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Thread: Battery power

  1. #1
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    Question Battery power

    I just started looking into the idea of putting my old pentium 133 mhz computer with an sb16 into my car to play mp3's and I am pretty new to the idea of doing this. I would like to put the system in the car as is and I was wondering how much of a drain this is on the car battery. After reading around it seems that I would use a 140w or 300w inverter but i am worried about having to replace my battery often. I know someone that has a very small computer connected to their car and they had to replace their battery every year so it would seem to me a desktop would drain the battery even more. Does anyone have any info on this?

  2. #2
    Retired Admin Aaron Cake's Avatar
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    Cool

    If you use the computer with the car running, it will not drain the battery at all. Instead, it will be powered by the alternator. If you run the computer with the car off, however, it will drain the battery in a day or so. How long it takes depends on the size of your battery.

    Oh, and inverters suck. Use a DC-DC converter.

    And it sounds like your friend had something else wrong with his car (faulty alternator/voltage regulator, current leak, etc....).


    ------------------
    Aaron Cake
    London, Ontario, Canada

    Player: Cyrix 200, 32MB RAM, 10.2Gig Quantum HD, Onboard EtherNet/Sound/Video, Custom Lexan Case, Win95 Kernal w/Custom Player
    Car: '86 Mazda RX-7 w/Basic Performance Upgrades
    Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
    Car: 1986 Mazda RX-7 Turbo (highly modded), 1978 RX-7 Beater (Dead, parting out), 2001 Honda Insight
    "If one more body-kitted, cut-spring-lowered, farty-exhausted Civic revs on me at an intersection, I swear I'm going to get out of my car and cram their ridiculous double-decker aluminium wing firmly up their rump."

  3. #3
    DJ
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    hehehe Aaron

    about inverters sucking...

    i am pretty confident that DC-DC's are better, but i have a 160W inverter and it works great!!


    .peace.

    dj

  4. #4
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    z3r0 good DC converters will take around 3-3.5 amps of current when starting up and around 2-3amps when running... so i guess in some way in-car mp3 players take less amps then normal car decks

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    Fosgate
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  5. #5
    Raw Wave wizardPC's Avatar
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    this is how i look at it:
    inverters are about $60 (here, anyway)
    normal PSU's range from $5 to $50

    the dc-dc power supply from arise is $79

    its easier and (sometimes) cheaper to go ahead and get the dc-dc power supply

    as far as battery drain--Aaron, i have been a big fan of your web site for a year or so, so i trust what you say. i have to ask this though: if the computer goes on suspend, will it drain all that much?
    can someone write a program using the parallel port's inputs to have the computer go to suspend when the car turns off?
    the battery in my truck is i think an 800 amp battery, and i think i need 400 to get my starter to work. i am aware of the concept of amp hours, and i was thinking that if in sleep mode the computer uses 1 amp, then i can go for up to 16 days without starting my vehicle and it will still start. How far off am i?
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  6. #6
    Retired Admin Aaron Cake's Avatar
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    Originally posted by wizardPC:

    as far as battery drain--Aaron, i have been a big fan of your web site for a year or so, so i trust what you say.
    Thanks! That's nice to hear!

    i have to ask this though: if the computer goes on suspend, will it drain all that much?
    It shouldn't draw more than about 20W. This will vary depending if you have a DC-DC or inverter. Assuming the whole machine goes to sleep (all fans off, HD off, etc.) then current will be very low. ATX machines are much better at suspend than AT machines.

    can someone write a program using the parallel port's inputs to have the computer go to suspend when the car turns off?
    I thought of this when I was making my player, but didn't do anything about because I didn't have the time. It should be rather easy though. All the information is on my site :-). If you need help, just post and I will try. I have all the info on the needed API calls.

    that if in sleep mode the computer uses 1 amp, then i can go for up to 16 days without starting my vehicle and it will still start. How far off am i?
    Roughly, that's how it will work. However, we need to move out of the theoritical into the real world battery. Let's just assume that your battery will power your player for three days straight. The reasons are complicated, and I do not have time to type them (same reason my page hasn't been updated in over a year....)...


    ------------------
    Aaron Cake
    London, Ontario, Canada

    Player: Cyrix 200, 32MB RAM, 10.2Gig Quantum HD, Onboard EtherNet/Sound/Video, Custom Lexan Case, Arise DC-DC, Win95 Kernal w/Custom Player
    Car: '86 Mazda RX-7 w/Basic Performance Upgrades
    Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
    Car: 1986 Mazda RX-7 Turbo (highly modded), 1978 RX-7 Beater (Dead, parting out), 2001 Honda Insight
    "If one more body-kitted, cut-spring-lowered, farty-exhausted Civic revs on me at an intersection, I swear I'm going to get out of my car and cram their ridiculous double-decker aluminium wing firmly up their rump."

  7. #7
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    I'm using a 300w inverter and my computer can go about 8 hours without the car running before draining the battery to a point where the car won't start (yes, it has happened). I have my inverter wired directly to the battery and a switch in the dash to turn off the inverter, which is in my trunk. If I'm stopping for gas or at 7-11 to get a coke I leave the thing running so I don't have to reboot. If I'm stopping for more than about an hour, I'll turn it off. Sometimes I forget to turn it off, though, so I got a Priority Start battery protection system ($59US)which shuts down the car's electrical system if the battery voltage gets so low that it might not have enough to start the car. That way the battery is protected from full drain and the car always starts. It has saved me a couple of times. If anyone's interested the link to the cheapest place to get the PriorityStart is http://www.4unique.com/battery/prior...rity_start.htm

    By the way, I love the inverter. It's in my trunk, so noise is not a problem. Plus, when I need to work on my car player, I simply take out the player and plug it in at home and off I go. I got a 300W Tripp-Lite for $49. Works great.

    [This message has been edited by Kevin (edited 08-23-2000).]

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