AC Power ---> Battery

[Eric650]

I am building a custom, very small computer for my car. It needs to be as small as possible, but what is holding me back is the power supply. Ideally, I want the computer to run off of internal batteries. NOT the car batteries. In other words, runs off an internal battery like a laptop does. If I cannot get rid of the power supply I'll just get a power inverter and hook it up to my car's power jack.

I REALLY want it to be battery powered so that it is fully wireless. Unfortunately, as size is a huge concern, I can't have any large objects to make it work. My questions are these:

1) Can a battery replace a power supply? Or would I need both?
2) If I don't need the power supply, how can I hook up a battery to the power port on the motherboard? Is there a place to buy adapters for this purpose or something similar?

Any help is greatly appreciated. For those that are curious, I'm building a small yet full fledged PC to fit into the car stereo slot. Its about 7 inches wide and 7.5 inches deep and about 2 inches high. Battery doesnt need to fit inside but the power supply presents a problem as for my purposes the power supply would have to be enclosed. I intend to also be able to take out the PC from my car and bring it anywhere. I will use an inexpensive 15" flat panel monitor for the display. A keyboard with a built in mini-trackball should suffice since it wont be a touch screen.

-Eric

 

[Superdoopercooper]

Think of it this way: a power supply generally (in the case of your home PC) takes AC and converts it to DC.

So, if you're powering a computer... all you *REALLY* need is DC. So, you punt the AC/DC power supply and just use DC. The problem is, if you're building something like a home PC, you will need to provide 12V, 5V, and all the other voltages that a normal PS does. This can all be accomplished via a single set of batteries... you'll just need various regulators and stuff.

If you are doing a laptop kind of thing... well... I know with those, you throw in a 14V (or close) battery, and all the power is stepped-down inside.

So, I would recommend maybe getting some hi-capacity NiMH 'C' or 'D' Cells. The C cellls have 3800mAh and the D cells up to 7000mAh, which is a TON for D cell. Downside... COST COST COST. Even AA's are reaching 1800mAh, and those aren't nearly as cost prohibitieve. So, it all depends on your power draw and how long you wnat to be able to run,

If your 'puter draws 2.0 Amps, and you want to be able to run for 1 hour, then you'll need ~2000mAh. If you want to run for 2hrs, then you'll need 4000mAh. If the computer draws 5A, then even at the C cell power, you'll get only about 45minus of run-time.

There are many different games you can play... it's just wnat you want to do. I would suggests a small battery that just is used in the event the 'puter isn't plugged into the car's 12V. The power inverter idea is just so wacky since you are going from DC -> AC -> DC again. Almost makes more sense to stay in DC realm.

IF you need all the standard voltages, then I think that is 12V, 5V, 3.3V and some negative thing. Not sure. But if you put 10 cells in series, you have 12V there (or you could even get a small sealed gel lead-acid battery... for about $20, it has 7000mAh. I have one at home for other purposes... but it is great... a bit heavy - 5lbs? - for what you want, but cheap). Then, you get a run-o-the-mill Linear Tech or equiv. regulator to step down to 5V. Another to step to 3.3V, etc. You get the picture. The tough part wiill be if you need some whacky current draw, but only you'll be able to tell me that.

 

[Superdoopercooper]

Ok... forgot about the monitor. Do those things have a big power pack that you plug in. I've only ever saw the monitor part sitting on the desk.. .not what is actually plugged into the wall. If the FP runs off DC, then you can do the same thing there... if it runs off of 120V and has some transformer inside or something... then you'll either have to open it up and bypass the transformer with your DC batteries, or you'll just have to go with the power inverter trick.

 

[Eric650]

K thanks for the help....I havent bought anything yet, just doing research. I'm not sure about the LCD monitor either. I can ask a friend about that. I am going to use the mini-ITX motherboard from VIA that should come out pretty soon. It has a standard power connecter on the motherboard so I'm wondering how I can hook up a battery to that since it distributes the power properly to all the pieces. I haven't checked but Im assuming different voltages run on different wires that plug in to the motherboard. So If I can hook it up to different batteries with the right voltage, and plug each wire in the right port, I'm good to go. I am pretty sure the power supply which I dont want to use is 50W, which is very little. Or am I missing something here?