I am working on a special type of personal cooler for this summer (will be happy to show you the final product when I have a prototype).
One part of that cooler is obviously the air-mover
I am thinking to use a 120mm PC fan (decent CFM, quiet by design) that's connected to a USB-C supply (like a phone charger) but also has a battery if the user wants to take the cooler with them to a place without electricity.
It's seems to me like the only choice because the others require me to source and install the socket and housing, which adds to my lack of confidence
There's another one like it with housing for one battery, which I prefer, but it only does 5v. I guess two batteries are required for 12v?
I don't like that reviewers say that the design is flawed and an SMD resistor needs to be changed in order for it to charge...
Would appreciate any commentary about my parts selection... Maybe I am missing the point and can go for a 5v design? (reminder: a quality fan that moves a good amount of air at a very low noise and adjustability are important to my project)
PWM stands for Pulse Width Modulation, it's how you control the speed.
That UPS module may be ok or not, I only know there are a lot of wrong boards. I would look at Adafruit who I know have good boards.
NO 5+5 is not 12. You will either need two sets of batteries, or one with a buck converter or even better get a 5V fan.
Thanks for spending time to reply to me - I really appreciate it.
At this point, I think it's beneficial to add that I have some basic understanding of electronics.
I know what PWM is. Just wondering if I am oversubscribing to the idea that PWM's are more efficient (especially around lower RPM)
I know 5+5 is not 12. Actually I don't even understand why you might think I said anything like that?
A 18650 is typically around 3 - 4v. So, two 18650's will still have a boost converter.
What I was really asking is whether it is feasible (and therefore I can expect to find an off the shelf product) to boost to 12v from a single 18650.
As for 5v, wondering if the quality of those fans can match the 12v fan I mentioned? That one is really quiet and blows a nice amount of air.
I already have a loud AC fan, I am trying to build something better (to reiterate: I am not building a fan, the fan part is just one component of the system I am working on)
If you don't want to vary the fan speed, then you don't need PWM.
It's designed to control the speed of 4-pin PC fans, which is what your chosen fan is, so it should be.
Yes. Lower frequencies could cause an audible whine, and noise seems to be important to you. 25KHz is above the hearing range of almost all humans.
I'm not sure if using two of those other "UPS modules" would work or be safe, so go with the 12V version.
Alternatively look for separate battery holder, BMS module and 12V boost module. Make sure the BMS module has protection for both over-charging and over-discharging. Also that the boost module has sufficient current capacity for the fan, which may draw a much larger current when starting up.
Sometimes in prototyping, you have to take chance, it's what prototyping is all about.
As it's special, then that limits the amount and quality of the advice you can get.
Why not just get the parts and try it out?
If you want to use a single 3.7V 18650 and boost it to 12 it's life will be x. If you use two 3.7V 18650 in series the life will be 2x. Your choice.
I am done with this, good luck.
