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    herbertmania's Avatar
    herbertmania Posts: 1, Reputation: 1
    New Member

    Oct 31, 2014, 01:02 AM
    DC to DC
    Wow this forum is cool.

    I am wanting to power my computer directly from a 12 volt battery bank.

    My computer uses a 12 volt 4 amp AC to DC adaptor.

    Can anyone tell me what I need to do so I don't destroy my computer.

    Do I need to use some kind of DC to DC voltage regulator? Do I need to have some kind of current limiter so I don't blow out the computer?

    ebaines's Avatar
    ebaines Posts: 12,132, Reputation: 1307

    Oct 31, 2014, 02:10 PM
    No need for any sort of voltage converter - 12 volts is 12 volts. I assume you will be using a pretty heavy duty battery. like an automobile battery. It may be prudent to splice a fuse into the line, in case of a short. Be sure to correctly connect the polarity on the plug that you are connecting to the battery - it's vital you not get it backwards.
    InfoJunkie4Life's Avatar
    InfoJunkie4Life Posts: 1,410, Reputation: 81
    Ultra Member

    Nov 18, 2014, 06:19 PM
    I would also suggest using appropriate connectors and thick enough wire for the system. For 3 or 4 feet 20AWG wire is sufficient anything over 10 feet I would recommend dropping to a 17 or 18AWG. The resistance created by a bad connection or too thin a wire can cause the computer to operate strangely or even try to draw more current, damage is unlikely, but still it may be undesirable.
    Appzalien's Avatar
    Appzalien Posts: 540, Reputation: 57
    Senior Member

    Nov 24, 2014, 10:18 PM
    Forget the car battery. At an average of 60 Amps it would fry your system. Just think of the size of the cables on that sucker. If you tried using power supply jack wire it would melt from all that current. Something like two 6 volt lantern batteries in series would be safer but would not last very long. Four of them would be better two sets of two in series then hook the two series sets in parallel but it wouldn't be very portable.
    ebaines's Avatar
    ebaines Posts: 12,132, Reputation: 1307

    Nov 25, 2014, 06:50 AM
    Appzalien - sorry mate, but you are absolutey incorrect. 12 volts is 12 volts. It doesn't matter how much current the source can provide - it will not "fry" the PC. Using a car battery would simply allow the PC to run longer befre the battery drains down than using a lattern battery. The specs the OP provided implies that the PC draws up to 48 watts, and a lattern battery would never be able to do that.
    catonsville's Avatar
    catonsville Posts: 894, Reputation: 91
    Senior Member

    Nov 25, 2014, 04:46 PM
    I agree with Ebaines. A car battery is capable of handling up to 60 amps, does not mean that anything connected to that battery will have the full 60 amps injected into what ever is connected to. If 12 volts is needed and 1 amp is required, only the 1 amp will be taken out of the battery. Good idea to fuse though.
    cdad's Avatar
    cdad Posts: 12,701, Reputation: 1438
    Internet Research Expert

    Nov 26, 2014, 03:54 PM
    You dont really want to use a 12v battery as a powersupply for a computer. You run the risk of way too many problems. If you hook directly to a battery you actually have a variable source not a steady 12v. All batteries cycle through a power range per cell. So in theory you might be starting off with 13.2 to 13.5 volts and end up somewhere around 11 volts. It may not sound like a lot but that is enough to vary your harddrive speed and cause it to write corrupt sectors.

    If you absolutly need to run off of battery consider a good UPS or buy a laptop.
    InfoJunkie4Life's Avatar
    InfoJunkie4Life Posts: 1,410, Reputation: 81
    Ultra Member

    Nov 29, 2014, 07:45 AM
    Modern computers generally have switching power regulators within the motherboard to prevent overvoltage and undervoltage to individual components. The battery may have a hi/low cycle as you described, but most computers are fault tolerant.

    A switching regulator will generally draw a little extra amperage to compensate for a voltage drop. Even the regulated power supplies provided with most laptops show some ripple on the oscilloscope. Throughout the life of the power supply voltages will vary as much as 20% on some machines, and the computer will still be fully functional.

    A computer that does not fair well with battery supplied power may want to try a DC to DC Switching Regulator, which will more appropriately level off the voltage rises and drops associated with a battery. It's a bit more heavy duty than those within the laptop itself.

    My biggest concern in this process would be the type of power supply originally used with the computer. Some power supplies have a pulse code or variable core voltage to prevent non-OEM devices being used with the computer. This would be much more difficult to overcome from a project standpoint. You would have to experiment to find out.

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