Computer/axial Fans & Laptop Power Supply

Forgive me for spamming; this is a repeat of a question that I thought might get a quicker answer if it had its own thread. (I think) I'm all ready to go except for this issue and, since I'm out of meds, I'm kinda chomping at the bit to get my medicine cabinet going. OK, so ...

I have a 25v laptop power supply hooked up to 3 12v axial fans to cool my 150w HPS in a DIY cooltube.

I strung the 3 fans together before splicing them to the adapter but, only the one closest to the power supply is spinning. There was barely, barely enough wire to hook them together so I cannibalized wire from another 12v fan to make them reach the power supply. This happens to be the link to the 2 non-operational fans. Coincidence? Or, not heavy enough wire? It's awfully skinny.

I also have a 4th fan I want to mount for circulation. Is 25v supply adequate for the 4 fans? Overkill?

How can I get all 4 fans to go? I have an old car/air pump that we used to use for the air mattresses when camping. Can I use the wire from that to hook the fans together and then to the power supply? If not, I'll have to swing by "the Shack" for the correct wire, whatever it is. Too bad I can't just go ask them, isn't it?
Thanks in advance ...

Rambunctious said:

Forgive me for spamming; this is a repeat of a question that I thought might get a quicker answer if it had its own thread. (I think) I'm all ready to go except for this issue and, since I'm out of meds, I'm kinda chomping at the bit to get my medicine cabinet going. OK, so ...

I have a 25v laptop power supply hooked up to 3 12v axial fans to cool my 150w HPS in a DIY cooltube.

I strung the 3 fans together before splicing them to the adapter but, only the one closest to the power supply is spinning. There was barely, barely enough wire to hook them together so I cannibalized wire from another 12v fan to make them reach the power supply. This happens to be the link to the 2 non-operational fans. Coincidence? Or, not heavy enough wire? It's awfully skinny.

I also have a 4th fan I want to mount for circulation. Is 25v supply adequate for the 4 fans? Overkill?

How can I get all 4 fans to go? I have an old car/air pump that we used to use for the air mattresses when camping. Can I use the wire from that to hook the fans together and then to the power supply? If not, I'll have to swing by "the Shack" for the correct wire, whatever it is. Too bad I can't just go ask them, isn't it?
Thanks in advance ...

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well i think 25v is a lil to much for a 12v fan.. its 12v for a reason if u use much more on it u will burn it out... u can wire them up right so that they arnt using the full 25v... if u plug red fan wire to positive on laptop charger and the black on the next fans red wire then the black wire of that one to the red of the next and then the black to the black on the laptop charger.. i know when that is done they split the 25v..... otherwise yeah a fin might work for now but its ganna try to run harder then it needs too and burn out way to fast

i have been thinking about using comp fans in my storage chest which i plan to use for veg plants. can anyone explain how this is done? so just from reading this thread i find that i'd have to splice the fan wires but whats this adapter you talk of?

drunkenmonk, I got the idea to use a laptop AC adapter to power SEVERAL fans from cyphercrash's thread .

crazy7605150 said:

if u plug red fan wire to positive on laptop charger and the black on the next fans red wire then the black wire of that one to the red of the next and then the black to the black on the laptop charger.. i know when that is done they split the 25v.....

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Sorry for the dummie questions but, this setup is a threat to the charger, or to the fans? Because, noooooooo, not my precious cooltube fans! This is why I haven't turned any of it on for very long.

I just read another 11 pages on using computer fans but, I'm still having the prob with one fan going and the others not going ... I tested them before going to all the trouble to put the cooltube together. I probably just need more wire, but only a foot or two. What to cannibalize this time? How 'bout some garage door opener wire? Too bad I gave away my box of old AC adapters not too long ago. Only had them for about a decade! LOL

So, you're saying to wire the fans like this to spread out the volts? "In tandem," right? Wow. Black to red. Not used to working with DC, obviously ... can barely function with AC where all the colors are supposed to match. I'm a visual learner. Thanks for your patience, crazy.

OK so, I redid the wiring like this:

1. charger to fan, black to black
2. fan to fan, red to black
3. fan to fan, red to black
4. fan to charger, red to red.

Al B.'s illustration is better than mine.
https://www.rollitup.org/do-yourself/4105-computer-fan-wiring-5.html#post119652

Now none of the fans works. The charger sparked a little when I plugged it in. 3 x 12v = 36v. I used my little 5v cell phone charger to test one fan, and thankfully, it still works. Did I fry my 25v charger? Do I now need a 36v charger?

Here are the fans I'm using, if it helps you help me.

Try wiring as per his bottom diagram.. You're only running those fans at like 1/2 power.. Perhaps its just not enough..

born2killspam said:

Try wiring as per his bottom diagram.. You're only running those fans at like 1/2 power.. Perhaps its just not enough..

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Thanks, B2KS. That's how I had 'em hooked up to start with, when one fan was going but the other 2 weren't. By the way, my charger output is 19V, 4.74A and the 4 fans are DC 12V, 0.30A. Bad for the fans?

I didn't want the clutter or the heat in my box but, perhaps that would be the safest and easiest thing to do would be to get a wall wart for each fan?

Otherwise, if I say so myself, my (flowering) cab is coming along nicely. Finally got it lightproofed today. My moms aren't quite ready to have offspring yet anyway so, I've got some time but, I can hardly believe the number of hours I've put into this thing -- no wonder the plugNplay boxes aren't cheap! LOL

OK, here's how I had them wired together in the first place. I had to tie the 2 to the left with another strand to the one on the right and then hook them to the power. The one on the right worked (pushing), the 2 on the left (pulling) did not.

The volts and amps of the power supply and the fans are in the post I made last night. I thought, for sure, someone would be able to help me here?

ok well first off u dont want to put to much power into the fans.... if its more then a 12v charger its not the best.... and it would not equal 36v if linked up in tandem they all split the v... so it would be (your chargers volts) divided by the number of fans= volts they are all reacieving... try to find a 12v at a thrift shop of somthing... ok here is a question... have you tryed your 5v cord on each fan??? do they all work right... i dont think it will do anything diff but wire the fans so there is no extra wires... hook fans to eachother then to charger ... u know what i mean...where u only have 2 spots with wires twisted together one on red and one on black

That should work, check your connections.. Assuming specs work out, you'd be driving the fans at roughly 2.5x rated power, and drawing ~1.5A from the 19V psu, and the whole thing should consume ~30W..
That psu will drive any 12V device at 2.5x power when its hooked up alone or in parallel btw..

BTW 5V won't necessarily get a 12V fan spinning.. It might, and it might kick in with a little push start, but not necessarily.. If they work (which they probably do since most dc fans can typically handle ALOT of voltage abuse) you'd likely be able to detect a tad bit of magnetic force though if you wiggle the blade even if it won't start..
If the extra power is going to be a problem it'd be in noise, and mechanical stress.. Some spin nicely when overpowered, others rattle to death..
You could wire a resistor in series to the parallel configuration to drop the power if its a problem

when wiring DC fans, you need to look at 2 things, voltage & amperage
when wiring fans in parallel(all reds together,all blacks together)the voltage will stay the same to all fans but you need to add up the amperage to get a power supply big enough -if each fan draws 100 milliamps, then 3 fans will draw 300 mills @12vdc
if wired in series, from powersupply to 1 red,that fans black to the next fans red,its black to the next fans red & finally its black to the power supply, the amperage will stay the same but the voltage will be devided by the # of fans so your 25 volt powersupply will give each fan about 8.3 volts.
most DC fans will work over a good range of voltage so a powersupply from 8-16 volts will be OK
the best way is to wire in parallel w/ all the reds going together to the power supply and all blacks going to the other side of the powersupply.
find a power supply that has the voltage you need & double the amperage needed to ensure safty & long life of the supply.I have melted a 500 miliamp transformer by drawing 400 milliamps for a few weeks through it in a hot location.
finding a powersupply should be easy,what house doesn't have a few dozen transformwers laying around from old phones,games,ect. just read the label and make sure the secondary side has DC voltage in the range you need and plenty of amperage. too high of voltage can burn up your fans but the fans will only draw the amperage it needs, a 48 volt dc power supply will cook a single fan but a 12vdc 1000 milliamp powersupply(transformer) will be fine for a fan that requires 12vdc,and 100 milliamps

crazy, I did test one fan with the 5V charger and, thankfully, it worked. I was too pooped and frustrated to test the other 2 last night so I assumed they still worked, too but, I will do that after I meet some other obligations today.

One problem is, the wires coming out of the fans are too short to put the reds to the the reds and the blacks to the blacks and then string them all to the charger. Also, they probably need to be re-stripped, which will make them even shorter.

I've been studying like a fiend but cannot find anything that tells me: can I put 2 reds together, and 2 blacks together, then splice in a longer wire that will reach the other fan and the charger wire? That's what I tried at first, and it seems like it should work but, it didn't (maybe because of the crappy stripping job) and, I don't wanna burn my house down.

If the "extension" idea will work, can I use the wire from my old 12V air pump (plugs into car cig lighter) work for this? Or, I happen to have some extra garage-door-opener wire ... will that work? If not, I'm gonna have to buy some ... DC wire, right? I just need to know what to ask for without tipping off the gossipy small town clerks.

Regarding the charger, I read that amps are what I should've been adding together. So, with 4 x .30A fans, will Adapter 12V 1,5A AC Power Supply DC Adaptor 1500mA New work? If so, I'll put it on my shopping list. Gads, I just gave a whole bucket of these things away a couple of months ago. Dang me!

From what I can find, the laptop charger I was using should have made all the fans go, even if they'd have spun too fast and burned themselves up. My connections were all good, I think, except for the part where I might have messed up stripping those tiny fucking wires. Possible weak link, right? I will try it with a soldering gun this time - after I get a soldering gun.

Thanks again for all your help. By the time I get this done, I should have some clones ready to go and that can't possibly be too soon for me!

Yes you can add extension wires and wire-splitters etc, just make sure your connections are good.. What mrmadcow said is correct, but your psu should handle the current needed to run them all at its voltage.. Main question is how the fans perform at 25V.. And again, you could add decent sized resistors in series to drop some voltage if 25V is too high for the fans..

Rambunctious said:

can I put 2 reds together, and 2 blacks together, then splice in a longer wire that will reach the other fan and the charger wire? ....can I use the wire from my old 12V air pump (plugs into car cig lighter) work for this? Or, I happen to have some extra garage-door-opener wire ... will that work?

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yes. the above will work. wire size is important. to give you a reference,telephone wire is 22 gauge,a cord on a lamp is normally 18 gauge. for a short distance(under 10 feet)22 gauge may be enough to power a fan (12vdc@ .30 amps) but going larger is safer/better. the airpump would be a better choice because it will be heavier wire.

Rambunctious said:

Regarding the charger, I read that amps are what I should've been adding together. So, with 4 x .30A fans, will Adapter 12V 1,5A AC Power Supply DC Adaptor 1500mA New work? If so, I'll put it on my shopping list.

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it will work but I would consider either going to a 2 amp or 2 1 amp powersupplies. I try to use a power supply rated for close to double my draw.in your case I would go for 2 supplies so if 1 quits, your room wont overheat as quickly- BTW 1000 milliamps = 1 amp

Rambunctious said:

From what I can find, the laptop charger I was using should have made all the fans go, even if they'd have spun too fast and burned themselves up. My connections were all good, I think, except for the part where I might have messed up stripping those tiny fucking wires. Possible weak link, right? I will try it with a soldering gun this time - after I get a soldering gun.

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could have burned up the fans or be a bad splice.instead of soldering the connections,you could use electrical wire nuts, its much easier.- they come colorcoded for the size of wire you are working with.blue or orange should be fine

I didn't see the posts by mrmadcow and B2KS before my response to crazy so, thanks to all for the help!

Too many volts = bad.
Too many amps = not bad?

I put 3 fans in the cool tube for the sake of being redundant so, it makes sense to be redundant with the power supplies, too. Hells yeah! Why didn't I think of it?? LOL

So, I'm after 3 adapters, right?
> 1x 12V/2A+ for the two (.30A) fans pulling from one end of the cool tube
> 1x 12V/1A+ for the other (.30A) fan pushing from the other end of the cool tube and
> 1x 12V/1A+ for the (.30A) circulation fan (so it can run 24/7).

I never did plan on soldering the wires together but instead, I read last night on another forum about how one could use a soldering iron to melt/strip the insulation from those tiny little fan wires. Makes sense, right? I was tempted to use my toaster so it's probably a good thing they're already mounted in the cab. LOL

Regarding wire nuts, check! Much easier and cleaner than taping, especially inside this little cabinet, up behind the cool tube where I already feel like a contortionist trying to get in there.

Shopping list for tomorrow:
1 x 12V 2A+ adapter
2 x 12V 1A+ adapters
Blue and/or orange wire nuts
Soldering iron (to strip wires)

Am I missing anything? Electricity is obviously not my forte. Thanks again for all the help!

it would be good to pick up a little wire... go to hardware store and pick up a roll of it... u can find them pretty easy 18 gauge is good or 16.. its fairly cheap to get... if they ask u, which they wont, tell them u have to fix a charger or something.. oh and a power supply u usually can find a few at thrift shops like salvation army or like places... maybe for like $3-$6

crazy7605150 said:

it would be good to pick up a little wire... go to hardware store and pick up a roll of it... u can find them pretty easy 18 gauge is good or 16.. its fairly cheap to get... if they ask u, which they wont, tell them u have to fix a charger or something.. oh and a power supply u usually can find a few at thrift shops like salvation army or like places... maybe for like $3-$6

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Thanks, crazy. I'll put it on my list. Is it called DC wire?

BTW, do you guys use Freecycle? I was just offered some free chargers. I haven't picked them up yet so I don't know the specs yet, or how many there are but, the price was right! Most areas have a local group whose purpose is to give/request free stuff just to keep it out of the landfill. Google and join, it's cool. Come to think of it, that's where my other box of adapters went. What goes around literally comes around!

You could use phone cord or anything for a dc fan..

wire is wire.... i mean u really prop could use a cable cord like for you tv and it would work... a wire is just metal that links one thing to another ... there is no such thing as dc wire... its just wire... if you cant find it just ask for 16 or 18 gauge wire...

and no prob about the help... what goes around comes around right.... u said it yourself...