I just want to say one thing.

Fuses,fuses,fuses,fuses and more fuses. You would not want to repeat the burning wire thing in the car as the burning wire thing in the house. Fuses need to be just a pinch higher amperage of each circut you build and they must be located at the battery power source and both on the power going in and out of the invertor. Make surew wire sizes are big enough for there load. There are wire ga. load and distance charts on the net.

Your perants may not give a second chance on there house.

Good luck and keep up that enthusyazym (spelling?).

                       JK TAS Jerry

Airheads Page

i would go back the the 5hp engine and alternater idea trying to use a car is going to end in car repair bill round 2.

Buy yourself a few deep-cycle batteries and a marine "float" charger. Car batteries are utterly destroyed by deep-cycling. They're only built for short-duration, high-current loading, then immediate recharge.

Wire all the batteries in parallel with a heavy buss cable and connect the charger to those with solid bolted connections (no suprise arcing from battery clips)

A 100ah battery will allow you 5amps (75 watts) continuously for about 15 hours without damaging the battery. Mulitiply that by however many batteries of the same kind you wire into that parallel bank. Those are about $60 each from wallyworld.

Based on those numbers, build it large enough to get you through blackout periods without needing any outside generators.

Then just recharge the bank when the power comes back on.

Add a small generator to recharge the bank during extended blackouts.

First though I am not familar with your country, pricing, or whats available to you.

"I started by hooking up an old APC UPS rated at 300w to the car battery, and running the car so I would get the power from the alternator. This worked quite well, and, by running an extension cord out the window to the car, I was able to power a couple lights. This worked for very short time periods,"

 You say 4 lights? How many watts was that? Also it's not good to idle a car engine for long periods plus all that waisted feul.

You might just want to take the easy way out on this. Take a nice large UPS (I have a 600watt) and connect that to  several deep cycle batteries. When grid power is on your UPS is running on that and charging the batts., When grid power is off you have the UPS running on the fully charged batteries. No problem switching stuff. Make sure you wire the UPS to the correct voltage of batts. Mine is 24Vdc so I have 2 batts. each 115 amps wired for 24v which is still 115amps. If you decide you need more time, then wire in more batts. in my case two at a time.
 I also have much larger Ups's here, but I only do that with the 600watt one for now.

I also have a 5,000 watt/10,000watt surge Aims inverter and other  battery systems for it.

Basically since your not wantng to get off grid and make your own power like many of us, just wanting backup power, I would say stick to the UPS systems. Get larger ones and several of them. Should be cheap if you can find them used needing batteries. Then you have the charger/inverter and instant switch between grid and batts. Add your own deep cycle batteries to each one. Then you also have the choice of which to run things off of. Maybe one UPS for the computer only, another for a light, stereo and a clock. Heck you could even have one in each room if you wanted, and no problems wiring, just put batteries outside and run the 12v wires of heavy enough size and a fuse, plug into wall and forget it. Figuring each UPS has it's own battery set. Otherwise you could also run one larger set of batteries and run wires from that to each UPS. Run them all fromthe same batt. bank, but that might be more problem as you would need heavier wire for longer runs, might have to disable the chargers in some UPS's ect...

Car batteries as others have said are meant to be kept fully charged all the time basically. They give out a little power to start the car and then go back to full charge where they should stay. Basically when everything is working correct and the engine is runing you don't even need the battery in the car! The car runs from the altenator, not the battery. The battery is kinda a buffer, takes the juice and stores it, and supplies extra durring surges till the altenator catches up. Take the Hot wire off the battery when the car is running and it should keep running unless you over load the charging system. I have driven many cars without Batteries, push start a manual transmision car and start it in gear and go.

Deep cycle batteries like for trolling motors on fishing boats and other types are meant to be charged for awhile, then used long periods without charging. Like a trolling motor, you charge over night then use it alot while fishing durring the day, then charge again that night. Deepcycles are built heavy inside to handle that type of use, car batts. are not!

As for your Idea of using the Brigs engine and an Altenator for a generator, that is a good idea! I have done that myself. I suggest taking the exhaust and making a better muffler to quite it and use that. For one thing running a car engine is going to use way too much gas for the power you'll be getting. The small briggs engine will produce plenty of power but really use far less feul! Many cheap fast easy ways to quite that too. Connect a pipe to the engine exhaust and run it into a heavy plastic barrel of dry loose sand. The sand absorbs much of the noise, it's loose so the exhaust passes right through. Maybe just run the pipe into a barrel of water, that works too. Just make it below the engine, you don't want to suck water into it if a valve sticks.

As for the vibration though. Many motors of that type use the blade weight as a flywheel, if off a push mower could have been your problem. Use a heavy pully bolted where the blade used to be, or use a riding mower type engine which might be better. Mine was a 12hp riding mower engine. If it was a horizontal motor like for a minibike or gocart it should not have had much vibration anyway. Bolt it all nice and tight to a frame. For mine I used a braket I made for the altenator, it had one bolt to the frame to hold it in place on one side and a very heavy spring on the other side to pull it tight against the belt. Easy to remove or adjust when I was palying with things. Course there were other parts to hold it lined up that it slide against.

"I need to find someway of turning the 400 watt inverter into a UPS, for my computers, and I need to create a circuit that turns the florescent lights on when power goes"

 I would suggest getting a real UPS for the computer. Wire the 400watt inverter to battiers and just turn it on and off as needed. As for the instant on lights, take a
light sensor like turns on the outside lights at night and connect the lights to that. Put the sensor in a dark box, connect to the UPS. Then take a small light (smallest low power you can get)and put that in the box with the Senser and plug it to the wall. When grid power is on, light is on, senser sees light and flouresents on the UPS are off. When grid power goes off, light goes off, senser is in dark and turns on the UPS powerd lights.

Good luck, be creative but be safe, and have fun!!
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nothing to lose

   Wow, cool man.  

   You know, not to try and divert attention from this site but i would like to see you @ my site.  The reason for this is my main goal is to bring alternative to mainstream. People in your age group are one of my 'targets'. Im 26, so im not tooo far off. hehe

STOP WHATEVER YOU'RE DOING AND FIRST STUDY THIS STUFF

You are very likely going to get yourself either hurt or killed the way you are going about it. I'm all for experimenting, but batteries, crappy power lines, UPS's and running car alternators do not mix very well when you're experienced, when you're inexperienced you're likely to end up as a darwin award nominee.

Please trust me on this, I have been where you are right now, being 15 and pulling all kinds of crazy experiments. But at least I had a solid understanding of the basics and how to operate safely and from your words I gather you really do not.

Find yourself a friendly neighbourhood ham and become his disciple, he'll be more than willing to teach you whatever you want to know.

If all you want is to be able to deal with power outages, go buy a generator and have it wired in by a competent technician.

If in spite of this advice you want to push on with your unsafe activities, at least go visit a lawyer or notary public and leave a will.

good luck