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Thread: you dont necessarily need a voltage regulated PSU

  1. #41
    FLAC
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    Of course! If you hook up the PC and battery to the *switched* 12V, then you are safe from over voltage (at least in my car since it switches off during the crank). However, you are forced to hibernate the pc (preferably automatically) at ignition off. But an additional plus is your PC can't drain your main battery!

    Overall, I think I vastly prefer this approach. I was going to go with hibernate anyway.

    And I read somewhere that some VIA systems only use 7mA in standby. So it would last a long time off just the 7.2*Ah battery (43 days!). So standby is potentially still viable.

    And no diodes are harmed (required) in the making of this solution.

    I like!

  2. #42
    FLAC
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    Quote Originally Posted by justICE
    True they can produce 14.4V when charged (or charging). Putting two diodes in front of the original posters PSU will cause a problem when the car is off. He would then have ~10.5V.
    Not true. These batteries output ~13.6V. Since the allowed range for the mini box psu's is 10.5 to 15.5 it will work fine.

  3. #43
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    1st post... long time browser

    I too would like to know about these "charging electrics". To my knowledge, the electrics that you use to plug your trailer into are the same circuits that your brake and indicating lights are connected to. No special "charging" circuit.

    And if the gel battery is indeed connected to both the alternator and the computer at the same time then, as others have said, surely the PSU will be getting whatever voltage the alternator is cranking out?

  4. #44
    FLAC
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    Yes it is. No it's not a problem. From mini box:
    Q) What is the voltage operating range of the PW-60/70?
    A) 10.5-15.5V. Below or above these voltages undervoltage/overvoltage protection will shut down the power. The boards cannot be damaged unless you apply more than 24V.
    Obviously other DC-DC power supplies might have different input requirements, so you would need to check.

  5. #45
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    Quote Originally Posted by Arathranar
    Not true. These batteries output ~13.6V. Since the allowed range for the mini box psu's is 10.5 to 15.5 it will work fine.
    First, when the batt is not charging (car off) 13.6V is optimistic at best when the car is off. My car batt supplies 12.5V when off. 2 diode drops later we are looking at 10.5 - 11.0V.

    Second, The range 10.5 to 15.5 is the safety shutdown range. When the mini box answer section states will "work" from 10.5 to 15.5V I assume he means the 5 and 3.3V rails can continue to supply 5 and 3.3V between these limits; however, the 12V is unregulated so the value of anything running off this rail will see 10.5-11V. Not sure if everything will work as intended with a reduction of 13-15% voltage decrease.

    Finally, The voltage supplied will decrease as the tank is discharged. 50% discharge will result in around 0.5V decrease. If your just running a little eden (4 amp draw or so) with a 7.5ah tank at a ~10% decrease in voltage because of the diode drop your looking at ~50 mins before the safety shutdown hits. Plus, you will be running at 10.5-11V, which opens up a whole new can of worms. p4 and amd mobiles will pull even more current.


    Get one of These =)

  6. #46
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    One of those (can't remember which - cycled I think though) had a max current limit - 0.2A I think it was. The other didn't. I'm intending to run a micro ATX m/b with an AMD2500+ so I expect my wattage to be high. So I'm going to get one of the 200W dc-dc psu's from mini-box. 200w/12V ~= 16A which is a lot of current (but nicely allows for a 15A fuse assuming I don't quite need the full 200W).
    Well darn now I just read this. Hey don't take my replies as an attack on you or a critique I am just trying to help you get your solution without heart-ache.

    Is that a mobile 2500+ or just the standard 2500 barton? I have the barton for my home computer and the processor alone uses a whopping 7.734 amps. Also, that power supply is rated for 13.5 V across the 12V rail. It may be something you will need to consider if you are running fullsize HD's, fans, CDrw video cards or anything else off the 12V rail.

    Also, I could not find a "safe" range for the 12V rail in the tech documents at amd (they assume everyone uses the standard atx ps) so I asked the tech support. I will post when they reply.

  7. #47
    FLAC
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    Ah. That all makes lots of sense. I'm not arguing you should put diodes in (I wouldn't) but I didn't think it was a bad idea. Looks like I was wrong.

    Ah, you've just opened my eyes. I was looking at the Morex 120W kit and intending to use a tank to do the voltage regulation. I thought that would be a cheap way to get a PSU + AC adapter (useful during building and testing of the system). But the Casetronics 120W kit associated with the above DC-DC regulator requires a Vin of 14V min and the Morex 120W kit doesn't actually say anywhere but looks to be pretty much the same setup. Doh!

    So that pretty much forces me to the point of using one of the mini-box 200W kits which are supposed to be P4 compatible and I may as well start buying the bits I need as I don't think there are any alternatives that will do what I want.

  8. #48
    FLAC
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    I wasn't - I actually like having my eyes opened when I'm wrong about something (as long as I'm not insulted at the same time ).

    Dang. 7.7A for just the cpu? Yes I've got the 2500 barton. Gulp. Is that 7.7A all on the 12V rail? That can't be correct - that's 90W for the cpu alone. I thought you only hit that for the really high end cpus from Intel and AMD?

    I was going to use the 2500+ and mATX m/b because I have it and have no better use for it. Saves $300-500 on a via solution. But if the power usage really is that high I might be SOL with a DC-DC solution.

  9. #49
    FLAC
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    Argh.
    >> AMD ATHLON XP 2500 MOBILE 1.8GHZ 45W 266MHZ BARTON CPU OEM
    May have to replace my cpu with the mobile version (still 45W!). And that probably won't work in the m/b I have. Maybe I will be going the VIA route after all.

    Apparently the high end Intel CPU's hit 236W under load nowadays with the AMD 64 90nm being about 130 (if I remember the article correctly).

  10. #50
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    This one here is only a 35 W barton 2200. This one is a slot A, which up until now was relatively hard to find. I was origionally going to go this route with a micro board . They do not make the specs on these mobile processors readily available unless you sign an NDA. I am going through that process now but I have estimated 3.6A (estimated from the specs available on the non mobile models), which might fit your needs. You are going down the EXACT same path as me as far as choosing a mobo, psu and processor. Soon you will start calculating if the 500 bucks it will cost you would be offset by the opus 150, that barton, and your mobo. Hehe your probably doing that right now.

    With that processor and opus you will be ok (or even the 200W clip in if you can figure out a way to regulate it). I am going the via route because of space (not a lot of room in a G35 trunk). But if I had a truck or something with a decent trunk I would get that processor with the opus.

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