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When our electric power went out 2 months ago, I started thinking about emergency power. Our outage was unusually long, 2 days, because lightening hit a tree w

When our electric power went out 2 months ago, I started thinking about emergency power. Our outage was unusually long, 2 days, because lightening hit a tree which fell on our overhead power lines to the house and pulled down all the lines, conduit, electrical boxes, etc. Got a little electrical meter and showed that usually my office (I'm writing software) uses a grand total of 55 Watts, maybe 100 W if I do more, maybe 1000 Watts if I use the laser printer, boot my tower case Web server with several hard disk drives and an AMD 8 core processor, a little more in the kitchen for the refrigerator and occasional use of the microwave oven and toaster, a little more if I want to keep the winter heat, fueled by natural gas, going. For the hours of an outage, I'll f'get about running the air conditioner, oven, washer, and dryer. Soooo, I can get by at 50 Watts and can do pretty well for a few days at peaks of 2000 Watts and an average over time of likely under 1000 Watts. Okay, and I have a car! Yup, a car has an engine and generator, both very well designed! A little shopping shows that I can get a box that will output 3200 -- 15,000 (in steps of about 2000) Watts, a different box for each step of 2000, of US standard 60 Hertz (Hz, cycles per second) A/C (alternating current, with a good approximation to the standard sine wave) at 120 Volts from any 12 Volt DC (direct current) storage battery. Just clip two leads onto the battery and run extension cords from the output of the box and keep the electrical loads I mentioned running. So, I could get a box that can output 4000 Watts ...! And I have a car! Hmm. Soooo, back the car out of the garage, raise the hood, set the box on a front fender of the car, attach the two leads from the box to the car battery, start the engine, just let the engine idle, run the extension cords from the output of the box to my office, kitchen, and, maybe, natural gas powered furnace, and, ..., check the amount of gasoline in the car's tank! Since I don't need much power, the car and the box would keep me going for a few hours or ~2 days of an outage. Uh, ..., don't have to be very inventive because there is something of an industry serving people with campers, trailers, off-grid cabins in the woods, etc. who do a lot with getting power from batteries, gasoline powered generators, etc. In short, just clip two leads onto the car battery, start the engine, let it idle (the car knows how to keep the battery charged without overcharging), run the extension cords, and wait for the local electric power utility to get the outage fixed! For the horrors of back feeding power to the whole house and maybe electricuting utility workers, etc., "no worries, mate": Are NOT trying to power the whole house. Instead, are just powering a few loads with extension cords. E.g., my office loads plug into the female sockets of a power strip which plugs into the wall. Soooo, just unplug the power strip from the wall and plug its male plug into the female socket at the end of one of the extension cords. Same for each of the microwave oven, toaster, refrigerator. For the electric power used by the natural gas powered furnace, that will have to be a little more involved. But, again, are just running the electric loads much like would on a camping trip. "No worries, Mate!".

seabrookmx 3y ago
If the car's alternator is for example, 100A like it is in my car, that means the maximum output is 1200w. So if you use a 2000w inverter you'll be draining the battery at peak load. Just something to keep in mind so you aren't stuck with a car that won't start (or even run if it gets too low, as the fuel injectors will have too little voltage to fire).
- graycat 3y ago
  Thanks for the alternator current of 100 Amperes and 1200 Watts -- I didn't have that data! If I run the battery down, then I'll just have to wait until the electric utility restores the power! Then I'll have to recharge the battery! For that, I do have a battery charger. Curiously, the battery charger puts out only 14 Amperes!!! The charger and a lot on this whole subject has lots of warnings about how fast should charge a car battery -- their advice is to charge slowly or damage the battery, ..., explosions, etc.!!! Ah, they didn't get to college like I did: Had an old Chevy, stick shift. Somehow, too often, when I tried to drive to college for the first class, the battery was dead. Hmm .... Well, the driveway went downhill a little to the street. Sooo, with the door to the driver's side open, I stood by the steering wheel and got the car rolling rolling backwards downhill -- jumped in, closed the door, and aimed the car in the downhill direction on the street. Again with the driver's door open, with the transmission in neutral, got the car rolling downhill, reached in, swatted the shift lever down to engage 3rd, High gear, kept pushing, and right away the engine tried to start but, with 3rd engaged, struggled. I jumped in, pushed down on the clutch, put the shift into Neutral, gave some gas, pulled the door shut, and drove to class! After about the 15 minutes of driving to class, the battery was nicely enough charged to start the engine -- the dead battery problem was solved until the next dead battery problem! Lesson 1: If listen to the usual rules of safe operation of a car, won't get to class on time! Lesson 2: Can give a battery a nice charge quickly, e.g., 15 minutes! Another issue: At one point I did discover that the battery charger won't do any charging at all for a fully dead battery. So, I just got a laboratory style DC power supply and used it to give the dead battery an initial charge and then used the charger intended and finished charging.
rft 3y ago
tl;dr: This setup worries me a bit, maybe talk it over with someone qualified in this, e.g. electrician, off-grid electrics expert. At 4000W you are looking at around 300A on the 12V side. This requires chunky copper and clamps. Keep in mind the already quite big cables to jump cars are only rated for very short usage. Not saying it can't be done, but this amount of current certainly worries me. Then you have the issue of protecting the 120V loads. You can get more than 20A of current out of the alternator, which pushes what you can safely put through standard extension cords. Usually running a single device off an alternator or generator is fine, but once you have multiple devices, hooked up to power strips, you can run into failure modes (with defective devices) that can cause shocks.

seabrookmx 3y ago

If the car's alternator is for example, 100A like it is in my car, that means the maximum output is 1200w. So if you use a 2000w inverter you'll be draining the battery at peak load. Just something to keep in mind so you aren't stuck with a car that won't start (or even run if it gets too low, as the fuel injectors will have too little voltage to fire).

graycat 3y ago
Thanks for the alternator current of 100 Amperes and 1200 Watts -- I didn't have that data! If I run the battery down, then I'll just have to wait until the electric utility restores the power! Then I'll have to recharge the battery! For that, I do have a battery charger. Curiously, the battery charger puts out only 14 Amperes!!! The charger and a lot on this whole subject has lots of warnings about how fast should charge a car battery -- their advice is to charge slowly or damage the battery, ..., explosions, etc.!!! Ah, they didn't get to college like I did: Had an old Chevy, stick shift. Somehow, too often, when I tried to drive to college for the first class, the battery was dead. Hmm .... Well, the driveway went downhill a little to the street. Sooo, with the door to the driver's side open, I stood by the steering wheel and got the car rolling rolling backwards downhill -- jumped in, closed the door, and aimed the car in the downhill direction on the street. Again with the driver's door open, with the transmission in neutral, got the car rolling downhill, reached in, swatted the shift lever down to engage 3rd, High gear, kept pushing, and right away the engine tried to start but, with 3rd engaged, struggled. I jumped in, pushed down on the clutch, put the shift into Neutral, gave some gas, pulled the door shut, and drove to class! After about the 15 minutes of driving to class, the battery was nicely enough charged to start the engine -- the dead battery problem was solved until the next dead battery problem! Lesson 1: If listen to the usual rules of safe operation of a car, won't get to class on time! Lesson 2: Can give a battery a nice charge quickly, e.g., 15 minutes! Another issue: At one point I did discover that the battery charger won't do any charging at all for a fully dead battery. So, I just got a laboratory style DC power supply and used it to give the dead battery an initial charge and then used the charger intended and finished charging.

rft 3y ago

tl;dr: This setup worries me a bit, maybe talk it over with someone qualified in this, e.g. electrician, off-grid electrics expert. At 4000W you are looking at around 300A on the 12V side. This requires chunky copper and clamps. Keep in mind the already quite big cables to jump cars are only rated for very short usage. Not saying it can't be done, but this amount of current certainly worries me. Then you have the issue of protecting the 120V loads. You can get more than 20A of current out of the alternator, which pushes what you can safely put through standard extension cords. Usually running a single device off an alternator or generator is fine, but once you have multiple devices, hooked up to power strips, you can run into failure modes (with defective devices) that can cause shocks.