Help with batterys!

[chase_gibson04]

Hello, I'm trying to take a pc fan and connect it to a rechargeable battery so that it can be used as a portable fan.

Any suggestions on batterys?

[anonvx]

Just get a usb battery power bank and a usb fan. Much easier. But if you really want to make one, it depends on voltage of fan. If 12v get 3 li-ion batteries and connect them in series. 

[chase_gibson04]

2 minutes ago, anonvx said:

Just get a usb battery power bank and a usb fan. Much easier. 

I wanna do it the harder way. I mainly want a battery that has 2 output wires and 1 input jack of some sort. Maybe dc? Dosent matter to me. And yes it is 12v.

Also I have heard that incorrectly drawing power from or charging a battery can be dangerous, is this an issue for my purposes?

 

[anonvx]

How big do you want it? How many cells? 

[chase_gibson04]

Just now, anonvx said:

How big do you want it? How many cells? 

Ok disclaimer: I have never done even a simple DIY project like this before. The fan is 120mm and the battery can be really any size. I was thinking of making a base for the fan that has the battery in it.

[anonvx]

okay, so your going to want to get something like this http://www.ebay.com/itm/DC-DC-150W-Boost-Converter-10V-32V-to-12V-35V-6A-Voltage-Step-Up-Power-Module-/263015704907?epid=933105838&hash=item3d3cf5294b:g:LMsAAOSwn-tZMMMD . Next your going to need one of these http://www.ebay.com/itm/Cigarette-Lighter-Socket-Splitter-12V-Dual-USB-Charger-Power-Adapter-Outlet-Car-/202022551668?epid=2121851657&hash=item2f097b8074:g:RvQAAOSwTJpZk7V2 and one of these http://www.ebay.com/itm/3S-20A-12-6V-Cell-18650-Li-ion-Lithium-Battery-Charger-BMS-Protection-PCB-Board-/192214883686?hash=item2cc0e65d66:g:J~IAAOSw1~JZPhvk

[anonvx]

I recommend just getting a 5v power bank and usb fan.

[chase_gibson04]

6 minutes ago, anonvx said:

*stuff I don't understand*

 

Ok could you please give a brief explanation of each part? How would these be connected to each other?

Is there a simpler way to go about this?

 

[mariushm]

Fans don't use a lot of power but they do need a voltage between let's say 6v and 12v to spin.  The lower the voltage, the slower they'll spin and naturally they'll be more silent.

 

So you could power them even from a single AA battery, as long as you use a circuit which raises the voltage from 1.2v .. 1.5v up to 6v .. 12v

The easiest would be to use a 9v battery and simply connect the fan's negative and positive wires to the battery and at 9v, the fan would spin fast enough. 

 

However, a 9v battery is more expensive and doesn't store a lot of energy so it's not quite the best solution.

 

The next easiest would be to use 2 AA batteries in a battery holder and a circuit to step-up ("boost") the voltage up to something between 6v and 12v.

 

eBay is full of such circuits (also called dc-dc converters , or BOOST regulators, or step-up regulators, because they boost voltage from a lower value to a higher value)

Since a fan usually consumes very little power, you don't need a very powerful step-up converter.

 

Here's a very cheap example of such a step-up regulator : http://www.ebay.com/itm/DC-DC-USB-2-24V-to-5-28V-2A-Boost-Step-Up-Adjustable-Regulator-Power-Module-/272682265912

 

 

You connect the wires from the battery holder (or the battery) on the input side (left) or you can use a usb cable with a microUSB connector on the end (for example if you have a battery bank around) and on the other side out comes higher voltage, depending on how much you twist that knob (the blue potentiometer in the center)

Before you connect the fan to this, you want to make sure the voltage coming out is not higher than 12v (you can do that with a multimeter)

 

Or, if you don't want to mess with adjusting voltage and you just want something to output 12v to the fan, you can use this equally cheap step-up regulator :  http://www.ebay.com/itm/DC-3-3V-3-7V-5V-6V-to-12V-Step-up-Power-Supply-Boost-Voltage-Regulator-Converter-/201919379310

 

 

This one works with any voltage between 3v and 6v, so you can't use it with 2 rechargeable AA batteries (because a rechargeable AA battery has 1.2v..1.35v) but it would work with 3 or 4 AA batteries or with 5v from a usb power bank. You could also use a 1860 lithium battery with it since such a battery has voltage between 3.7v and 4.2v

There's nothing to adjust, since the only voltage it outputs is 12v ... so you can connect the fan directly to those 2 pins and it will spin at the maximum rotation speed it can do.

 

For 1$ they're super cheap and easy to use. This plus 2 alkaline batteries (non rechargeable) would be cheaper than a single 9v battery and the two batteries will have more energy in them, will keep the fan working for longer time. And if you use rechargeable batteries it would be even cheaper in time, as you can recharge the batteries hundreds of times.

 

 

 

 

 

[Unimportant]

17 hours ago, chase_gibson04 said:

Hello, I'm trying to take a pc fan and connect it to a rechargeable battery so that it can be used as a portable fan.

Any suggestions on batterys?

I made one a few summers ago with a 12V high RPM server fan and 3 18650 cells, works fine and runs for hours, no special nonesense required (3 18650 battery holders would be nice tough). If you need a 18650 charger you can easely make your own el-cheapo unit based on a LM317 if you google around.