuits.