Battery powering fans

Discussion in 'General Hardware' started by GreatestOne, Oct 30, 2015.

  1. GreatestOne

    GreatestOne Limp Gawd

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    Hey guys... ok not sure if this belongs here but kind of an odd question.

    I would like to use some of my case fans that have the standard connectors (to the MB) for another purpose and would love to have them run off batteries, any batteries for now but might need a 9V to really spin them at max speed... not really an electric experts so I need some suggestions on how to run a case fan via batteries and get the most RPM's out of it, since it should be easy to downgrade from there.

    Thanks!
     
  2. michalrz

    michalrz 2[H]4U

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    PC fans mostly require 12 Volts of DC voltage. You can go down to around 7V and most will still work fine. Lower than that usually causes them to fail to spin up.
    RPM can be controlled either by manipulating the Voltage or by rapidly turning it on and off.

    The only battery that could pull this off is a UPS rechargable lead acid one. They normally put out 12 volts and have about 7 ampere-hours. Look at the sticker on the fan - it probably says something like 12V, 0.2A. That's a fifth of an ampere. So 7 AH would give you around 35 hours of spinning (7 / 0.2).

    But batteries can be dangerous inside a metal PC pase or otherwise, because their short-circuit current is huge. If a wire were to accidentally fall on the battery and short its + and - terminals then it would almost vaporize in an instant. So, it's a fire risk.

    You always have the option to power your fans by using the yellow wire from a molex plug as the positive (it carries 12V) and the adjacent black wire as the negative.

    Or, Use the yellow one as positive and the red one as negative. The red one carries 5V, so between 12V and 5V there's 7V to be had which is enough to power most fans and slow them down considerably.
     
  3. GreatestOne

    GreatestOne Limp Gawd

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    Hey man, thanks for the awesome info... problem is I think I dont "understand" half if it LO< sorry.... I'm much more of an ME and an EE.

    Ok lets start with what I know... one fan I have is 12V and 0.13A... the other one is a 12V w/operational voltage 10.8-13.3V.

    Bottom line, for my little project, I NEED a fan to operate fully with a standard 9V or D cell battery. So then I am assuming the fans I have here are useless for this purpose?

    Then I guess I should ask, in case you know, is there a fan I can get that can be compatible with the batteries I need or do I just need to get one of those handheld personal cooling fans and take it apart?

    Thanks again.
     
  4. GreatestOne

    GreatestOne Limp Gawd

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    Hmmm interesting, nice options to have... but I assume none of these come in rechargeable format? These are kinda expensive to keep replacing... would you have any idea how many life hours one of my fans mentioned above would have on the cheapest 1300mAh battery? Would it simply be 10hrs for the 0.13A fan?
     
  5. michalrz

    michalrz 2[H]4U

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    12 volts, one ampere-hour (12V, 1AH) is saying 'capable of putting out 12 Volts at one ampere of current (1A, or 1000 mA) for one hour'.

    1300 mAH is 1.3 AH.

    So if a fan draws 0.13 of an ampere, and there's 1.3 of amperes available for one hour, it will take it indeed 10 hours to deplete it (in theory).

    The problem with putting a battery inside a PC is that there's a lot of metal there and if some of it were to directly connect the battery's terminals, it will short circuit - the only resistance in the short circuit is the piece of metal and the battery itself. Both might fry :D
     
  6. Nenu

    Nenu [H]ardened

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    Many people run 12V fans at 7V and even 5V for some.
    I have a few 12V fans running at 7V.

    Why dont you try.
     
  7. michalrz

    michalrz 2[H]4U

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    Iif the fans are supposed to spin when the PC is on, I'd advise using the molex plug of your PSU as the power supply (the one with four thick prongs, used to power pre-sata HDDs). Yellow is +12V and Black is 0V (ground, or 'negative').

    If you want them spinning when the PC is off, you might have to find a fan that runs off 5 Volts (there are some out there) and perhaps use the charging USB port of your motherboard. USB provides 5 Volts even when the PC is off.
     
  8. Zepher

    Zepher [H]ipster Replacement

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    those are rechargeable batteries.
    I used to have a bunch of batteries and chargers when I was doing the RC car thing. I got rid of all of my stuff last year since I wasn't using them anymore.
    [​IMG]
     
  9. Zepher

    Zepher [H]ipster Replacement

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    He doesn't say these are going into a PC, he said he wants to use the PC fans in an alternate fashion.

    A LiFe battery is a safer option as the LiPo batteries I posted above have a voltage range the batteries need to stay in otherwise they get damaged. A LiPo cell's range is 3v - 4.2v and 3v is the absolute lowest you would drain the battery to. My RC cars electronic speed controllers have
    settings to cut the power when the voltage gets down to a set level, I had mine set to 3.6v/cell (10.8v for a 3S pack, 3.6x3=10.8, the S denotes the number of cells in the pack)
    http://www.amazon.com/HobbyKing-150...id=1446255388&sr=8-1&keywords=3s+life+battery
     
    Last edited: Oct 30, 2015
  10. GreatestOne

    GreatestOne Limp Gawd

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    Yes this is for an independent project, sorry if that weren't clear... everything will probably be going in an isolated plastic case, no fire hazard or anything like that would be relevant.

    So this one u posted most recently, I can get that and plug my fan directly into it? I assume I will have to get a switch if needed separately and a charger? I am unfamiliar with these power setups (never got into RC's even tho I always wanted to), can you suggest to me each component to get this working?

    Also, will this run the fan at pretty much max speed, or how do I do that or know the limits? I don't care of I blow the fan, I got a few here, but I do need to maximize the RPM.

    Also, I may need to blow the air through a filter, a little thicker than the ones in a standard PC, so just in theory, would putting 2-3 of these fans back to back increase the CFM of air blown through such filters?
     
  11. Zepher

    Zepher [H]ipster Replacement

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    here is a multipurpose charger for $20,
    http://www.amazon.com/Battery-Balan...8&qid=1446256804&sr=8-2&keywords=life+charger

    you would want to wire up a switch and make a harness so you can unplug the battery for charging.
    here is a simple rocker switch, http://www.amazon.com/SPST-Black-Sn...qid=1446256900&sr=8-15&keywords=rocker+switch

    You can always make a pack with these, http://www.batteryjunction.com/tene...JuRTGdtsPYCIOAlc_aGnu0ry6dQyL2jS44aApZV8P8HAQ
    Pack will be 12.6 volts when fully charged.
    you will need to wire in a protection circuit as well,
    http://www.batteryjunction.com/tenergy-pcb-32005.html
     
    Last edited: Oct 30, 2015
  12. Red Squirrel

    Red Squirrel [H]ardForum Junkie

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    Is there a reason you can't use a small 12v lead acid battery? It will have much more energy density than a 9 volt battery and you can have it hooked up to a 13.5 volt source in parallel to keep it charged. 13.5v is the typical float voltage for a lead acid battery, that means that the battery will naturally keep itself charged without overcharging. It's also referred to as trickle charging.

    As mentioned just be careful not to short it out, I would make sure there is adequate protection to stop the terminals from touching anything metal. Idealy they should be taped up or the battery stored in a separate plastic container.
     
  13. GreatestOne

    GreatestOne Limp Gawd

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    So these solutions seems great for a one time experiment, but for the long term, I would really prefer to use a standard 9V or similar battery that anyone can buy at a store for pretty cheap. But it seems that will seem a bit unruly for these types of fans...

    Cost effectiveness is a big part of this project and now with all this info, I just don't think there is a cost effective way to activate a case/system fan with cheap batteries easily... does this seem correct?

    If that is, I will have to really give up on using these surplus fans I have and suck it up and just buy some battery operated fan like this
    http://www.amazon.com/Travelon-3-Speed-Folding-White-Size/dp/B003DGPWLK/ref=sr_1_7?s=home-garden&ie=UTF8&qid=1446258337&sr=1-7&keywords=portable+fans+battery+operated&refinements=p_72%3A2661618011
    and use it instead? It seems kinda weak but cant be that much weaker than the system fan I would say, even with AA batteries.

    Thanks for working with me guys, this is really helpful.
     
  14. Nenu

    Nenu [H]ardened

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    You are confused.
    I stated the voltages fans can operate at.
    Only you mentioned PC.
     
  15. Zepher

    Zepher [H]ipster Replacement

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    I am not always confused, but when I am, I click the wrong quote button.
     
  16. Mr Evil

    Mr Evil n00b

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    A DC-DC converter will get you 12V from a 9V battery. You can find these very cheap on eBay*. Note that 9V batteries don't have much capacity; if we assume someone buys the cheapest possible battery which will be about 300mAh, that the battery averages about 7V while it's discharging, and that the fan draws 120mA, then you will get about an hour and a half of run time.

    *Quality of Chinese electronics on eBay is quite variable. I'm not endorsing that particular one, it was just the cheapest I found.
     
  17. GreatestOne

    GreatestOne Limp Gawd

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    Ya with all this it seems using my system fans is just not realistic for the long run in my little tunnel fan... I guess I'll just get something like this
    http://www.amazon.com/dp/B003DGPWLK/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=2X2YDD7TL960N&coliid=I1B7RA5XXOGPMP&psc=1
    and just make do from there... always trying to figure out new uses for these surplus system fans I have but seems like a pain and costly to even try to use them, ugh.

    For you other who have this type of situation, LMK what creative or real world ways you are using your system fans that are not being used in a computer.

    Thanks for all the input, really helpful!
     
  18. CaptNumbNutz

    CaptNumbNutz Bulls[H]it Master

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    Assuming your standard Alkaline batteries (energizers, duracells, etc.):
    9V batteries provide 9 volts and around 500-1000 mAh (milliamps per hour). In other words, you won't be running a fan for very long with one (few hours at most if its a small fan). A .13amp (.13 Amp hour = 1300mAh) fan will run a 9v down in less than an hour.
    You will need one of these if you go this route.

    One D cell battery supplies 1.5 volts and 12,000+ mAh. You will need 8 D cells to run your average PC fan (8x1.5=12), but it will run for half a day.
    You will need one of these if you plan to go this route.

    Please be aware I am only estimating those run times using those battery types. Using alkalines is the simplest option, but you can definitely power this by other means like rechargeable batteries. If you are considering 8 D cells, keep in mind just how big those batteries are and how much space 8 of them will take up. At that point you might as well consider some cheap 12v rechargeable gel cell battery they put in UPS power supplies.
     
    Last edited: Oct 31, 2015
  19. GreatestOne

    GreatestOne Limp Gawd

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    Thanks, ya I was considering all that and I severely underestimate the power needed to run a system fan LMAO, totally disrespected it. I will have to save all of these for a rainy day and just buy some lower powered fans... even if I got it working with all your suggestions, it really wouldn't be practical in the long run unless I can somehow find a way to invent an auto-off/on feature for my contraption. Its possible, but I first need to test if the concept works and then worry about the other stuff.

    I may have asked this before but anyone know if stacking 2-3 fans together will produce more "pulling/blowing power" through a filter than just 1? I understand they cant possibly increase CFM or air speed, but wouldn't it power air through a thicker filter much better? Its been a while since MechE but intuitively I feel like it should work LOL.
     
  20. Zepher

    Zepher [H]ipster Replacement

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    you don't need to invent an auto-on/off feature, depending on what you need you can use a thermal switch, clock timer, photo sensor, relay, or remote control.
    what is your contraption actually going to be doing.
     
  21. Ocellaris

    Ocellaris Ginger @le, an alcoholic's best friend.

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    I am glad someone finally asked this. Whatever the OP is trying to do, better advice can be given if people know the actual goal here.

    I once kept a reef tank going through a long power failure by using a rack mount UPS and light timers. It wasn't very efficient however it worked fine.
     
    Last edited: Oct 31, 2015
  22. GreatestOne

    GreatestOne Limp Gawd

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    Ya I know, but I been holding that back for a reason... its for an invention and I cant disclose the details for obvious reasons while I work on the prototype. But I will promise as soon as I get a patent approved I will upload photos and videos and description here to show you the function!
     
  23. GreatestOne

    GreatestOne Limp Gawd

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    Wow those minis, holy cow, so cute. However I think with their CFM I might as well blow with my mouth LOL... great site!

    I found this
    http://www.digikey.com/product-detail/en/E1225M05B-FSR/1570-1046-ND/5209743

    So this fan is rated at 5V, 67 CFM, 600mA.

    If I get one of those 4x"D" battery holders for 6V supply (is that bad, i.e., does it have to be exactly 5V?), then my fan should last about 4.5 hrs of continuous use, which I think is in the ballpark of my accepted specs.
     
  24. Skillz

    Skillz [H]ard DCOTY 2017

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    1V wont hurt it. However you can easily build a regulator that will take 6V down to 5V. I'll see if I can find something for ya.

    edit
    here ya go
    http://www.instructables.com/id/5v-Regulator/

    This will easily convert 6v input to 5v output.
     
  25. GreatestOne

    GreatestOne Limp Gawd

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    Thanks a ton for this info, I feel like I am back in college working on a circuit board, if u can even call it that with this.

    I dont understand tho, why make a DC fan at 5V and not 6V? What do they expect u to do with a 5V... is that a much more common voltage for like RC's or some other hobby I dont know about that uses such proprietary batteries?

    If I dont use the regulator, will there be a chance of burn or massive overheating/danger?

    I'm almost thinking of trying the 8xD cell config and just getting a 12V fan instead, might actually be LESS work, although thats a lot of batteries and rather just use 3 or 4.

    I found this

    http://www.digikey.com/product-detail/en/FAD1-12738CBHW12/FAD1-12738CBHW12-ND/2600667

    at 12V, 650mA at a nice 161 CFM....
    So with 8xD's, about 15 hrs of juice for a lot of air moved.... or C batteries for about 7 hrs, hmmmmm...

    I'm assuming the leads from the fan will just plug/connect to the leads at the bottom of the battery holder? I can solder but rather not while testing etc.... I think I saw a little hole in the metal lead out the battery holder.
     
  26. stormy1

    stormy1 [H]ard|Gawd

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    5v is/was the standard ttl voltage and is still used as a base voltage in many devices.
     
  27. GreatestOne

    GreatestOne Limp Gawd

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    Is ZnMnO2 the next evolution of NiMH rechargeables... Assuming higher capacities and better charge-holding?

    It just seems odd that the 1.5V is the standard for DC energy but a device would use 5V, I dont like that math, just wondering how that came about.
     
  28. Mr Evil

    Mr Evil n00b

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    As that is a linear regulator, it requires an input voltage greater than the output voltage. For the particular one used there, the difference needs to be at least 2V, so it won't step 6V down to 5V. Low dropout regulators need less difference, and could work with a 6V input.

    However, although batteries are nominally 1.5V, they fall below that very quickly (the datasheet provided by stormy1 shows this). The total voltage from 4 x D cells will at some point fall below 5V, so even a LDO regulator won't work.

    It might be ok to just run a 5V fan straight off the batteries. The speed will vary as the batteries go flat, and you'll need to check the datasheet to make sure it can handle the initial 6V, but this is the simplest solution. Otherwise you will need a buck-boost regulator, which is capable of putting out 5V when the input voltage is either above or below 5V.
     
  29. Zepher

    Zepher [H]ipster Replacement

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    What kind of invention requires a fan or fans powered by batteries that blows through a mesh filter?
    Are the fans going to be cooling something else that is also battery powered?
     
  30. Nenu

    Nenu [H]ardened

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    It doesnt need to be in operation for long and will be too big for a handbag so wont be a personal everyday item.
    It probably wont be underwater as its air source is not renewed, it is unclean air.

    Something that needs cooling with clean air and cannot/wont have a heatsink attached, but has a large enough surface area for air cooling to be effective.

    Or something that has to operate in a dirty environment.
    Perhaps a mini monitoring station in an industrial application.
     
  31. GreatestOne

    GreatestOne Limp Gawd

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    Thanks for your input.... but when u say "check the datasheet" I dont understand because in all these specs I only see a voltage parameter and nothing else about what initial voltage it can handle up to etc....

    Its more like a odor filter, so the filter itself will be kinda thick, not like a computer dust filter... u know, like the filters used in those air purifier things. Thats why I wanted to make sure if putting say, two 5V fans back to back would actually be more efficient than putting one big 12V... obviously I can manually test with a garbage bag or something and test CFM for each but asking here just in case someone has at least a theoretical knowledge of air flow and resistance. I feel like I can come up with some equation for this but I am kinda stuck as to how to handle back to back fan advantage.
     
  32. Nenu

    Nenu [H]ardened

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    Think of a single high rpm fan like engine horsepower and lower speed dual inline fans as engine torque.
    When pushing through a restrictive medium, dual inline fans will work better.
     
  33. GreatestOne

    GreatestOne Limp Gawd

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    I can visualize that, but would love to know a equivalency formula where something I can calculate that

    2x 5V 70 CFM fans
    =
    1x 12V 150 CFM fan

    Know what I mean?

    And I guess with the 2 fans in series, that means the system is still at 5V but the amp draw is more = batteries will work but last half as long?

    Gezuz, flashes of high school LMAO
     
  34. Zepher

    Zepher [H]ipster Replacement

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    technically, 2 fans in series (wired in series) would be the same amp draw but will spin at half speed.
    2 fans inline wired in parallel would be same voltage and double the amp draw.
     
  35. Mr Evil

    Mr Evil n00b

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    There are links to datasheets on Digikey's site on each fan's page. The better manufacturers specify both a minimum and maximum voltage. The lazy ones give only a single nominal figure.
     
  36. stormy1

    stormy1 [H]ard|Gawd

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    static pressure is going to be a large problem and a bigger issue than open air cfm.
     
  37. stormy1

    stormy1 [H]ard|Gawd

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