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how to battery power a desktop pc? Answered

I basically want to convert a desktop into a notebook. It won't have a 90W+ under load.
I've done it all except for the power source. How can I power things like in a notebook using ni-mh or li-on batteries?
I must be able to monitor battery capacity just like a notebook too.
I've searched a lot and I'm confused.


What are the specs of the PC?

that really doesn't matter as I'll change components often. I've all things sorted appart from the PSU. But it won't consume more than 90W in full load that's for sure.

Can't really understand how to power this like a notebook. Should I use a picopsu plus a picopsu ups? should I get an openups? but that's so expensive.

how about using a modded external notebook battery?
how to monitor battery status in windows and linux?
I've seen many solutions but they are all for sealed lead acid and that's a no go. I want to get ni-mh or li-ion or lifepo4.

Pick your battery, make a good solid 12V, 5V and 3.3V regulator circuit and your set. But they have to be very good and stable regulators. I would suggest pulling apart an existing PSU. Isolate the AC side from the DC side. You'll have all the regulators and protection needed there. Double check how much DC voltage the PSU has coming from it's bridge rectifiers and then connect a battery with the same voltage. As for monitoring you'll have to trick the system into thinking it's on battery power so the OS can monitor the power for you. But there are plenty of free applications that will monitor voltages for you.

How would you make a 12V, 5V or 3.3V regulator? Which one would be allocated for what resource? And where would you conne battery. You could not run the battery to the standard AC cable because you would not be able to pass any current through the PSU so could you discard and components native to a new PSU(Presumably what Portions of a standard desktop PC need AC current?) Are you suggesting that any motherboards larger than a mini-atx draw AC, or are your just rather imposing the suggestion that a mini-atx mobo would work best here? What are bridge rectifiers, are these before the power output after the source?

Your not going to make a decent one on your own with off the shelf parts. Power supply design gets tricky. It's much easier and cheaper to get a DC o DC PSU. Google is your friend here.

No PC uses any kind of AC power. Go and google ATX power connector pinout and see what voltages go where. Sounds like you know little to nothing about electronics. Start doing some research. There is a lot for you to learn.

You wouldn't plug the battery into the AC cnnector. you would open up the supply. Find the voltage regulators in the supply and connect the battery to the input pins on those regulators. You will find 1 or more 12V regulators, a 5V regulator and a 3.3V regulator int he supply. You would not connect the battery to the 12V regulator. Just plug it right into the output of the regulator. But all of that is a bit over your head at this point.

Bridge Rectifier takes AC and converts it to DC. So 120VAC in will be a little less than 120VDC out. Nothing is 100% efficient so there will be some power lost as heat. Typically the AC power goes into the PSU, through transformers that bring that 120VAC down to say 15VAC. That 15VAC goes to the rectifier to become 15VDC and then off to the regulators which take that 15VDC input and put out either 12VDC, 5VDC, or 3.3VDC depending on the regulator. There is all sorts of other components in there used to help clean up the power and make sure it stays nice and steady and protects the PSU and PC form getting too much current or voltage.

When this question was originally asked mini-itx motherboards where primarily used to fit in small spaces and use vary little power. That isn't the case anymore. Now days you can find gamer lvl boards in that form factor.

Isn't there any easier way using off the shelf components? I don't feel comfortable messing around a lot with psu cables.
and how could I trick the system?

Not knowing your specs and future needs it's hard to recommend a solution. A 120W Pico PSU may or may not work for you. If your motherboard is a typical tower motherboard then it will need a 12V CPU connector which the Pico doesn't offer. It's designed for a mini ITX solution utilizing a mobile processor. But any 12V source will power it.


Just gotta be sure to get a large enough battery to run your system. If you max the system out at 90W that's 7.5A to 8A being drawn from the battery. So it will require a fairly large battery to run longer than 45 minutes. You'll still need a separate charger for the system. Not sure you could get the system to monitor the battery through the OS.

There are no off the shelf options to convert a full PC to a laptop. If you want to do a DIY notebook you'll want to start with a mini-ITX motherboard. But your end result will be a rather bulky unit.

thanks for the help. As for the specs they'll vary. I doubt it will make any difference if I use 4 or 16gb of ram or a 512ssd or an hdd.
But yes I'll be using a mini itx. Also picopsu's can power mini itx motherboards with desktop cpu's with no issues. I've used it many times in several builds without problems.

the link you provided doesn't work.

having a fairly large battery isn't a problem neither being bulky. That's not why I asked help.

All the help I need is to power the motherboard with batteries and to monitor the capacity. simple as that. nothing more. I've seen some solutions but they are all related to lead acid batteries so it's a no go for me.

would this work?


That would cover your needs. It's just a DC to DC converter. Give it 12V or more and it will run your PC. Doesn't matter if it's a strong 12V wall adapter or a 12V battery. You'll still need a separate charge controller to charge your battery with.

Wow those are excellent options. Though the first one is looking for AU not Dollars even though the picture shows a US plug. The second one has a lot more juice in it so it will last longer for you.

To monitor the battery i'd try to install the battery so the on board LEDs can be seen easily. Or open it up, desolder the LEDs and put them on wires so you can place them in a good position to be seen.

What you need is a APC UPS circuit board, a data cable 940-1524D, 20amp battery terminal cables and a battery as per your need (at least 7 - 9 ah). Links below :



This may not fit inside the CPU tower itself so you may need additional housing too.

I forgot to mention it, but, there exist forums like,


that are pretty much all about building your own car-computer.

So it may be the case that someone has already built a computer very similar to what you want to build, and ?maybe? also he or she already explained in detail how this was accomplished.

I've already read the forum
that doesn't work for me because:
1) they allways do things with lead acid
2) they don't monitor battery capacity
3) they don't charge a built in battery

It just doesn't help me in any way. In fact I've already built a car pc myself and didn't had any issue. the psu connected directly to 2 cables to the battery and to the motherboard and that was it.

That's not what I'm trying to do here.

I'm trying to transform a desktop into a notebook. Built a battery pack to connect to the motherboard and to charge it. Basically building a notebook from scratch.

I would favor lead-acid ("deep cycle") because it is less tricky to charge and more economical. Li-ion is great for portable power with greater power:weight ratio, but you do not need that! Look for a big fat 12-volt gel cell and if you want to carry it, get a piece of luggage with wheels. Your idea is good if you can avoid the invertor+PSU because that is two layers of inefficiency. Your project will be cool due to its monstrosity nature. Otherwise, don't fight it and just get a notebook!

If you want a battery that is like a laptop battery, I think the easiest way to do this would be to look at what they call, a "external laptop battery".


It is basically a laptop battery, but without the laptop. Typically it comes with some sort of built in fuel gauge like battery monitor, plus an AC adapter to charge it with.

If you were going to find a battery like this, the next trick would be to find one matched to the input power (voltage and current) requirements of of your display, and your computer power supply.

For example, I can sort of imagine an external laptop battery that provides 16 VDC, plus a display that wants 16 VDC (or maybe 15V, but 16V is close enough), plus a DC-to-DC power supply that was intended for a car battery, nominally 12V, but totally comfortable running with its input at 16V.

By the way, you sort of have to sort of read the specifications of the DC-to-DC supply to find out exactly what is the range of input supply range voltage it can handle. Typically there is some range of input voltages, e.g from 9V to 18V, or whatever it is. Actually I got that number from one of the PSUs on this page,


I linked to previously.

Anyway, the point is if you can provide all your components (eg, computer PSU, display, audio amplifier) with voltage and current that they're happy with, and then everything will be running and happy... as long as the battery lasts.

By the way, I get the impression you don't like lead in your batteries. If you don't like lithium either, I think the next thing (in energy storage chemistry) is maybe, uh, hydrogen.


I mean the specs look good, but I can't tell if they're actually selling it because the "buy it now" button seems to link to nowhere, and God only knows what it costs!


There exist computer power supplies designed to take 12 volts DC as input power.

Typically the market for these things is for people who want to install computers in their car, or boat, solar powered shack, etc.

A Google(r) search using the words, "12v dc atx power",


returns a bunch of links to various hardware-mongers selling these things.




It is also possible to power your desktop's AC power supply, using AC power provided by an inverter, powered by batteries. That might be the cheapest way to do things. However, an actual DC-DC supply, one intended for powering a computer, will give you better power conversion efficiency, and also less electrical noise of the 60 and 120 Hz variety.

I was wondering if there was a resolution to this. I was thinking of converting a 23" all in one desktop into a laptop, but am unsure how to tell what size battery would be necessary to get laptop like performance. The weight/dimensions don't matter much, but I looked at some car jump starters and the large ones seem to be too cube shaped to be used. How long would something like this http://www.amazon.com/BESTEK%C2%AE-Inverter-Outlets-Charging-Cigarette/dp/B00UFERZKO/ref=sr_1_14?s=automotive&ie=UTF8&qid=1446405064&sr=1-14 power a desktop like an HP Smart Touch 23"

I am trying to think how to answer this question without having to explain everything about everything.

I will start with the power converter you link to here,

This item is sort of a typical 12-volt power inverter. It takes, as its input, direct current (DC), at voltage of approximately 12 volts, like a car's battery can supply. In fact, this gizmo is pretty much intended to work with a car's electrical system. The idea is you can use this gizmo to convert "car supplied electricity" into something resembling "mains supplied electricity", with which you are probably somewhat familiar,

I cannot tell you how long, how much time, measured in seconds or hours, the 12-volt inverter, can power your computer. The answer to that question will be, approximately, the quotient of two numbers.

One of these numbers is the time rate at which your computer consumes energy, measured in units of joules per second, or watts, or watt*hours per hour. Call this number P.

The other number is the energy storage capacity of the battery, measured in joules, watt*hours, or volt*ampere*hours, or something like this. Call this number U.

Dividing U by P, gives T=U/P, and that is your estimate for the amount of time, the battery will last. This explanation of battery life, how battery life works, is overly general, overly simplified, and I did not even bother to mention the fundamental equation for electrical power, P=I*V.(I is current. V is potential.) I can provide you with specific examples, if you want them, but the reason I explain this only briefly, is I am intentionally avoiding explaining everything about everything.

Regarding the inverter you linked to at Amazon(r) there, it does not come with a battery, or a car with a battery. They are expecting you to provide that part. It would be kind of amazing if this deal included a free car! Although, you'd have to wonder about the quality of the included free car...

By the way, this 12-volt inverter gizmo, is kind of ubiquitous piece of hardware. I mean maybe not as common as a shirt, or a toothbrush, or a wristwatch, but I dunno. You might want to check your closet, or attic, to make sure you don't already have one.

Even if you don't have one, if you have even a small number of friends, I am guessing it is ?likely? you know someone willing to let you borrow one.

The reason why I suggest borrowing an inverter, and maybe also borrowing a car to plug it into, for to test it out with your computer, is the last time I actually tried running a personal computer from a 12-volt inverter, there was this awful 60 hertz, 120 hertz, buzzing noise on top of the sound card signals.

In my reply from like a year ago, I briefly mentioned this noise problem, but I failed to mention how loud, how annoying, how this basically ruined any tasks for this computer involving sound (e.g. playing music or videos).

Anyway, that's the reason why I recommend trying this setup, powering a PC via 12-volt inverter, first with inverter you already have, or a borrowed one, because the audio noise might be unbearable.

I think the preferable option is a computer power supply, made for, designed, to run from a 12 volt DC supply. These exist, but are a little harder to find, and probably more expensive, than the usual, ubiquitous, mains powered computer power supply. The places I linked to, like a year ago, that's not an exhaustive list. You'll find other sellers, if you search for them.