Power Inverters

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I searched the forum and didnt find much on this subject so am curious to know if anyone uses/has used a power inverter instead of a generator during a power outage etc.

This is a review of a 2000watt continuous power inverter... from HF $170

" turned on my a/c 6,000 btu unit,Internet router and my big 54 samsung tv in that pass huracan Matthew... I just let my car run and put the cables straight to the battery... work 100%"

another review

"Had an ice storm and needed power. Hooked the inverter up to my diesel truck. I was able to run the furncae, refrigerator, freezer and some lights all at the same time until the power was restored. Handled the loads easily"


I have a gasoline generator and was thinking about upgrading it..but for $150 with a coupon this seems like a viable option for a backup generator.

As a rule i dont like anything harbor freight with wires involved...so am interested to know if there are 'better options'
 
Sorry, I just do not believe these reviews. The truck alternator is creating 12v power which has to converted to 120v. This is a very wasteful process. In addition you would have to find a way to hold down the gas pedal so the engine runs at 1800 RPM.
You might be able to do this for about an hour but after that I think you could damage the truck.

truck power
http://www.ar15.com/archive/topic.html?b=10&f=18&t=649614
 
Let's do the maths shall we?
2000W @ 110V is 18.8A.
2000W @ 12V is 166.6A.

Now these inverters are usually somewhere in the order of 85% efficient on a good day. Expensive ones are better. So, we have about 2353W real electrical load at power factor 1. Let's be generous and calculate on that. So we have a 12V load of 196A.

I dunno about your car, but the alternator on mine is rated at 80A at a couple of thousand RPM. The parasitic load in my car at that RPM is about 15A, so that leaves 65A of available capacity, meaning if I sat in the driveway with my car "idling" at 2500RPM I'd be able to sustain about 780W into an inverter.

Now, if it were a Prius (which is basically an optimized generator on wheels) then we're in a whole different ballpark, but simple maths allows me to confidently call [censored] on the reviews.
 
Excluding losses due to heat converting 12v DC to 120v AC

2000 watts = 2000/14V = 143 Amps

This is not a sustainable option if you lose power for more than a couple hours. Vehicle alternators are not designed to output their max amps at 100 percent duty cycle with the inadequate cooling created by engine idle speeds and stagnant under hood airflow.

for an emergency it works, but your alternator will take a beating.
 
Originally Posted By: Brad_C
Let's do the maths shall we?
2000W @ 110V is 18.8A.
2000W @ 12V is 166.6A.

Now these inverters are usually somewhere in the order of 85% efficient on a good day. Expensive ones are better. So, we have about 2353W real electrical load at power factor 1. Let's be generous and calculate on that. So we have a 12V load of 196A.

I dunno about your car, but the alternator on mine is rated at 80A at a couple of thousand RPM. The parasitic load in my car at that RPM is about 15A, so that leaves 65A of available capacity, meaning if I sat in the driveway with my car "idling" at 2500RPM I'd be able to sustain about 780W into an inverter.

Now, if it were a Prius (which is basically an optimized generator on wheels) then we're in a whole different ballpark, but simple maths allows me to confidently call [censored] on the reviews.
+1 You'll have difficulty with a well pump with this lash up.
 
I don't buy it either. The first claim involves about 1900 watts of power consumed, which is about 135 amperes at 14 volts at the vehicle's battery. In reality, it's way more than that after you factor in efficiency losses and all that. The second claim is even more dubious since two very inductive loads are involved. Inductive loads draw more power at startup, even as much as 600% more than the average running draw once the compressor is up to speed. Using your car for this purpose is a recipe for disaster.

In fact, this is a weakness of gas powered electronic generators. The initial current draw is way more than what a marginally sized unit could deliver. You'd be better off with a real electromechanical genset.
 
I have thought about getting one of those to put in my camper permanently instead of using the 750W one I have now - it runs the fridge and a fan just fine.

I had no issues running the 750W at idle on the jeep. It has an actual throttle so I considered putting a broken SD card or something in the throtle arm just to bump the idle up a bit. But I'll just install a factory high idle switch.

Ultimately a generator is probably a better option, but this is way more convenient to use with a vehicle.
 
I got a question on this that bugs me as well........I have a 6500W gas gen that's 7500W peak. I know it's "dirty" power. What can I do, while keeping this genset, to have 6500W of clean power. Anything?....something tells me there isn't.
 
When I looked into this a while ago (years ago?) it seemed wiser to get a gas generator and not a gas powered invertor for running a well pump or furnace. Peak/surge load at startup favors those more primitive machines. Even though the invertor is more efficient on gas (since it can lower engine rpm and not run at a fixed high rpm all the time), for the time it is needed, it's not so bad.

I've yet to figure out the "dirty" power issue. Fridges and motors might not like wrong frequency, and brownouts even less; but most electronics just run into a rectifier bridge and are rated to run on 90Vac to 240Vac. Stuff that is "only" 110 and using a transformer won't like a gas invertor I'd suspect, not unless if it had a nice modified sinewave output. Anyhow, there are power line filters out there; how effective they are, I dunno.

Car powered invertors are kinda cool, but as pointed out, pretty unrealistic for the power needed. I do know of someone who, during a power outage, ran a cord out to his Prius for the duration. But he was using it to run some lights and nothing else.
 
The only way I would consider that is if I had a small solar installation, a battery bank, and a solar charge power controller, and a pure sine wave inverter. I certainly wouldn't try it off a car battery and alternator. As others have pointed out, the current draw at 12 volts is huge- you basically need welding cables to feed a true 2000-watt capable inverter, and your battery bank won't last long at full load.

What I haven't seen mentioned is the need for a pure-sine inverter. Most inexpensive inverters are modified sine wave inverters, which means that they basically put out a sawtooth shaped voltage wave on the 120v AC side. Light bulbs don't mind that at all, but electronics and motors don't respond well or predictably. Motors will be noisy and run hotter than normal, electronics may just fail after a short time. Pure-sine inverters are also more efficient, but they cost more up front.
 
Originally Posted By: berniedd
I don't buy it either. The first claim involves about 1900 watts of power consumed, which is about 135 amperes at 14 volts at the vehicle's battery. In reality, it's way more than that after you factor in efficiency losses and all that. The second claim is even more dubious since two very inductive loads are involved. Inductive loads draw more power at startup, even as much as 600% more than the average running draw once the compressor is up to speed. Using your car for this purpose is a recipe for disaster.

In fact, this is a weakness of gas powered electronic generators. The initial current draw is way more than what a marginally sized unit could deliver. You'd be better off with a real electromechanical genset.

That inverter probably has a large capacitor of some sort though and maybe able output quite a high amperage for a short time. I had a small 300W inverter in the car to run a cordless drill battery charger, and with it plugged into the cigarette lighter the radio would stay on for about 10 seconds after I shut the car off. The capacitor in the inverter must've been back feeding power to the car through the lighter.
I agree though that you can't draw large wattage out of a cars 12V system for very long.
 
The beauty of Electricity is it is sooooo simple ... it's all math, and it's even easy math, with one three part equation answering all your questions ... enter two values, the third is easily discovered.

As many have already posted, the reviews claiming other-worldly results are seeded (made up by someone associated with the seller, pretending to be a buyer). Either the math is right, or these devices are actually magic. You decide.

We don't even have to go to the wear on your alternator, which I guarantee won't last under full load for very long. Add the cost of a new one to your "bargain".

Nor do we have to consider power factor, which is a big deal with a generator powering things the Utility normally takes care of, because unless you are a commercial 3-phase user, there is no way to account for Power Factor in a home service, so they cannot bill you for it, and you get the extra power they must generate for free (sort of ... they raise the rates to compensate).

Finally the quality of the power isn't accounted for. You can get a proper 60 Hz 120V Sine Wave from a non-grid power source, but it's expensive. Normally that would not matter; the generators or converters would also be expensive, and that would be that. But there is a cheaper technology that can be used, so it does become an issue. Again, if you power your devices and appliances with dirty sine waves, they will not last as long, so you have to figure the cost of early replacement of the stuff in your home you drive with the source.

Now the good news. All the hard stuff mentioned above is irrelevant, because these things simply cannot work as advertised.
 
I have a chrysler alternator rated at 120 amps and 50 at idle, and a digital ammeter on my dash indicating these ratings are mostly accurate.

I also have a Thermocouple on my alternator casing.

At hot idle, maxed out at ~ 50 amps, the temperature rises quickly to the 200F range, and then max amps drop to the low 40s and if I don't turn off loads, system voltage starts dropping.

At highway speeds at 50 amps output it will be about 106f. Even low speeds and low rpms and high loads on alternator will have its temp climb rapidly. Ideal is highway driving at 2000+ rpm

If there is an inverter on the battery, and the alternator cannot meet the electrical demand of it, it comes from the engine battery, which is not designed to be deeply cycled, and will fail prematurely because of it.

Also the quality of the modified sine wave can vary in the amount of steps.

Pure_Sine_Wave_vs_Modified_Sine_Wave.jpg


Harbor fright inverters are basically square wave, and have a horrid reputation on RV forums and every purchaser regrets their decision, wishing they saved their money and put it toward a better product.

The reviews prove only that reviews cannot be trusted.

'85% efficient' is also likely a best case scenario, never realized.
 
get an extra battery with a 12v solar cell (or a couple of them) to keep it topped up. Run an inverter off that if you get regular power outages.
 
An inverter connected to the car should be a relatively low powered unit for intermittent or low power devices. Examples are: charging your phones, running your fridge (only a few times during the day), powering your TV, etc. Using a high power inverter to run an AC unit or furnace is asking for trouble; a car alternator cannot keep up and the load would quickly deplete and possibly damage the battery.

I will be soon building a home battery bank for brief outages when I do not want to pull out the generator. I can keep my sump pump connected to this for peace of mind overnight.

This guy http://www.steven1234.com/ has tons of information on all of this.
 
My father in law uses some older 3000 watt inverter by plugging it directly into his Ford F-150 battery and leaves it idling away.

It is able to power fridge tv, cable and his boiler for New England coastal storms and he lives ocean front.

With regards to vehicle not lasting idling away he has done this over multiple times for 5hr to 3 days and truck has 300k+.

Is a generator better, likely yes however this setup is elegantly simple and requires no maintenance.....
 
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