The other day, my home had power-outage for like 6 hours. I could go buy a UPS (Uninterruptible Power Supply), or I can make my own UPS using a car battery.
Well, I am just hoping this DIY UPS lasts 6 hours so I can keep using my spare laptop, which shouldn’t need that much power anyways to run off the UPS. But if I tried to run my desktop PC, it’d probably last only 2-3 hours at most, maybe even less.
This DIY is for 220 Volts so you will have to make some calculations to make sure you are providing the correct number of invertors and etc…etc… Btw, if you do use it for powering up your laptop, you don’t need an invertor as most laptops are around 12VDC anyways, which is what car batteries are at. (But you will need to hack an adaptor to the laptop for sure)
In this article we look at how you can cobble together a 220 Volt power supply using components you can buy at your local automotive store. But first it is important to understand a few basics about batteries, and how to convert 12 Volt DC battery supplied electricity into 220 Volt AC current that your household appliances can use.
A twelve Volt battery is a storage device that, when charged, stores electricity in chemical structures that can reverse and release electricity if required. Batteries are typically rated in Amp Hours (AH) – ie how many Amps for how many hours the battery will perform. An inverter is a device which can take the DC current from a battery and convert it into 220V AC current for your appliances.
To calculate how many batteries you need, and how big an inverter is quite simple. Investigate the specification plates on the back of each appliance. In the case of my laptop, the power supply is a 90W unit.
For an inverter one can work on a rule of thumb that to produce 100W will require approximately 10 Amps, hence in reality the lap top requires about 10 AH of battery life per hour. With a 90 AH battery one can therefore expect about 9 hours of power before the battery provides too little current to keep the inverter going. But it is not this simple.
10 Responses to DIY HACK – How to make your own UPS for your computer and other peripherals during power outage!
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lol! Never thought auto battery can be used in that way. Cool idea, mb I’ll even try it for my external hadrdrive and monitor =).
Alas, your post came too late. I have invested in an inverter and a UPS at some cost and now find that I still cannot use my desk top. What the UPS does is to give me a warning that the inverter is not supplying enough juice so that I can save whatever work that I am doing and shut down till the regular power is switched off. I am told that the UPS needs to be modified to take the juice that the battery will supply. There are special units that can work but I was not told about it when I bought the gizmo. Now I understand that there are also special batteries that are made specially for inverters!
Oh yeah for sheezy, maybe I can find some UPS hacks…
Ummm, You can’t do this to a computer. Please let me tell you why before you find yourself suddenly damaging your computer and needing a new power supply (and causing damage to computers and power supplies of people who also try this).
The power supply of computers and especially laptop computers need the AC voltage to be a nice, clean sine-wave. Inverters produce a nasty, sharp square wave that would be fine to power up household appliances, but not computerized equipment. Household appliances would be coffee makers, blenders, analog clock, toaster, toaster oven, lamps, etc. These devices have just a heating filament or lighting filament, or a motor coil in them and can run on square-wave just fine. Computerized equipment are designed to run on sine-wave, not square-wave and include sensitive / advanced electronic devices such as computers and especially laptop computers, VCRs, DVDs, digital clocks, digital cameras, microwave ovens or other devices that generally have circuit boards with lots of transistors and chips in them. These can be damaged by square-wave voltage, static electricity, power sags, power surges, brown outs and even blackouts. This is why you buy either a surge protector strip (if you’re cheap) or better yet a UPS both of which provides a sine-wave from your battery. About 20 years ago I purchased a UPS and used it happily for 7 years until the battery wore out. I live in an area with a lot of spikes, sags, and outages too. But the UPS would faithfully clean them all up, that’s what it’s designed to do. One day the battery wore out and died. They don’t last forever. But I’m a cheapskate WHEN I CAN AFFORD IT. And instead of replacing the UPS I replaced the battery with one of 10X the Amp-hour rating. Then when we had power outage I could run the computer all night instead of an hour. That was cool. Recently, after twenty years of usage the UPS finally died, the battery is still good. Of course I replaced the UPS. It outlived 4 computer systems (the computers were replaced because they went obsolete) during its life and I am happy with it’s performance.
I’m not trying to pick at you or sound like a nay-sayer. I’m just concerned for you and your computer system. When you run a computer on an inverter you roll the dice on it’s life every time you power up. You said you were doing this to save some money. I know it will work for a while – if you’re lucky a long while. But it won’t save you any money if your stuff is damaged and you have to buy it all again. And since you are giving this info out to the world I’m just as concerned for everyone else as well.
Actually you can run computers on 12 volts DC fine, Google does this for their web servers to save money.
Hmmm… funnily enough computer power supplies (both desktop and laptop) are of the switching variety – that is, they chop up the power you supply them with into… wait, can you guess it….? nasty square waves! Even if your feed your computer the cleanest most pure sine wave AC, it still ends up as square waves! reason they do this is that transformers saturate at lower current levels with low frequencies than they do with high frequencies, so by using a switching circuit you can increase the rate at which your current alternates. Instead of needing a large transformer that weighs several kgs to do the voltage conversion at 50/60Hz (depending on where you are in the world), you can use a much smaller one to do it at several tens to hundreds of kHz. A nice little benefit of doing it this way is that the high frequency AC output from the switching circuit is then much easier to rectify then filter/regulate into stable, clean DC power than the same output at a lower frequency. Funnily enough, if you ran your actual computer (all those transformers and chips) from the most pure and clean sine wave AC power you’d probably f**k it up since they’re actually made to run from DC.
Which means I should probably also add…
It’s fine to run a computer from an inverter… just avoid anything cheap and nasty and you’ll be fine.
True, AC power is really not used for anything other than lamps and washing machines, everything is converted to DC power.
I use an inverter to power my laptop while in my car (not driving).
However the idea of using a car battery to power a DIY UPS for at home is appealing. I’ve found an article here: http://www.dansdata.com/diyups.htm – about rolling your own UPS.
I guess the main proviso is – you need to know what you’re doing. All of the components – battery, power supply, inverter – can interact with each other in strange and exciting (read – dangerous and expensive) ways. Batteries are particularly sensitive to the way they are charged and left on permanent charge. Leaving a “12V” car battery on constant charge (float charge, 12V but it might be more or less depending on the battery, read the article link I posted above) will trash the battery unless you give it a topping charge of 14.4V for a few hours every 6 months. Stuff like that. Stuff that isn’t in this “yeah just bang ’em together and off you go” article 🙂
The stuff about square waves and sine waves is also dealt with. Basically a modern inverter will provide a “modified square wave” which is good enough for most electronic equipment as your power supply for that piece of kit will just convert the modified square wave back to a DC current anyway.
Stupid question:
12V DC battery output => inverter => 240V AC current => cable => computer power supply => DC current in cable to laptop => laptop
Would it not be possible to do away with the inverter altogether and get a straight adapter to run from the 12V DC battery, through some sort of transformer, straight into the laptop? There must be a lot of power lost when the current is converted into AC and then back out again…
They make pure sine wave inverters. More expensive than square but are available. West Marine sold some years back for boaters on the water where large battery banks are the norm.