I’m a complete noob. I want to connect 6 x 12v, 120mm pc fans together.
Or are pc fans 5v?
I want to charge these with a rechargeable battery… what kind, size do I need?
Thanks
Welcome.
Need to know the specs on the fans, provide link pls.
Also need to know:
- How long do you need to run on a battery without charging?
- Are you stuck on using 12V fans, 5VDC would be easier to design for.
- How much airflow do you need?
- Where/how will the fans be used?
- How are you going to charge the batteries?
- AC power
- DC power
Thanks for the speedy reply. I honestly don’t know much about it. I want, 6 x 120mm fans, and what ever the best volt is… so 5?
It’s a hobby project, similar to a large laptop cooling pad.
I’d like to get a few hours out of the battery before charging, up to 8 or more.
Airflow… I don’t even know how to answer this 
How are you going to charge the batteries? Same as you’d charge your laptop or any other device, plug it into the wall. Would one rechargable battery be best or multiple batteries?
PC fans are typically 12 V, but you can also get these 120 mm fans in 5 V or 24 V versions.
5 V is probably the most convenient option since you can power these directly from a USB power bank.
The label on the fans tells you the voltage and the peak current. That peak value is usually quite a bit higher than the typical consumption. E.g. the label of my solder fume extractor fan says 0.33 A, but it only draws that much if I slow it to a crawl with my finger. Under normal conditions, it only draws 0.2 A.
Anyhow, you have to size everything (boost converters, the power bank, etc) based on these peak values.
For calculating how long the battery will last, you can just use the typical power consumption.
E.g. for six of those fans, I’d need a 2+ A 12 V power source, but it would only draw 1.2 A when it’s running.
2 Likes
Are you prepared to build this thing 
You will need electronics tools; DVM, soldering iron, wire, etc etc?
1 Like
There’s a Maker Space close to me, they’ve everything, but it’s in Thailand, so bit of a language barrier.
So I found a video on YouTube, this is kind of what I’m looking to do, PC Box Fan - YouTube
But, I’d like it to be portable, with a rechargeable battery, and can also plug into the wall, DC right?
“It can be powered by your computer’s power supply, an AC adapter, or a 12 volt car battery”
I see the options as:
12V fans and power:
- 12v Fans: many to choose from on amazon. I did not find any for $1 as the article suggested. 80mm fans are common.
- Lead Acid Battery: motorcyle & childs toys 12V battery. $26 4ah 12V battery. Note: you could use lithium but the battery and charger are more $$$.
- Charger: any lead-acid battery charger will work. $16 12V battery charger
- RC power style connectors: $6 Bullet Connectors
5V fans and power:
- 5V fans: many to choose from on amazon. I did not find any for $1 as the article suggested. Seems 5V fans are generally smaller, largest I found was 40mm.
- Battery: use a power bank: many to choose from. $39 28000 mah battery bank
- Connectors from the fans to the power bank: $6 1ft USB Type-C Screw Terminal Block Connector, USB C to 5 pin Screw Termin
RC components
RC components include battery banks and chargers but these typically run at 7.2V. I did not explore this option but you could convert 7.2 up to 12vdc or down to 5vdc but I am not sure you gain a cost or performance improvement vs using 12V or 5V batteries.
Harder option, from scratch:
You could also build your own charger and battery bank using lithium batteries and charging modules but that is substantially more design.
The above 12 & 5vdc part choices are examples. You would need to choose the fans, voltage, and battery capacity to meet your application. You also may need other components like an on-off switch, wire, and connectors.
2 Likes
I’d use 12V fans.
I wouldn’t use lead-acid batteries; they have low cycle count in any case and cycle count goes way down with discharge beyond 50% even with deep cycle batteries. I would use a 12V-capable USB Power Delivery powerbank instead.
If you want to use USB-C Power Delivery, you can get USB-C PD “decoy boards” configured to ask for 12V and you just need a sufficient supply. It’s up to you to manage load. But 12V is possible for almost every USB-C PD “powerbank” — I’m not aware of any that can provide only 9V. These “decoy” adapters should be a few US dollars or equivalent. You can search, for example on aliexpress, for “usb-c pd decoy 12V”. Here’s an example from Amazon:
5A is a common limitation for the “decoy” boards. I would suggest choosing fans such that the set of fans you buy needs no more than 5A starting current (just multiply their rated starting current by the number of fans).
3 Likes
So, I’m looking at led light panels/blocks on Amazon. These can be powered by USB power…
For 6 to 8 fans, could you do the same?
Does anyone know what this component is called? I’ve tried googleing USB double male… but nothing. Cheers.
Also, is this magnetic option feasible?
Not sure I understand your question fully.
In the above thread we provided ways to USB power the fans?
1 Like
You only need two connections to provide power to the fans so I judge that magnetic connections would theoretically work.
Depending on the magnet material, the environment and amount of current you could have long term intermittent problems if the surface of the magnet is contaminated, corroded, oxidized etc. I also imagine soldering connecting to the magnets to be a challenge.
You could build a prototype and test just the connection schema.
Here is a reference to magnet connections to batteries to use as a starting point.
Where did the picture of the male=male connector come from and is used for?
LEDs draw far less current than fans. We keep saying you have to look at some actual fans. There is no answer that is generic for all fans. You have to find the actual power ratings on actual fans that you might use. They very substantially.
The more air flow you want, the more power you need. For this, you need to understand at least the basics of Ohm’s law:
The amount of airflow you are going to get is primarily proportional to the amount of power the fans consume. More watts = more airflow. Power (watts) in electricity is volts (V) times amps (A). So as a contrived example: if you have 5V fans that draw .2A that is 1W. Some motors are a little more efficient than others; some fan blades are more efficient than others, but you can’t do more than 1W of work with 5V at .2A.
You generally speaking can’t draw more than 1A from 5V on standard USB-A. (In the early days, it could be less than that, but I don’t remember seeing lower ratings recently.)
So 1A at 5V will do a max of 5W of work moving air.
Most of the USB-C PD decoy boards I’ve seen advertise 5A of capacity. 5A at 12V is 60W max capacity — 12 times more than 1A at 5V.
You can figure out how long you can run on battery by comparing actual consumption to capacity. 100 watt-hours would give you a theoretical max of 1 hour 40 minutes at 60W.
1 Like
Thanks guys, lots of great feedback. Once I get a prototype up and running I’ll report back!
1 Like