Laptop power supply.

Discussion in 'General Electronics Chat' started by kiyoukan, Jul 24, 2010.

  1. kiyoukan

    Thread Starter Member

    Nov 17, 2009
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    I have have a dell inspiron 1150 and over the many many years of owning it i had a problem of the barrel jack coming of the board.
    It seemed at least once a year i had to take it apart on solder it back on.
    Well today it would not take. I think that part of the board is now dead. i could try the whole take the green film of and make the contacts larger but i want to find a permanent solution.
    What i want to do is to hard wire the connector into the battery terminal.
    The battery is a Li-ion batter 14.8v at 6450mAH with a 96WH capacity.
    And the Power supply brick is19.5V at 4.62A
    I have never done anything like this before and wanted some advice.
    I would like to have the battery in there still so i can still use it as a portable computer but if it will interfere with it i dont mind not having it.
    I was thinking i would have to drop the V down maybe using a voltage divider circuit or something but i decided it might be better to get people with more knowledge before i risk my laptop.
    Thanks so much for any help or advice.
     
  2. tom66

    Senior Member

    May 9, 2009
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    Do NOT do this. The laptop has a charging circuit to prevent damaging the battery. Every cell has to be individually charged. Failure of the battery, often catastrophic (i.e. fire, explosion, smoke, damage to laptop/battery/surroundings), will result, if you overcharge even a single cell.

    http://www.youtube.com/watch?v=QJCZ4ayioCU
     
  3. kiyoukan

    Thread Starter Member

    Nov 17, 2009
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    Yes i figured that would be a problem that is why i stated i do not care if i dont have a battery that works i just need it to work.
    So if i scrap the battery and want to use the psu in its place how might one go about doing that?
    So to make things clear i dont want to charge the battery i just want a place to connect the leads of my psu so this thing will work.
     
  4. tom66

    Senior Member

    May 9, 2009
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    Just solder the terminals for the DC power supply to the nearest component connected to the jack. This will most likely be a capacitor or diode. You will have to run some relatively thick wire, because the power supply can deliver 4 or 5 amps.

    Connecting it to the battery terminals will damage the laptop, because those terminals are designed to accept a 14 volt input not a 19 volt input. There will be a switch mode converter which probably converts either the 19 volts down to 14 volts or the 14 volts up to 19 volts. Either way, damage could result from too high a voltage present across the battery terminals. I wouldn't be surprised if Dell have omitted any protection against this because they do not expect it.
     
  5. kiyoukan

    Thread Starter Member

    Nov 17, 2009
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    Also the issue i have is the psu i have has 3 terminal in it. outside barrel is negative inside barrel positive and then a center pin is something else no idea what.
    Due to the years of soldering it is now hard to trace the leads around the board in that area as this has been soldered around 15+ times.
    Also i am not sure but i think i let the smoke out of the board in that area, i cant be sure but some smoke was there that was not my irons.
    I put in a charged battery and everything worked so i think i killed the charging circuit for good.
    I would not be going this route if i had not tried every other option.
    So if i drop the voltage on the psu down to 14.8 will that be all that i have to do?
    There will be no battery in there once this mod is done.
    So i wont have to worry about over charging anything.
     
  6. tom66

    Senior Member

    May 9, 2009
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    I can tell you the center pin carries data which identifies the laptop charger as a genuine Dell.

    However (this is a bit of a rant), it's poorly designed because what you essentially have is a four or five foot antenna connected to the output of a microcontroller. This picks up ANYTHING static electricity wise, and can often fry the chip after a while. I think Dell has fixed this in the newer chargers, but the purpose of this wire is only to ensure Dell has revenue from selling chargers, in my opinion, as they are quite common to fail (I've gone through two or three... luckily covered under warranty.) However, the Data wire only stops the laptop charging the battery if it is not present. The laptop will still run off AC without the Data wire, but it will warn that you are using a non-genuine charger.

    No, connecting even a reduced voltage to the battery terminals will not work because the battery normally communicates with the laptop and the laptop will most likely think the battery is always flat and refuse to boot. It would also force whatever OS you are using to register the battery as always critical. It could also damage the laptop because the battery mode may be designed to deliver less current, but I'm not sure.

    A voltage divider would not work it would cause the voltage to vary. Since you are talking about 3-5 amps you will probably need a switch mode converter, a linear regulator might work but will get very hot.
     
  7. kiyoukan

    Thread Starter Member

    Nov 17, 2009
    63
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    So if i did fry the power terminal there is no way to make a "Fake" psu battery?
    I was thinking of opening up the old battery to remove the battery's and seeing if there my only other option is to buy a new 100$ mother board.
    or to just charge the battery from another laptop and then only use this thing for the 35min the batter lasted anyway. I was hoping to be able to turn this thing into a more of compact desktop.
    As that is what i mainly use it for. it sits on my work bench with schematics on the screen.
    Well seeing as the laptop is dead now what are the chances that i can do something? Can i make my own charging psu for this?
    i can use micro controllers.
    I am looking for a fix to turn this thing into a compact desktop, if i had to build a circuit to fool the laptop into thinking it was full would that be that hard?
     
  8. tom66

    Senior Member

    May 9, 2009
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    The problem is, it's digital IO. You would have to figure out the protocol the battery uses. There's usually a battery IC in one of them, which identifies the battery and provides charging statistics. This way, the laptop knows that the battery will charge in 30 minutes or whatever, or that it has 35 minutes of life. Without this information, it is possible the system will not even register the battery and refuse to boot; if it does, the battery will always show up as completely empty.

    Can you post a picture of how damaged the connector pads are? Make sure you include some of the surrounding PCB. We're interested in the top and bottom of the PCB, so take pictures of both.
     
  9. kiyoukan

    Thread Starter Member

    Nov 17, 2009
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    I do not have a good camera the best i have is a web cam but the connectors are salvageable if i take off the green film and just use a different point the problem is that i fried a chip on the board. a small puff of smoke came out of an ic so i think i kinda left myself without a lot of options. but the laptop works with a battery still so that was the only good part.
    So if i open up the battery cant i just use whats in there to give off a fake status reading?
    After removing the cells of course.
    I have no problem destroying a perfectly fine battery if it means getting this up and running.
     
  10. tom66

    Senior Member

    May 9, 2009
    2,613
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    Aw, crap... That sucks. Can you still read the part number? Once you let out the magic blue smoke, you can't put it back in, but you can replace the part. How'd you fry it anyway?

    Regarding replacing the cells in the battery with a voltage source. It *might* be possible. I guess the first step would be to build a 14.8V @ 5A power supply. You could power the secondary supply from the 19V power supply, but that might not be enough due to the lost heat in the secondary supply. You could also have a look at these aftermarket laptop power supplies. 15V is fine for a Li-ion battery, the voltage could actually go as high as 16.8V (4.2V per cell) though I wouldn't try this. The problem I could see with this is you'd need to trick the battery IC into reading the four 'cells' to get an accurate meter. I suggest a four element resistive divider made of 1k resistors, each going to the control board.
     
  11. kiyoukan

    Thread Starter Member

    Nov 17, 2009
    63
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    well i have a 16V at 4.5A psu that i could use.
    Its a bit under the power i want but i think it could do
    So i am going to open up the battery i for a long time have been a programmer and good at soldering so i am the guy that codes your chip so i am not all to familiar with terminology got any diagrams that i can read as i open the battery pack.
     
  12. tom66

    Senior Member

    May 9, 2009
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    Be extremely careful in opening the battery pack. Keep a fire extinguisher handy. I'm not kidding, these packs are like ticking time bombs. If you are poking around with your screwdriver and you slip and puncture a cell, they can explode.

    Make notes of the battery positions and where the wires go. You should really get a digital camera though I suppose a webcam would suffice.

    If the 16V power supply is a big brick (and is heavy to boot), it is probably not going to work because it is likely an unregulated AC->DC power supply, which means when there is not much load it can produce voltages of up to 20V causing damage if the laptop is shut down and it will have a quite large ripple which could cause the laptop to malfunction especially under high load conditions. You will really need a switch mode power supply. I don't know where you live, so I can't make any suggestions, though in the UK Maplin sells this supply:

    http://www.maplin.co.uk/Module.aspx?ModuleNo=220918

    It has a 15V and 16V output. I'm not sure if it can deliver enough power to your laptop. What's your current charger's rating?
     
  13. kiyoukan

    Thread Starter Member

    Nov 17, 2009
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  14. tom66

    Senior Member

    May 9, 2009
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    OK. I suppose I'll watch along, but I have to go to sleep soon. It's midnight here. It's a weekend and I'm bored, so I'll probably be up for a few hours.
     
  15. kiyoukan

    Thread Starter Member

    Nov 17, 2009
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    Okay well it was a no go but there was no smoke so hmmm.
     
  16. tom66

    Senior Member

    May 9, 2009
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    Hmm, well it probably has something to do with that yellow wire.
     
  17. hobbiest_2k3

    New Member

    Jun 12, 2009
    5
    1
    @ kiyoukan

    can you pls explain in simple words, what problem you have, is it with your battery, or with AC Adopter, or with ur Laptop.

    maybe i can help you
     
  18. kiyoukan

    Thread Starter Member

    Nov 17, 2009
    63
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    My laptop has a broken charging circuit.
    So to use the lap top i need to convert the battery terminals into new ac terminals.
    i ripped the batters out of the battery case so now i have the circuitry, the question is how do i wire in a dc psu instead of the battery's.
     
  19. tom66

    Senior Member

    May 9, 2009
    2,613
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    Show me what you did, I guess you should start the stream.
     
  20. kiyoukan

    Thread Starter Member

    Nov 17, 2009
    63
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    i am actually about to head out to microcenter but i will be back in about 1hr. and all i did is what was in the schematic.
    the first gray wire has 10v the second has 5v and the yellow is at ground.
     
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