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Thread: you dont necessarily need a voltage regulated PSU

  1. #1
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    Exclamation you dont necessarily need a voltage regulated PSU

    the tittle may or may not seem a little controversial but ive found it to be true. i dont need an expensive PSU, even if i could get hold of one, or to gracefully handle my PC startup/shutdown. I went for the ultra small, cool running 200W snap-on PSU, great form factor.

    I dont worry about all those little problems concerned with comming out of hibernation, could care less if my USB devices remain powered or not and can use my carPC for hours on end with or without my engine running and startup times are measured in just a few seconds. Ive found another way to power my carPC and screen, totally separate from my car battery, theres plenty of it about and its totally free.

    a slight proviso up front though, this technique may not be for everyone but it works just fine for me and the problems just melt away.

    ive never been a fan of powering anything from a cranking battery, they're designed to give a big kick when you turn the key and thats it. trying to get 240V to my tent one summer led me to deep-cycle batteries. a different animal, designed specifically for steady power drain all the way to empty with no real adverse effects. i use the factory fitted charging electrics in my car - im pretty sure all cars have them - to charge it up using a $15 split charge relay. the charging electrics go all the way from the alternator to the back of the car and would normally connect up to a tow bar if one was fitted, their role is to charge a caravan battery while you're towing it.

    i always shudder at the thought of putting a lead-acid battery anywhere near the inside of my car, deep-cycle or otherwise, and would never do it on a permanent basis, but gel batteries are different again. you can put them in upside down if you want and are much more resilient to long periods of discharge.

    gels are normally three times the cost but this is where the free bit comes in. gels are used in wheelchairs so i rang up a wheelchair repair place. it turns out that wheelchair owners are particularly paranoid about running out of juice so they regularly replace their batteries leaving this bloke with rack fulls of nearly new batteries he cant get rid of. he gave me a 110 amp hour battery for nothing, not as big as you'd think but anyway ive got a big SUV so boot space isnt an issue. theres a whole range of sizes though, right down to 25 amp hour one which is not much bigger than an ATX PSU.

    the next bit is why you dont need a power regulator. the normal procedure is for the charging electrics to only get power once the car battery is fully charged, it gets priority, it means these electrics are fully isolated and switched off during and for a short time after cranking, so, no voltage spike. meanwhile, and even during cranking your carPC has all the power it needs from being connected to your second battery, all it sees is a smooth constant 12V, probably going up a few tenths of a volt more when the charge power eventually comes in.

    the upshot of all this is my carPC can be used just as i use my computer at home, just push it to S1 standby when i dont need it or just leave it on, my PSU runs cold so theres no heat build up. ive got a 100 amp alternator that very quickly re-charges any depletion in the gel once i get driving again.

    worse case scenario is i dont start my car for three days and forget to power down the PC, the gel does flat, so what, the split charger isolates my car battery so the car starts as normal, it then gets to work charging the gel.

    i went back to the wheelchair bloke and took over 1500 amp hours worth of batteries, im going to create one hell of a UPS for my home network, didnt cost me a bean.

  2. #2
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    That's really cool. Thanks for that info. I'll have to check my local powered wheel chair reseller. Great newB post!

    ...but, about the not needing a regulated power output...
    Do you use a power inverter into a ATX power supply? If so doesn't the PSU regulate the power? Your title makes it sound as if you just plugged the the output from the gel battery directy to your PC components.

  3. #3
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    Yea! great post! I was jus about to post something like this. I had been talking to my grandfather and he said that he had a RV (the tow kind) and he ran all of the 12V electrics off of another battery that he wired to the cranking battery with a diode on the the other side of the alternator. That way you get all of the benefits of the alternator to charge and you don't have to worry about your cranking battery ever draining. Then, you can just run a 3 prong molex into the car and put a surge protector on it and have lots of things running on the inside if you like. I think it's a much better and much cheaper solution. Great post.

    and yes, i think that he can just plug straight up from the output to the pc components, espcially if you run the plug into the car.

  4. #4
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    Quote Originally Posted by ppgt94
    That's really cool. Thanks for that info. I'll have to check my local powered wheel chair reseller. Great newB post!

    ...but, about the not needing a regulated power output...
    Do you use a power inverter into a ATX power supply? If so doesn't the PSU regulate the power? Your title makes it sound as if you just plugged the the output from the gel battery directy to your PC components.
    yeah, thats just what i did, works fine, no problems. im also using a 3.5" hard disk which im told is a definite "no no" with unregulated supply since they use the 12V output to regulate their speed, again, no problem, the output voltage stays keen and steady. Im also not getting any alternator noise at all, dont even need a ground cus im connecting directly to the negative terminal of the gel.

  5. #5
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    Quote Originally Posted by ppgt94
    That's really cool. Thanks for that info. I'll have to check my local powered wheel chair reseller. Great newB post!

    ...but, about the not needing a regulated power output...
    Do you use a power inverter into a ATX power supply? If so doesn't the PSU regulate the power? Your title makes it sound as if you just plugged the the output from the gel battery directy to your PC components.
    ive got sooooo much out of this forum, im glad ive managed to give something back

  6. #6
    FLAC ppgt94's Avatar
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    Quote Originally Posted by bigbertha
    yeah, thats just what i did, works fine, no problems. im also using a 3.5" hard disk which im told is a definite "no no" with unregulated supply since they use the 12V output to regulate their speed, again, no problem, the output voltage stays keen and steady. Im also not getting any alternator noise at all, dont even need a ground cus im connecting directly to the negative terminal of the gel.
    So if you're using a PC power supply that regulates the power. So it's like this --

    Battery -> Inverter -> AC Power Supply?

    If so this is nothing new.

  7. #7
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    Quote Originally Posted by ppgt94
    So if you're using a PC power supply that regulates the power. So it's like this --

    Battery -> Inverter -> AC Power Supply?

    If so this is nothing new.

    i believe it is in the fact that everyone else is talking about very expensive OPUS power supplies and the like. In this case, you just go buy (or get one from the wheelchair guy) a battery, hook it up with a diode on the other side of the alternator and you have what amounts to a very reliable and chargeable power supply. This offers, imho, a cheaper and better solution, especially if you are using a laptop.

  8. #8
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    You still need to buy an inverter. This is what most of us were doing before the Opus if we didn't build our own DC-DC power supply.

    I like the tip on where to find a cheap (or free) battery though!

  9. #9
    ptk
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    Quote Originally Posted by ppgt94
    You still need to buy an inverter. This is what most of us were doing before the Opus if we didn't build our own DC-DC power supply.

    I like the tip on where to find a cheap (or free) battery though!
    think he is not
    he is using 200w snap on ones.

    kao
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    CarPC Ver 4 completed. Aopen i45GMT-HD, C2D mobile 2GHz. Photofast 64GB SSD. Novatel EU-850D

  10. #10
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    Gel cells are great batteries. My Dad used to use them for EVERYTHING. Anything that took batteries would get a connector put on the back and would be powered with them instead of regular batteries.

    He also used to make flashlights with them. Best one was with some 3" PVC and a motorcycle headlight bulb. That was the brightest rechargable flashlight...
    89 Mustang (Autox, road race, and cruiser)
    93 Escort (Daily Driver)
    84 Dolphin RV (Soon to be Carputer Heaven)

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