1500 Watt inverter load on the alternator?

I live in a condo in California. I have emergency survival basics stored that will allow us to cope with no food, water, power, shelter for a few days.

I don't have a generator. And I don't want one. They are big. I have no place to store it. I don't want to store gasoline for it. And when they run, they are noisy.

I'm prepared to survive without power for a week. But, it would be nice to be able to get some power to ease things. So I was thinking about getting an inverter.

My carport is steps away from my condo, and I even if the carport fell down in a large quake I could clear it away.

The idea is that I could bolt a 1500 watt inverter to the battery posts of my Passat. Then run the car for 2 to 3 hours a day to power the fridge and top up batteries. This assumes that I can run an extension cord to the fridge, and that I can get to it. More than likely I will be able to.

I figure that letting it run 2-3 hours a day, and not opening the fridge door very often, will allow us to preserve food longer. Make life a little easier.

The inverter is small so I could store it in the emergency box. It can put out 1500 watts, which is more than enough to handle the spike when the compressor turns on. And I think my fridge can handle a modified sine AC, versus the pure sine it normally gets from the power company. Worse case I burn out the fridge motor prematurely. Least of my worries in a disaster of that scale.
http://www.theinverterstore.com/2000-watt-power-inverter.html

Here is the problem, or worry. Can the alternator handle it? The car battery should be able to absorb the spikes from the compressor motor. But if VW only made the alternator strong enough to run the motor, lights, stereo, and keep the battery topped up, then can it handle the additional load of up to 12.5 amps drawing on it?

It would really suck in my mind to have this nice life-safer for the condo, then when I need to use the car after the disaster, it won't run because I've fried the alternator.

Thoughts?

Thank you

Yankinwaoz said:

Here is the problem, or worry. Can the alternator handle it? The car battery should be able to absorb the spikes from the compressor motor. But if VW only made the alternator strong enough to run the motor, lights, stereo, and keep the battery topped up, then can it handle the additional load of up to 12.5 amps drawing on it?

Click to expand...

12.5 amps at 12 volts is 150 watts. 1500 watts would be 125 amps. This also assumes your inverter is 100% efficient (which is impossible). In other words - If you are drawing the full 1500 watt output of the inverter, it would require over 125 Amps input at 12 volts. However, the load you are talking about will not be the full 1500 watts (at least most of the time). Your car's alternator/battery probably could handle it for a while, but there may be better ways to supply backup power. Remember that your starter plus your glowplugs together probably draw more than 125 amps every time you start your car.

Have Fun!

Don

JSWTDI09 said:

12.5 amps at 12 volts is 150 watts. 1500 watts would be 125 amps. This also assumes your inverted is 100% efficient (which is impossible). In other words - If you are drawing the full 1500 watt output of the inverter, it would require over 125 Amps input at 12 volts. However, the load you are talking about will not be the full 1500 watts (at least most of the time). Your car's alternator/battery probably could handle it for a while, but there may be better ways to supply backup power. Remember that your starter plus your glowplugs together probably draw more than 125 amps every time you start your car.

Have Fun!

Don

Click to expand...

Yes.. sorry. I screwed up a decimal place. 150 amps in theory. But perhaps 120 amps realistically.

My question would not be how much current will my alternator put out (which is kinda what you are asking). My biggest question is how much current does your alternator put out with the engine at idle. I do not believe that your car will raise the idle speed to meet the needs of your inverter, so this may really be your limiting factor (unless you want to sit in the car with your foot on the go pedal while your fridge runs).

Have Fun!

Don

I've used a 1200W (I think.. can check later) inverter off my Golf during a few one-day power cuts. The car seemed perfectly happy. Fridge/freezer was no problem, the jet pump that pressurizes the house water supply was a bit more trouble - if I remember correctly, it would trip out the inverter if the pump started when the inverter was running but if the inverter was switched on with the pump already connected the inverter's soft-start allowed it to get going and the pump would then run OK.

Addressing the OP, I agree with "JSWTDI09." The issue here doesn't lie with the inverter, but the specs on the Passat's alternator. How much power, and for how long, will it put out at various RPMs? There may (or may not) be a simple graph somewhere detailing the instantaneous output of the alternator, but the output over time that the car's system is capable of (the time being your 2-3 hours, say) is quite another matter.
Backup generators all have their pluses and minuses. We had to go through this six years ago for our house, and since we have a 1K gallon propane tank serving the house, decided on a 10KW standby generator using that fuel source, so none of the issues relating to gas or diesel apply. Yes, we had to spend some money on this, but the backup generator is designed to do what it does, and could be sized to fit our needs. A car's alternator / battery system may or may not be able to handle the continuous output over time that your backup generator needs require.
I am speculating at this point, but heavy loads on a car's system are intermittent, and don't last for very long, so I'm not optimistic about this kind of setup. The most extreme load a car's system faces, as has been mentioned, is at startup, and that's never for very long, usually just a few seconds.

None of the above is incorrect, but unless I missed something we never really got to the basics...

Actually only two things really matter. Will your inverter run the appliance in question and will your battery support the inverter for a reasonable time without alternator input?

The reason I ask only these two questions is that your electrical system in this case may be thought of as a reservoir with a generating station at one end and a creek or river at the incoming side. As long as the reservoir has enough water to run the generator you're home free.

Bear in mind that the refrigerator will not run continuously. Assuming you run the engine and associated alternator you'll always be charging the battery. As long as your alternator can supply the required energy over time there will be no problem. Only when the continuous load exceeds the available input energy for whatever time it takes to discharge your battery will there be a problem.

Roughly speaking a 1500w load at 12.5v will equate to 125 amps. Assuming a 120 amp alternator running at idle speeds, line losses, inverter inefficiency, and heat buildup, the answer is that your system will not support the load in question indefinitely. On the other hand, considering the fact that the appliance will not run 100% of the time, I believe all will be well with your plan even if the alternator struggles to put out half its rated current.

In other words alternator capacity under the proposed arrangement is rather unimportant as long as it can supply the "reservoir" with enough energy over time to allow your inverter to work while still maintaining acceptable battery energy levels.

I hope this answers your question.

Our Passats have a 180a alternator. As long as the load from the car isn't super high it should run that inverter without issue.

-J

Gentlemen,

You continue to miss the point. I'd agree with you if no battery was involved, but that's not the case! The battery is what will run the inverter. As long as the battery is recharged before its voltage drops the inverter will be just fine.

It makes no real difference between alternator capacities, except time to recharge the battery. The appliance in question will not run 100% of the time. In between those run times even an alternator of modest capacity will bring the battery to full charge.

And so it comes down to time and total energy needed. As long as more or equal energy may be supplied to the battery over the total time of appliance use (running and resting), then all will be well.

Isn't the real question how much can the alternator put out at idle? The battery involved will certainly make up for the spikes as long as the idle output is high enough for the alternator to keep up off peek.

Oh, I misread that. I don't think the tiny battery in the car could keep a fridge running for long. I'd let the car idle.

-J

IMO Buy a $300 3500 watt Chinese generator from harbor freight...
Cheaper than burning out ONE automotive alternator....And the one I have had for 8 years has about 100 hours on it...No issues, try to keep the load at 2500 watt or less, the true rating on a 6.5 HP Genny with a inexpensive head....

Starts on the first pull every time I fuel it up...Just run it for 20 minutes every 6 months or so under load...Then shut of the fuel...Best to drain the cup you poured in to test it...But if you have some unleaded fuel preserved correctly...You get as long as 2 years, no issues.

You should not run that inverter without the engine running. The battery won't last long with a 1500 watt draw (or even a 500 watt draw, for that matter).

IMO you best option if you do the have much space is a "inverter generator".....They tend to be about 3x the price... But tend to be about 1/3 the size of the conventional units.
Honda makes the best....But you can get numerous"knock off brands" that have come out in the past few years for less. Likewise you could keep it stored, unused, with a can of special fuel that can even be stored in a car...It's $$, but safe to store....And about 2 gallons will get you the few days if run-time you want, combined with charging phones...
IMO do not use up your cars fuel...It's your escape plan....Just like do the to below 50% on a tank of fuel. Not convient....But if you fear "the big one"...Then you deal with it.

VeeDubTDI said:

You should not run that inverter without the engine running. The battery won't last long with a 1500 watt draw (or even a 500 watt draw, for that matter).

Click to expand...

If you plan to run an inverter straight off of a battery (no alternator), it should not be a car battery. A deep cycle battery would be the only way to go. You would need a battery that is designed to be completely run down and then be recharged. The batteries they use in cars are not designed to run refrigerators for any length of time.

Have Fun!

Don

JSWTDI09 said:

My question would not be how much current will my alternator put out (which is kinda what you are asking). My biggest question is how much current does your alternator put out with the engine at idle. I do not believe that your car will raise the idle speed to meet the needs of your inverter, so this may really be your limiting factor (unless you want to sit in the car with your foot on the go pedal while your fridge runs).

Have Fun!

Don

Click to expand...

The average car alternator is 90 amps, unless otherwise stated. So 90 amp times 12 volts is 1080 watts.

So based on this a 1500 Watt converter, even with the car running would create a deficit and drain the battery of 420 watts.

You would have to run the car for several hours WITHOUT the inverter working to replenish the battery.

You battery can handle 650 Cold cranking amps at peaks, you need to look at the AMP/Hour rating and make sure the 125 Amp draw by the inverter doesn't over draw on it.

TomB said:

The average car alternator is 90 amps, unless otherwise stated. So 90 amp times 12 volts is 1080 watts.

Click to expand...

According to post 8 above, the new (NMS) Passats have a 180 Amp alternator. That would be sufficient IF it can put out anywhere near that much with the engine at idle.

Have Fun!

Don

VeeDubTDI said:

You should not run that inverter without the engine running. The battery won't last long with a 1500 watt draw (or even a 500 watt draw, for that matter).

Click to expand...

Perhaps I was not clear. I know that. I would not expect my battery to last 15 minutes. My plan was to run the car for 3 hours, parked at idle, to let the fridge cool down.

Thanks for all the feedback. I guess if this was a good idea, then it would be part of everyone's disaster kit.

The little Honda Inverter Generator sounds interesting. Not sure how that is different than a normal generator. I will have to do some research.

I suppose that, with a can of gasoline with stabilizer mixed in might do. I'm not crazy about storing gasoline in my condo though.

And one warning.....A typical refrigerator usually needs more than 1500 watts to start...Called a surge...That's why generators typically have a "surge" rating....You need 2000 ways to reliability start a fridge that is full size...Sometimes MORE depending on age and size.... Remember running watts if different that starting surge.
Any item with a motor and a rotating mass needs extra watts in start-up.
Only things with restive loads, like electric heaters (no fan), toasters, and only filliment styleclight bulbs use a steady watts as rated....Other items use a large spike that tapers as the load drops.
Good luck...So.e items like "watt killers" or similar names plug into the outlet...Then you item into it...And you can read peak watts used.

One more time...

Keep enough water (energy) in the reservoir (battery) to run the generator (inverter) under load and all will be well. It's all about total energy needed and total energy available over time. Truth be told the system would work with solar panels as long as enough energy was available to recharge the battery while the appliance was resting and keep it over minimum voltage when the appliance was drawing current.

Most inverters will handle double their rated capacity for a short interval. Starting a refrigerator should present no problem. An inverter producing a square wave or even a modified sine wave should not really be a problem either, though it might cause the compressor to heat up more than usual.

Car battery vs a marine deep cycle battery? The inverter will shut down long before the battery is seriously discharged. Given that the battery will be continuously charged from the alternator even at a minimal rate, the health of the battery will not be affected.

Yes, the bigger (more amp hours) the battery the more robust the system. In other words the system could be expected to run at an energy deficit for a longer time than with a battery of less capacity. Balance energy needs with capacity over time and the system will work though there are far better ways of engineering such a system.

Consider an extra battery in the mix. Jumper cables from engine bay to second battery and the inverter hooked to the paired batteries. Your total storage capacity could easily be doubled. The rest will stay the same... Total energy needed over total energy available over time.

I went through this whole scenario after Hurricane Matthew left me without power. Long story short I bought a Harbor Freight Predator 2000 inverter generator. Long story, keep reading.

Fridge motors don't like modified sine waves so I first purchased Accurate Tools 2000/1000 pure sine wave inverter from eBay. $40.00

I have a boat with two batteries, one start/deep cycle and a deep cycle. I grabbed the deep cycle 27 group Interstate battery.

fully charged.. the inverter+battery can run my 26 cu.ft side by side fridge for 8 hours down to 50% battery or 12volts. The fridge would cycle 45 mins on/45 mins off. The fridge would pull about 300 watts when running.

With the VW running you could run this as long as you had fuel in the tank. I'm not sure the charging rate of the alternator to a dead battery but, I doubt it could put out 180 amps at idle, or an exhausted battery could take an 180 amp charge. I would recommend running the car for 1 hour every 2-3 hours.

After all this contemplating and researching online (wasted), I saw a good deal on a HF Predator Inverter Generator for < $300 (super coupon). 2000 max/ 1600 continuously. I have it outside and run a cord inside. It is not as loud as my loud diesel running and takes less fuel. At night if I want to keep the fridge running, I use my inverter and deep cycle battery combo. Then bust out the 10amp charger in the morning and use the gen to charge the deep cycle while it is running the fridge.

Ultimately, just give it a try, see what works best for your needs.

edit links
http://www.harborfreight.com/2000-p...c-portable-inverter-generator-carb-62523.html
http://www.ebay.com/itm/BRAND-NEW-P...327505?hash=item4d51786911:g:srMAAOSwygJXgW2f
SRM-27: http://www.interstatebatteries.com/m/category/marine/deepcycle

carlrx7 said:

I went through this whole scenario after Hurricane Matthew left me without power. Long story short I bought a Harbor Freight Predator 2000 inverter generator. Long story, keep reading.

Fridge motors don't like modified sine waves so I first purchased Accurate Tools 2000/1000 pure sine wave inverter from eBay. $40.00

I have a boat with two batteries, one start/deep cycle and a deep cycle. I grabbed the deep cycle 27 group Interstate battery.

fully charged.. the inverter+battery can run my 26 cu.ft side by side fridge for 8 hours down to 50% battery or 12volts. The fridge would cycle 45 mins on/45 mins off. The fridge would pull about 300 watts when running.

With the VW running you could run this as long as you had fuel in the tank. I'm not sure the charging rate of the alternator to a dead battery but, I doubt it could put out 180 amps at idle, or an exhausted battery could take an 180 amp charge. I would recommend running the car for 1 hour every 2-3 hours.

After all this contemplating and researching online (wasted), I saw a good deal on a HF Predator Inverter Generator for < $300 (super coupon). 2000 max/ 1600 continuously. I have it outside and run a cord inside. It is not as loud as my loud diesel running and takes less fuel. At night if I want to keep the fridge running, I use my inverter and deep cycle battery combo. Then bust out the 10amp charger in the morning and use the gen to charge the deep cycle while it is running the fridge.

Ultimately, just give it a try, see what works best for your needs.

edit links
http://www.harborfreight.com/2000-p...c-portable-inverter-generator-carb-62523.html
http://www.ebay.com/itm/BRAND-NEW-P...327505?hash=item4d51786911:g:srMAAOSwygJXgW2f
SRM-27: http://www.interstatebatteries.com/m/category/marine/deepcycle

Click to expand...

Wow... how is that inverter possible? 1000W pure sine for $35?

The last time I bought an inverter was for my mom's RV in 2011. It was 400 watts, modified sine for $45. I checked at AIMS, and their pure sine 1200W inverter sells for $189. How is your inverter over 70% cheaper. Weird.
http://www.theinverterstore.com/1200-watt-pure-sine-inverter-with-10-ft-cord.html

There is another Disaster Recovery idea I hadn't considered. Instead of genset running a battery charger like you have, use my TDI to run a charger instead of an inverter. That means I would only need to keep a deep cycle battery, inverter, and charger at home in the DR box.

If you find that running a 10amp charger is enough to top up your battery once a day, then I wonder how that would work of I power the charger from the car? That charger would put out in theory 120 watts. But in reality I would expect it to be closer to 100 watts top. The problem is finding a 10amp charger than runs on 12v DC from the car.

The alternator on my Passat is rated at 180 amps. If I have a 10amp charger plugged in, then that should be no problem.

To recap the new idea:
(1) Two sealed AGM deep cycle batteries in serial.
(2) 1000W/2000W peak 12v inverter.
(3) 10 amp 12VDC charger.

Yankinwaoz said:

Thanks for all the feedback. I guess if this was a good idea, then it would be part of everyone's disaster kit.

The little Honda Inverter Generator sounds interesting. Not sure how that is different than a normal generator. I will have to do some research.

I suppose that, with a can of gasoline with stabilizer mixed in might do. I'm not crazy about storing gasoline in my condo though.

Click to expand...

A little Honda EU2000i will serve you well. It's small, quiet, and very thrifty on gasoline consumption.

Instead of the Honda, I found this.
http://www.championpowerequipment.c...204-2800w-3100w-dual-fuel-inverter-generator/

It is the same price as the Honda ($1k), but I can run it from a propane tank or gasoline. So if I end up with a gasser after Diesalgate, then I will get a small handpump to steal gas from my car's fuel tank if I need it.

Yankinwaoz said:

Instead of the Honda, I found this.
http://www.championpowerequipment.c...204-2800w-3100w-dual-fuel-inverter-generator/

It is the same price as the Honda ($1k), but I can run it from a propane tank or gasoline. So if I end up with a gasser after Diesalgate, then I will get a small handpump to steal gas from my car's fuel tank if I need it.

Click to expand...

That's pretty big....If you are worried about size most inverter generators are much smaller...And the more $$ you spend, typically they get more quiet...The Honda's can Litterly run about 15 feet from you and not be annoying...

Yankinwaoz said:

Instead of the Honda, I found this.
http://www.championpowerequipment.c...204-2800w-3100w-dual-fuel-inverter-generator/

It is the same price as the Honda ($1k), but I can run it from a propane tank or gasoline. So if I end up with a gasser after Diesalgate, then I will get a small handpump to steal gas from my car's fuel tank if I need it.

Click to expand...

ZippyNH said:

That's pretty big....If you are worried about size most inverter generators are much smaller...And the more $$ you spend, typically they get more quiet...The Honda's can Litterly run about 15 feet from you and not be annoying...

Click to expand...

Champion makes good generators, however the one you linked to is not an inverter generator - so the engine speed will be continuously at 3600 RPM. Not as clean power either but your fridge won't mind. Having the dual fuel is nice as you'll be able to run longer on a tank and you don't have to worry about old gas.

The inverter Honda is a nice unit but sometimes even starting a fridge can be a problem. I have an inverter Yamaha EF2000 and in eco mode it cannot start my fridge (the engine bogs and before it can ramp in speed the thermal cut out on the fridge starter trips). If I turn off ECO mode, engine runs faster and starts the fridge fine. Such a bummer as the fridge running only consumes 140W (defrost cycle is 700W BTW).

If SHTF, solar panels are cheap these days. You can get 24V panels over 200W in size for about $0.65/watt. Silent, makes power in the daytime, but you'll need a battery bank for night. Still, your neighbors will be much happier though you will have some panels out in plain view.

BTW, I've been 'preparing' for a disaster for a few decades. Nothing exciting happens here in So. Cal. My power has been out at most 15 hours due to a transformer explosion. Keep the fridge and freezer closed as much as possible and you're fine.

JSWTDI09 said:

According to post 8 above, the new (NMS) Passats have a 180 Amp alternator. That would be sufficient IF it can put out anywhere near that much with the engine at idle.

Have Fun!

Don

Click to expand...

Hmmm. My 2015 Audi A3 has only a 140 Amp.

You would have to find an alternator with a much larger voluminous magnetic path. Then you may fathom out the following. Note that you cannot step up neither the power nor the energy.
1. You can use a DC to AC or DC inverter to step up the voltage.
2. You can take the rectifier off and use a step up transformer to obtain a higher voltage then process it as required.
3. You may run a suitable motor generator.
4. You may rewind it to give you the voltage required
Note that as far as the frequency is concerned a car alternator does not work at 50/60 hertz so simply saying that you need 240 Volts at 1500 Watts is really not enough information.
An engineer would improvise the right set up and equipment to obtain what he wants, but it is not always economical nor worth the effort. But knowledge how to do things and succeed in doing them, is always good for one's soul and spirit.

FWIW, I ran a full size fridge and a deep freezer off a $500 Harbor Freight Predator 2000 inverter generator for about 40 hours a couple of years ago when we had some tornadoes. Actually I shut it off at night but it was enough to keep the food from spoiling.

I had heard good things about the generator and I was impressed with how well it worked and how quiet it was.