The moderator on the other website forum needed to close this same thread because this kid knows nothing about batteries.

At least on this forum, posting questions about things that you know nothing about is not a violation of the ToS/UA -- if anything, it's sorta the objective.

 

The moderator on the other website forum needed to close this same thread because this kid knows nothing about batteries.

Closing the thread will help the threads starter exactly how?

Ron

 

The problems you face come down to having 3 fans with each fan being a 3 volt 0.28 amp fan. So with the 3 fans in parallel you need a source power of 3 volts at 0.84 amp. Now in the interest of allowing some overhead on a battery supply I would just consider calling it 3 volts at 1.0 amp. In theory a 3 volt 1.0 amp hour battery would run your fans for about 1 hour but the reality is that a 3 volt 1 amp hour battery is not likely to provide that max battery rating for an hour. You may, for example, get 0.250 amp for four hours but I doubt the maximum for 1 hour or 2 amps for a half hour.

As has been pointed out there is no free ride. Things like buck, boost converters do work for their intended applications but when all is said and done you can't get something for nothing. Power is power and that is as good as it gets. If I want 1 amp at 3 volts I want 3 watts of power.

While coin cells are ideal for their applications they are not high current sources. Just for example this is a data sheet for a 2032 standard coin cell battery. Typical Capacity: 235 mAh (to 2.0 volts) so I doubt you would get even an hour for a single fan. Batteries are designed with a load in mind and your load(s) exceed what these batteries are designed for. You need to select or find a battery designed around your load requirements. You al;so want a battery not only capable of the load but intended application, for example is this a one time application where following a demonstration the batteries are trashed or do you want a battery source which is rechargeable?

An hour run time is one thing and 8 hours run time is another thing all together. The longer you want the power source to last, the more the power source gets larger and the more the cost increases. You can find for example 3.7 volt LiIon batteries in the 2,000 mAh range which are rechargeable and use 4 of them in parallel which would run your fans for 8.0 hours and if there is a concern with 3.7 volts a single simple 1N4000 series diode would get you down around 3 volts. Here is an example.

Ron

Ok, so in my situation maybe a 5 inch by 5inch solar cell might work the best right?

 

Closing the thread will help the threads starter exactly how?

Ron

The moderator on the other website forum needed to close this same thread because this kid knows nothing about batteries.

your right i dont know any thing about batteries/ electronics but im trying to learn and im not a kid. At one pointe in your life you didn't know either so please cut me some slack and let people who want to help me, help.ty

 

Ok, so in my situation maybe a 5 inch by 5inch solar cell might work the best right?

Do you have the datasheet for a 5”x5” solar cell? I don’t know which cell you’re thinking of, so I looked up a similar solar cell. It states that at the maximum power point, it outputs about 0.5V

That means that you would need at least six of these, to get 3V. You’d have to build a panel at lease 10”x15” and it would have to be in bright sunlight for 8 hours.

Does this seem realistic?

 

Ok, so in my situation maybe a 5 inch by 5inch solar cell might work the best right?

What is that based on?

You said that this was going to be for a presentation (of one hour, but then somehow that turned into eight hours at some point).

Is this presentation going to be indoors? Are the lights going to be on or off while making your presentation? Or is it going to be outdoors at noon on a bright, sunny day?

 

Do you have the datasheet for a 5”x5” solar cell? I don’t know which cell you’re thinking of, so I looked up a similar solar cell. It states that at the maximum power point, it outputs about 0.5V

That means that you would need at least six of these, to get 3V. You’d have to build a panel at lease 10”x15” and it would have to be in bright sunlight for 8 hours.

Does this seem realistic?

Provided that the cell can deliver the needed power (and my best estimate is that it is actually about the right size to do that in bright sunlight), then the voltage issue could be dealt with using a DC-DC converter.

 

Do you have the datasheet for a 5”x5” solar cell? I don’t know which cell you’re thinking of, so I looked up a similar solar cell. It states that at the maximum power point, it outputs about 0.5V

That means that you would need at least six of these, to get 3V. You’d have to build a panel at lease 10”x15” and it would have to be in bright sunlight for 8 hours.

Does this seem realistic?

Thank for your reply,

What is that based on?

You said that this was going to be for a presentation (of one hour, but then somehow that turned into eight hours at some point).

Is this presentation going to be indoors? Are the lights going to be on or off while making your presentation? Or is it going to be outdoors at noon on a bright, sunny day?

It was just a question, i did say i needed it for about 1hr presentation, then I thought what about 8 hrs. Sorry for the confusion.

 

You've asked a bunch of questions, but do you understand the answers?
Making random changes, like going from batteries to a 5 x 5 solar panel (is this presentation where there's sunlight, and where did that size come from?), or changing from 1 hour to 8 hours, leads me to believe you are not really thinking about what's required to arrive at a good solution.

A good solution needs firm requirements
So what exactly are the requirements for running the fans (location, duration, time between presentations, etc.)?

 

@crutschow is correct; one mistake a lot of beginners make is they move their requirements around as they try to figure things out. The result is you're trying to hit a moving target and things become very convoluted and difficult. If you want this project to be successful, first nail down exact specifications. i.e. I will be using 3 fans, all model number 123, the fans must run at abc speed for a minimum of xyz hours, I have H x W room for batteries and my budget is $x. Do the batteries have to be rechargeable? Now with this information we can help you design something specific. Maybe you build it and decide it needs changes, that's fine. But to build something you really need to nail down exactly what it must do before you begin.

 

Many posts on the other forum and 18 posts here resulted in him learning absolutely nuthin.
Isn't this the Chat section where we and our peers chat about fairly complex circuits?
I think learning the basics of electronics (Ohm's Law etc) belongs in school, not in this forum section.

 

Many posts on the other forum and 18 posts here resulted in him learning absolutely nuthin.
Isn't this the Chat section where we and our peers chat about fairly complex circuits?
I think learning the basics of electronics (Ohm's Law etc) belongs in school, not in this forum section.

Well, the name of the forum is "General Electronics Chat", not "Fairly Complex Circuits Chat".

 

We don't all have the luxury of taking classes at school.

 

I perceive a problem with the TS's approach. He is less interested in learning about how things work than he is in throwing magical technology at the problem that he doesn't understand. Now, this doesn't mean he can't or won't learn, but it does mean that he needs to be grounded (no pun intended) by the responses if people want to actually help him. He needs to be relentlessly brought back to the fundamental problems and answers he prefers to hand wave away, if people want to help him.

On the other hand, so far as I can tell, helping is not compulsory, nor is reading any particular thread, nor is even seeing the threads of a particular person. So, I am not sure what the controversy is here: help, watch, or just ignore. How is it a burden when you can ignore it?

This last is not a rhetorical question, I don't really understand why people can't just ignore.

 

Guys, guys, guys. This is nothing new. EVERY meeting I have with Marketing is like this. Some can be gently nudged, with a knowledge feather, into the realm of physics reality, others need to be be bludgeoned with a 1kW load bank to educate them. (THIS WILL NOT FIT IN A 1mm x 1mm HOUSING YOU DOLT <whack whack whack>)

TS: Listen to the grumpy old folks on here. They know what they are doing. If you want to a.) learn and b.) solve the problem. Give them the DETAILS they ask for and when they give responses, LEARN from those responses.

I get the feeling you might have made some promises (maybe to a VP or a CEO) that this can be done and those nasty engineers aren't giving you the answers you want. Which is it? Feather; 1kW load bank

 

Somewhere in this thread or on the other forum he said, "We must …" which implies a bunch of school kids doing an assignment.
Here he said, "I need to power three fans, I only need it to run for an hour for a presentation. The goal is to run it off a button cells. How can i make it last 8 hrs?"
He has been told that he needs a much larger battery but does not listen and believes in "a capasitor, risister, joule thief, or chip to BOOST the power from a tiny button cell." He does not believe that he needs lots of magic to do it.

 

He’s been silent for a while. His last post was ~5:00pm last night. I wonder if he’s in a different time zone? Waiting for twelve hours to see if he returns. Otherwise, the project may have been due today.

 

Do you have the datasheet for a 5”x5” solar cell? I don’t know which cell you’re thinking of, so I looked up a similar solar cell. It states that at the maximum power point, it outputs about 0.5V

That means that you would need at least six of these, to get 3V. You’d have to build a panel at lease 10”x15” and it would have to be in bright sunlight for 8 hours.

Does this seem realistic?

Thanks for your help, let me try this again with some more info. The 2 mini fans say they are 0.28 watts each at 3v and 1 fan at 3.7w and input volt at 8max. I need to use the smallest batery posible or solar cells. 1 fans wires positive/ negative is about 2mm thick and the other 2 fans wires positive/ negative is like 1/2 mm so thin. I hope i wrote it the right way lol. thank you

 

Thanks for your help, let me try this again with some more info. The 2 mini fans say they are 0.28 watts each at 3v and 1 fan at 3.7w and input volt at 8max. I need to use the smallest batery posible or solar cells. 1 fans wires positive/ negative is about 2mm thick and the other 2 fans wires positive/ negative is like 1/2 mm so thin. I hope i wrote it the right way lol. thank you

What is it you are doing with these fans?

What is the actual goal of your project? What purpose is the project trying to accomplish?

Leaving that aside for now, the information you are giving now is a bit different than what you gave originally in terms of the fan specs. Originally you said that the fans were 3 V, 0.28 amp fans. Now you are saying they are 0.28 W fans. Since you appear to be reading the latest directly from the fans, I'll assume this is the correct info. This is a big difference. 0.28 amps means that it draws (under some specified load) 0.28 A of current which, at 3 V, means that it is consuming about 0.84 W of power, since power is the product of the voltage across a device and the current through it. But if it is rated to draw 0.28 W at 3 V, that means that the current draw is only about 93 mA, or just one-third of what it did before.

The third fan is more problematic. Under its spec'ed load it should draw about 3.7 W /8 V = 0.46 A, but that's at 8 V. I don't know how well it will work, or what it will draw, if you only apply 3 V to it.

Do you actually have these fans?

Can you connect them up to two batteries in series (preferably two AA cells or larger) and see if they will do what you need them to do powered that way? If the answer is yes, then we can proceed. If the answer is no, then we need to take a step back and look at a fundamentally different approach.

 

0.28 watts and 0.28 amps are entirely different. Lets break this down one piece at a time and see if we can get a solid specification.

0.28 watts at 3volts DC is only about 0.09 amp, or 90mA. Using some rough estimation, the larger fan being 3.7w at 8v is probably around 1.4watt at 3v, which will require about 0.46A, or 460mA. So assuming you will run all 3 fans at 3v, your power source needs to deliver 643mA at 3V for some period of time.

Next two questions, and they need specific answers, not estimations.
(1) How long do they need to run for between battery changes?
(2) How much room is there for batteries (an exact measurement)?