Use of Vehicle as a generator in a pinch...??

Discussion in 'Survival/Preparedness Forum' started by Contact, Nov 15, 2012.

  1. I figured I'd throw this out there and see what everyone thought about it, I'd like some feedback on it, and if it's a decent plan, it might even be something for other people to consider.

    A few years ago my work switched vendors, and we ran a clearance sale on our power inverters. I got an amazing deal, and was able to acquire 2 800 watt inverters, and a few 400 watt inverters for less that 50 bucks for all of them if I remember right.

    The 400 watt inverters can either be connected directly to the battery, or plugged into a cigarette power source, while the 800's must to be connected directly to the battery.

    So, onto my actual question, my vehicle has a 125 amp alternator, and since everyone seems to agree that inverter generators are the way to go if you can afford them, is there any reason the vehicle couldn't/shouldn't be used for backup/emergency power for a temporary loss of power? Obviously the car would use exponentially more fuel than a dedicated generator, but if you only need it for a couple days and you have a good running, reliable vehicle, it could prove useful.

    Moreover, is there a limit to how many inverters I can plug up? I don't know how much a 125 amp alternator would safely run if the car is just sitting there idling with most of it's own accessories turned off. I know with the 400 watt inverters, the limit would be on the actual circuit that it's plugged into, but for the 800's, they would be connected directly to the battery, so as long as the car is running, and the battery stays charged, they should be fine.

    This is definitely not my long term survival strategy, as a car would use its gas up in a matter of a couple of days depending on how much we needed to run it, but since we just made the investment of a new home a few months ago, we haven't had the extra disposable income (or the need, luckily we've had no power outages) for a dedicated generator with transfer switch, but I think as long as I kept it modest with the stuff we needed to run, I think it could work.

    So I guess the point of this thread is to lay out my current primary plan for a friendly analysis, and if nothing else, this primary plan could eventually be my Plan B once I get a dedicated generator for the house. I am fortunate that the home we purchased had to be completely remodeled after a fire a few years ago, so all of my appliances are newer energy efficient appliances. I also wonder if there would be any way (or need) to hook my 800 watt's together to give them a 1600 watt capacity to run some of the larger appliances or a space heater if necessary. Obviously the major concerns would be to run the fridge, and washer/dryer.

    Let me have it!!

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  3. First things first, what all are you planning to power? Often the cheaper inverters are very optimistic about their wattage rating. Grab a kill-a-watt meter and do some testing.

    Secondly, you would probably need to install a high idle circuit in the vehicle. Extended idling is bad for engines. Commercial (f-250 and up) trucks are going to be wired for this, at least last time I checked they were. If I recall my 7.3 diesel had a wire for 1200 rpm and another for 1300 or 1400rpm, again it's been a while.

    Lastly, I'm no electrical engineer (my dad is though). Putting two AC sources together would require that they be in perfect phase or they will drift, the voltage will drop and both of the units would fry trying to fight each other. So, not a good idea.

  4. Great feedback! If I had to resort to just using the car, my intent would be mainly heat, laundry capabilities and running a fridge. I do own a Kill-a-watt, I'll have to get it going and see what kind of power they draw. As I said, I know they are all energy star rated, but I'm sure the compressor for the fridge kicking on would be more than 800 watts unless my new fridge is significantly better than my old one. IIRC, the old one kicked up to around 1800 starting watts, and then dropped down to around 700 or so, so there'd be no way to use the fridge with any of them. Also, since the furnace is hardwired like usual, it's not like I can plug it into the inverter, so I would have to resort to a room space heater, which uses about 1300 watts while running.

    Interesting idea on the high idle circuit...I don't know how easy it would be to do on a newer car that's not wired up for it. It might be easier to get a length of wood to wedge between the pedal and something else to keep the pedal depressed to a set rpm.
  5. Inverters draw alot of juice. Remember that wattage = amps X volts. So if you are drawing 800w at 12V, that means it will be sucking at least 66.66 amps per 800w inverter at full draw. Plus, you have to figure in that your inverter is not 100% efficient, so it's not unreasonable that it could draw as much as 100 amps at full draw. At this point you are approaching the capacity of your alternator. So for our purposes, let's just say that your alternator will be good for about 100A (will give us a 25A safety cushion for the vehicle's electrical draw-onboard computer, etc).

    Now, it IS possible that you could run two 800w inverters at once knowing that you would draw down the battery at the rate of 66amps. So, if you figure that a starting/deep cycle group 24 battery will have only about 90 amp/hours of storage capacity (on the generous side), that means you will draw the battery down to 50% charge (electrically "dead") in about 40 minutes. You would then need to shut down the inverter long enough to charge up the battery again. So assuming again you can put 100A back into the battery, it will take you about 30 mins or better to charge the battery back up (maybe more). So you're looking at 40 mins of on time, followed by 30 mins of off time. That gets you about a 75% duty cycle using both inverters at once. Not bad, but not great either. I'd say you could probably run one 800w inverter constantly and be OK.

    Above it was mentioned about the phase of the inverters, and having them fight each other. This is partly true:

    The input (the "draw") for the inverters from your 12v system is DC - direct current. Two inverters can connect to the same 12v source no problem - the current does not alternate, it flows the same direction all the time, so there is no "phase" difference to worry about.

    The output (the 120v side) IS alternating current - 120v, 60hz. You CANNOT plug the outputs from both inverters into the same circuit, but you can run the inverters individually. In other words, if you fab up a way to plug both inverters into the breaker box on your home, you ARE going to have problems and probably blow up the inverters. However, you CAN run an extension cord from inverter #1 to your TV, and another SEPARATE extension cord from inverter #2 to your satellite reciever, and you will be good to go. But if you somehow gang both inverters together into the same power strip (or other circuit), bad things happen. Think of it like one proton pack with two "guns" attached. It's OK to run both guns off one proton pack, but DON'T CROSS THE STREAMS!

    Clear as mud?

  6. Based on what you are describing, you are NO GO.

    Forget running a heater off the inverter. You're losing massive amounts of efficiency by changing types of energy - changing heat to mechanical (in the engine), turning mechanical to electrical DC (alternator), turning electrical DC to electrical AC (inverter), and then from electrical AC to heat (electric heater). You are losing probably 95% of the heat energy of gasoline by doing this. It's like going around the block to go next door. You would be WAY more efficient to get a small gasoline burning heater (like one of the old korean war era USGI stoves)

    If the fridge draws 1800 starting watts, that's how big of an inverter you'll need. Something like a 1500w continuous / 2000w peak inverter would do the trick. Because the instant you exceed the output of the inverter, it will trip an internal fuse or breaker, and it will put out ZERO until it cools back down enough to reset (or until it is reset manually). And you CANNOT gang up two inverters to handle the load due to phase differences.

    Laundry, you could run the washer OK I would bet, but unless you have a gas dryer, you will not be drying laundry (same reason as heater above). There's a reason electric dryers use a 220v plug - because you can't push enough juice through a 120v plug safely to run that kind of wattage.

    Most appliances have the "electricity input" tag on them somewhere on the back near the plug. It will say something like "120v at 2.5amps", and from that you can figure out the wattage. The above example would be 300 Watts (120*2.5). That should give you a ballpark idea of what you can run and what you can't.

    And don't forget about the duty cycle. Your alternator, putting out 100 useable amps, is only going to be good for about 1200 watts continuous. Go above 1200 watts, and you're going to have a reduced duty cycle.
  7. If you get a larger output inverter, you could concievably run the fridge for a brief burst (while drawing down the battery), and then shut off the inverter while the battery charges. The insulation in the fridge would keep food cold until the battery could get caught back up enough to run the inverter for another burst to keep the temp down.

    Either way, you're going to want a bigger inverter for what you're talking about. Harbor freight has some good deals on them... I got a 3000w inverter for less than $150 a couple years ago. Might also be worth investing in a "dual battery" setup for your vehicle - it wouldn't increase your duty cycle, but it WOULD increase the time period of both the inverter draw and recharge time. I.E., instead of running the inverter for 10 mins, then recharging for 10 mins (switching back and forth every 10 mins), with two batteries you would only have to switch from draw to charge every 20 minutes. Would make it so you could do other stuff while doing this... instead of having to have someone "babysit" the setup and switch over constantly.
  8. If you want more info, check out some RV forums. Those guys know about inverters, battery capacity, and the like. It's where I learned.
  9. From my understanding alternators do not produce full power at idle. I believe most is around 1500 to 2000 rpms before they make full power.

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  10. So it looks like, based on the information I got so far, that I could use the car as a temporary power source to recharge equipment that I don't have car chargers for, and may be able to run the washer and dryer (I have a gas dryer) but other than that it would probably not be feasible to use it for heat or to keep foods cold.

    I would consider it a waste to use the car to run a few lamps or anything like that, if I were to be using gas from my car, it would have to be for something substantial and necessary such as the things I've mentioned.

    But, I've always wanted to learn about electricity, so this thread will still be helpful!!
  11. Your understanding is correct.
  12. I suspect even a washer would be too much load (motors have a large startup draw). A gas dryer might be ok. Check the plate on the units, they should have current draws specified?
    #11 cowboy1964, Nov 15, 2012
    Last edited: Nov 15, 2012
  13. I have two generators that I use for my work One is a 2200 watt and one is a 5000/6500 watt. I plugged the fridge up to the 2200 watt generator thinking it would power it and it barely did it, it did not shut the generator off but you could tell it was almost under full load while running.

    My 5000 watt one was about $599 from home depot and the 2200 watt one was $329 and from Northern Tool and that includes a 5 year no questions asked warranty. They said if it breaks bring it back and get a new one. I have had the 2200 for about 10 months and the 5000 for 2 years both have been good and I use them almost everyday.

    I used to work for a guy who had a GMC 2500 and had a 3000 watt inverter wired directly to the battery. I used it a few times to run a skil saw and the saw would bind up because it did not produce enough power.

    I would not use an inverter for these purposes.
  14. Tractor supply had a 2000w gas gen on sale for $100. Get that.

    Running a vehicle isn't worth it...the fuel use with the idle rigged to run at a higher rpm would not be good. I believe the old estimate for stuck in traffic idling is 1/2 gallon an hour.

    The cables, alternator, batt may be able to source high current, but pulling 50-60 amps at a 100% duty cycle is "probably" not a good idea.

    In an emergency for a few hours, fine.
  15. LongGun1

    LongGun1 StraightShooter


    1st....lots of good advice! :thumbsup:

    I would consider a different path than the one you are currently on..

    A little background on myself...

    My educational background is electronics engineering, military experience primarily was in electronic communications, my current career is in industrial electrical/electronics/process automation/robotics, I have a side business dedicated to backup power, also I attend renewable energy industry expos, seminars, subscribe to industry publications, etc

    Pictured below is the completely automated 8 KW (20 KW Surge) 120/240 sine wave inverter/charger setup I installed & configured in the NE La home...(my other backup setup of 20 KW {44 KW surge} Exeltech MX Inverters is in N Arkansas)

    ..will automatically transfer power from a failed grid to battery powered inverter backup in a fraction of a second..

    .. & it has been providing seamless backup power for my family since the late 1990's...


    AC power sources for the Power Panel are an 8 KW (24 KW surge) fuel efficient, low-rpm Diesel genset..

    & the Grid..

    For the DC side...this 16 ea. "Golf Cart" battery configured 48 VDC DC Battery Bank (17 KWH usable at 80% DOD) shown here being replaced in early 2006 (still on this 2nd set)


    Now for the advice...

    ..rather than trying to pound a square peg into a round hole with the gear you currently have..

    (possible carbon monoxide issues with running a vehicle for extended periods with accelerated wear, possible damage to your vehicle electrical system {inverters like you describe are designed to convert DC on a short term basis from batteries to 120 VAC used for low power electronics & such, not high power devices like heaters/dryers/etc...not to invert 12 VDC from alternators...and the best batteries for this use are deep cycle...not starting batteries} ,wasting precious gasoline, large power losses/inefficiencies in a inexpensive 12 volt inverter setup, possible damage to your new appliances with modified? sine wave inverters, attempting to sync & stack inverters likely not designed for that purpose, possible invalidation of insurance coverage with a jury rigged non-UL rated setup, possible long runs of expensive heavy gauge copper wiring needed for minimal voltage drop with a 12 volt system, lots of effort expended for little gain, possible dangerous environment for family members or non-knowledgeable others attempting to energize components in an emergency, etc )

    ..why not sell the gear you have ..

    ..& work towards a setup (like the one pictured above) that will work well for your purposes?

    If you have a tractor...especially a diesel one..

    ..there are PTO generators that will work well for providing backup power.

    Also, there are welding rigs that also work very well as a whole house generator.

    Either of the above can be integrated with an battery backed inverter/charger to have an automated backup power system.
    #14 LongGun1, Nov 16, 2012
    Last edited: Nov 16, 2012
  16. BR549

    BR549 Thread Killer

    I cannot remember how old those pictures are...:whistling:

    ...but that picture from ? years ago pushed me to complete a variety of similar setups to run various houses/barns/garages/camps I own...

    ....however, mine are not the same beause I have certain things that are always run by solar/battery and certain things to which the solar/battery backup are not connected...

    ...running something fulltime by solar/battery will teach you how long different components can/will last...

    .......also...a generator can be used to recharge the batteries......but the sun is less noisy....

    ...Thanks ehljeewhahn............:wavey:
    #15 BR549, Nov 16, 2012
    Last edited: Nov 16, 2012
  17. RWBlue

    RWBlue Mr. CISSP, CISA

    I have kind of wondered the same thing.

    Where my parents live the power has gone out in winter for an extended period of time once every other year. For the most part it isn't a problem, BUT there is always the concern for water pipes freezing. What would it take to hook up their GMC Yukon to the Gas furnace in the house? I assume if they heat up the house once a day or once every other day the pipes will not freeze.

    Second question:
    Assuming I get a truck camper and decide to camp not in a camping ground, what would you recommend for an inverter and what could I power? Can I run the AC in the truck camper? Can I run the microwave? I do not have a truck camper at this time, so this is just part of the deep research for the plan.
  18. Since I'm the one who was here asking questions, I'm probably not the most reliable source of information. :supergrin:

    But I will say that my entire 42inch plasma tv, xbox, dvd player setup uses less than 300 watts, however what I've found is that anything that creates heat or cold, uses exponentially more power than anything that just runs steadily. For example, my Keurig coffee maker uses about 5 watts just sitting there, but while it heats up the water it jumps up to around 1350 watts, give or take. My toaster uses about 1600 watts while heating.

    I know most of the microwavable products give their directions based on a specific wattage. I've got some frozen burritos in the fridge now that say they are based on 1100 watts, so I'd bet that's about an average give or take a couple hundred watts. Of course the smaller the microwave, the less watts it uses, and the longer the food would take to cook.
  19. Temp emergency power? Buy a cheap genny...done.

    The batt, gen, inverter combo gets the bonus denying that, but the cheap and easy solution is a champion generator for $300-$500. If you want the inverter system your talking 3000-5000 and least....and you still bought a gen to recharge your batteries!!!!
  20. RWBlue

    RWBlue Mr. CISSP, CISA

    I understand what you are saying. I have used a Killawatt and played with my small inverter to power things like a laptop. I have the one in my vehicle out so I can power a tablet and track were I was going.

    The key for my parents is that they would ONLY be powering the fan, not producing the heat.

    The key for me is that other people doing the truck camping thing should have already worked this out. I just have to find one who can tell me this is how it is done (inverter or generator).
  21. I'm rockin' a truck camper, and while it is self-contained (fresh water and wastewater tanks), it is not very "electrically complicated.

    It's pretty old, so it has no microwave. The only thing I have that's 120v is the Air conditioner, and it's a 5K BTU household window-mount unit that I fabbed up a bracket to stuff it in the back window. I also have a 3000w surge inverter from harbor freight. Even though my math says the inverter *should* start the AC, it trips the breaker on the inverter when the compressor kicks on with the window unit. I am suspecting I need a better cable from the invert to the battery, as I was merely testing it out with jumper cables at the time.

    You're going to need a 4kw genset to run either the microwave or small A/C, and alot more to run both at once.

    For cooling a truck camper with little electricity use, I suggest a roof-mount swamp cooler. Mine has an old RecAir unit, but the company was bought out and is sold now at . The swamp cooler only has a couple of amp draw to run the fan, and the cooling is done by evaporating water. So basically, with a 12v battery and a couple of gallons of water, you have a cool camper. I have a single walmart deep cycle group 27 battery, and it runs the lights and waterpump on my TC all weekend. I'm not wasteful, but I'm not super careful either. I usually run out of water before I run out of battery. And if the bat runs down, I could charge it off the pickup. I think with a roof mount harbor-freight panel, it would make the battery last 4-5 days before being depleted. If you could hook up to water and sewer, such a setup would probably get you though a disaster.

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