How can I make backup power supply w/ a car battery & a plug strip?

[ZapZilla]

Seriously, I already have a large capacity car battery, a charger, and a plug strip.

How can I make a backup power supply for my computer with this stuff and what else would I need?

I know I'll need a transformer and I'm sure that Radio Shack has one to switch from DC to AC.

Is this a feasible idea that could be less expensive or better than a commercial solution?
Or should I just go buy a commercial solution for big bucks?

As I live in San Diego, CA I am expecting many future power outages and a nice battery power backup would be a good thing.

Thanks in advance.

 

[Windogg]

A couple of idiots did that afew weeks ago on another site. Just get a regular UPS. It's more than just a car battery hooked up to you computer. UPSes are actually very sophisticated and specialized. They regulate and filter the power coming into your PC. Better models will even save open documents in the event of a power failure. Plus there is the safety concern of having a lead acid battery giving off hydrogen-sulfide under your desk.

Windogg

 

[Thegonagle]

Either buy a power inverter ($60-80 for a 500 watt model should be fine) and hook it up to the car battery, or buy a UPS that uses a 12 volt battery, and hook up the car battery to replace the original battery. The car battery will take like ten times longer to charge but would last ten times longer, plus you can charge it with your charger. I like the UPS idea. Try Flea-bay for one with a dead battery, and ask the seller the voltage of the original battery.

 

[Thegonagle]

I don't like the hydrogen-sulfide part of my idea.

 

[ZapZilla]

Does just thinking about it make one an Idiot or do you actually have to build one to be one?

I was looking for a solution to run my comp on battery power for up to 90 minutes or so (the approximate time of the rolling power outages), not just for graceful shutdown upon power loss.

[Cold shudder]Now what am I going do without my computer if/when the power goes out?[/Cold Shudder]

 

[Sluggo]

Are you really thinking that a fully charged car battery in your house is a good idea? There is nowhere to ground it properly, there are plenty of static electricity sparks around your house, bad fumes (kinds you can smell and otherwise.) I am guessing you have never witnessed a car battery explode, one of the scariest things you will ever see.

If you do choose to do it, will you list me as a beneficiary on your life insurance?

And of course there is always that nasty lead issue.

 

[ZapZilla]

What if I used Garfang's idea (old UPS with car battery) with the car battery/charger kept outside with only wires running inside?

 

[MissingLinc]

Unfortunately, if you have to ask, you probably do not have the knowledge to do it. You will need a whole lot more than a transformer (a big expensive one at that). You will need some other expensive stuff too and a lot of other parts. You are far better off just buying a good UPS. I recommend at least an APC BackUPS Pro as it is a really well-engineered UPS. The BackUPS Pro (unlike the regular BackUPS and almost all other generic home/office UPS's) has a true line conditioner with big inductors and capacitors, etc, along with the battery. A line conditioner actually boosts voltage during brownouts (to a point) and bucks voltage when there is a surge. They keep you in the nominal voltage range and filter RFI and other transients MUCH better than ANY "surge protector" (anything under $50). The regular UPS's have just a battery and regular "surge protection" and the input voltage (from your wall outlet) has to swing pretty far before going to battery (usually as low as 87-88V and as high as 140-145V) and your computer power supply and monitor (and anything else) will take the beating. Regardless of what ANYONE says, the inevitable voltage swings are the number one reason why unprotected computer power supplies and monitors eventually fail.

I even put my entertainment system on an APC 1250VA line conditoner (Line-R 1250 -not an UPS). One day, while playing on my Dreamcast, the power flickered on and off for ten seconds. My TV, stereo, sub, and DC never faltered and I did not lose my game.

Nearly all home/office UPS's, including APC BackUPS Pro's put out a stepped sine wave (not perfectly round) which is okay for power supplies but hell on AC motors. You have to step up to the professional level to get true sinewave output... such as APC SmartUPS or other equivalent.

I have been using APC products for almost ten years (at home and the office) and I do not believe anyone compares in quality. They are a little more expensive but they have a greater product line, more solid guarantee, and responsive customer service.

 

[Zoson]

Car battieries are deep-cycle, they need to be charged while they are being depleted or they will go dead. You can do something like this by setting up the car battery in parallel to a surge supressor. and hook up another surge supressor to the battery to regulate the current.
Click here for a diagram I drew
I don't endorse my method with any kind of warranty, it's your fault if you f*ck it up, but in theory this should work. To avoid the acid leaking, get a gel based battery (the new ones). They will not leak, or produce any gas.
EDIT: Oh yeah, you'll need an AC to DC converter to go between the wall socket and the battery (between the first branch and the battery) and you'll need a DC to AC converter between the battery and the second surge supressor (between the battery and the second branch)
-Zoson
P.S. It feels good to be back

 

[Thegonagle]

Well,

If I were going to try my idea, I?d keep the car battery outdoors, now that I think about it. You would only need to use a separate charger for a few hours after the blackout, not all the time; the charging circuitry of the UPS would most likely keep a full charge on. I also would not charge the battery while the computer was on (and hooked up through the UPS.)

 

[MissingLinc]

Between the dog and my computer, I took a while to type that and just read some more comments...

A SmartUPS XL will give awesome extended run time. My monitor and 300W CPU, cable modem and router/switch, and an external drive present less than 40% load on my SmartUPS700XL and will run at least 90 minutes.

See APCC.com for more info.

 

[ZapZilla]

MissingLinc Thanks for the vote of confidence and for your information

 

[Zoson]

ZapZilla, if you read my above post, read it again, I added an edit... very important or u'll blow up ur 2nd surge strip every time.
-Zoson

 

[etech]

Buy a good UPS, if you need extended time buy a larger UPS or get one that accepts additional battery packs.

You do not want a car battery in the house, they produce hydrogen gas when charging and can explode. Plus the sulferic acid inside does very nasty things to electronics and it will get out to some extent.

If you put it outside you have to worry about voltage line drops, running a power cord inside, not really worth it.

Car batteriers are not deep cycle, batteries for trolling motors etc. are deep cycle, made to discharge and accept charges with out damage.

Zosom, You didn't show the inverter but you cannot hook up the output of an inverter in parallel with the outlet of a wall socket, bad things will happen.

If you had to have something like this, get a trickle type charger and plug it into the wall and connect to the battery full time. Make sure the charger can supply enough current for full load(should not be a problem) Connect the battery to the inverter and connect the computer to the inverter. The battery will act as a very good surge supressor.

A charger will not supply more voltage then the cars alternator when running (14.6v I think) The invertor will be built to handle that voltage.

 

[Thegonagle]

Zoson,

No offence, but I don?t know exactly what you mean in your drawing, but it looks like the battery would surely blow up! A surge suppressor doesn?t regulate the current.

Please don?t do that. I don?t have PSP right now so I can?t post a drawing of what I would do.

MissingLinc has the best idea, which is a fresh, new out of the box extra high capacity UPS. My UPS idea was essentially to retrofit an old UPS with a extra high capacity battery. The gel style battery would definitely be a good idea to start with, but do not try to hook the battery up to the house current, except via the charger.

 

[ZapZilla]

Wow, lots of great information, thanks!

After looking at this APC link and considering my system:

300W power supply
PIII 800@1038 + 0.15A fan
1 hard disk
50x CDROM
21" NEC MultiSync6FG (Manufactured Jan, 1992)

I am wondering what my current draw is in order to estimate backup times. Their runtime calculator uses xxVA / xxWatts?

 

[d33pt]

Bah, if you already have the battery and charger, this is a piece of cake. Go to Costco and pick up the 300w statpower inverter for $35 bucks. Hardwire this to the battery. Depending on your battery's reserve time..this should be good to keep your computer and maybe a small monitor up for at least an hour..maybe up to two, depending on your setup. Not if you have peltier and water pumps and a 19" monitor, but for a basic PC this will do nicely. I have that inverter in my car running a computer and I can leave my engine off with the music playing for about 2 hrs before it dies, but I have an Optima car battery. good luck. lemme know if you need me to clarify anything. pretty simply stuff..dont worry about blowing anything up. BUT if you do...dont blame me =]

 

[d33pt]

btw..i just looked at Zosom's diagram and explanation...dont follow that..i think he's smoking crack or something.

 

[Windogg]

Trust me on NOT making your own UPS. I work the company that make most of the components (mosfets, micro controllers, capacitors, inductors, etc.) for APC and I've talked with the engineers. You do not want to be around when an improperly made unit fails. UPSes are also built to resist catastropic failure. We once had one unit come into our lab that "died" in fact everything was ok expect the battery pack. The system decided that even using it for "surge only" would be a danger. The battery pack is specially made to resist bursting but it had expanded due to improper care and age that we needed to use a Dremal and tinsnips to get it out.

I doubt yourt system will challenge a decent UPS. We tested a APC SmartUPS 620 and it ran for 30 minutes with a 17" monitor. One can be had for about $300 shipped. The UPS also comes with $25,000 insurance against an damage suffered due to the equipment not meeting it's stated specs. Not to shabby.

Windogg

 

[Soybomb]

Hmmmmmm problems in this thread so far:

car batteries are NOT deep-cycle batteries, they are not meant to be drained and charged constantly, they are made to get some use and then charged back up.

Now I'll admit I'm not quite an electrical engineer, but if you build something like zosan pictured......wear a good mask and some long sleeve clothes, having a shower nearby would also be recommend since its going to get nasty. In short, just go buy a UPS

 

[d33pt]

you can get deepcycle car batteries..mine is..

 

[Soybomb]

Fair enough, you can get deep cycle car batteries, but I'm betting that 95% of all cars out there don't have them.

I plan on putting another battery in my jeep along with a winch and it will be a deep cycle, but most people wont have them

 

[ZapZilla]

Windogg Your estimation of 30 minutes for the 650 equates to
200 VA / 130 Watts in their load runtime calculator.

Based upon that the 700 gets 43 minutes ($400)

and the 700XL 136 minutes ($580).

Thus, the 700XL appears to be the most bang for the buck for my needs.

Now, I'll just have to sit out an upgrade cycle to pay for it, but from what has been said, it'll be worth it.

Thanks to all for the info and advice.

 

[Zoson]

damn, i don't know what the heck is wrong with you guys, but i'm a freakin' EE student at columbia university i don't know what kind of credentials you guys have. and i added notes as to where the converters need to go to regulate the power supply. in short, you need to hook up the battery and the first surge protector in parallel so they get the same voltage and the same current will go through each. this way the current would then be recombined at the second junction and provide full current to the second surge protector where your computer is plugged in. if there is a loss of power, the battery will continue to provide energy because it will effectively become a series circuit. you may need a diode between the first junction and the first surge protector to prevent a short circuit when power fails.
-Zoson

 

[Soybomb]

Perhaps I'm being dense then zoson but when the power is on and going through your convertor you're shoving juice into the batter it looks like to me? How are you going to know at what rate to charge and when to stop charging?