LiPo Battery 11.1v with a mosfet at 4.0v output?

[DaMulta]

Anyone know of a mosfet that could do this?

11.1v 3300 Mah King Arms Lipo Lithium Polymer Airsoft Battery | Lipo | Airsoft Batteries | Airsoft Batteries, BB's, Gas & Chargers | Airsoft Outlet Northwest


Was thinking about doing this to a passthough for a Titan. Kind of a homemade screwdriver BUT the battery would not be right in front of your face. KIND of safer in a ways......

I bet knocking the voltage down, along with the right amps this baby would run for days LOL.

WHICH would be a good thing!!!!!

 

[kinabaloo]

The short suggestion is to find another battery, with a voltage no greater than 6 or at most 7volts.

Yes, you can do it (use a suitable voltage regulator and heatsink) but it would be so wasteful, even though it would last a long time (maybe 3 days).

Find a similar size unit (or smaller) at say 5v and then you'll be really happy with the result. Smaller voltage should provide higher capacity for similar physical size (and a lot less heat).

Also: higher capacity batteries are not necessarily designed for high output current, so always check that (or suggested uses).

The kind of 'ultimate' batteries that might be suitable, if the voltage is not too high, would be used for applications such as (small scale) robotics servos (motors). If you don't mind the size, there might well be suitable batteries out there.

The ideal compromise, currently, between physical size and capacity/power output capability is either the 14500 (high output current version) or mobile/camera batteries (for flat shape); and those that are of similar spec (500mAh - 2000 mAh that can output at least 1A).

The ideal does depend somewhat on which atty.

 

[wegster]

@kinabaloo - it seems based on atty resistance and voltage supplied, an atty 'wants' to use over 1A (which any of the 'bigger batteries' can feed. Does resistance increase much or something change that makes as low as 500mAh suitable?
I guess the real Q being - given a reliable (able to output several Amps max throughput, over time) power supply, what's the current being seen on a real atty?

 

[kinabaloo]

@kinabaloo - it seems based on atty resistance and voltage supplied, an atty 'wants' to use over 1A (which any of the 'bigger batteries' can feed. Does resistance increase much or something change that makes as low as 500mAh suitable?
I guess the real Q being - given a reliable (able to output several Amps max throughput, over time) power supply, what's the current being seen on a real atty?

Capacity (mAh, how much it has to give) and maximum current capability (how fast it can give it) can be very different things.

Avoid 'speciality' / backup type batteries; these have a high capacity but low maximum current (they have a high internal resistance). Some (a few) marked 14500s are of this unsuitable type.

Most attys will (try to) draw a bit more than 1A; but 1A will work reasonably well.

Speciality/backup batteries aside, the max current will generally increase with increased capacity; i.e. increased performance - but the 14500 is about the optimum compromise; one would not gain much in performance by going even higher in capacity (but still gain in how long the battery lasts between charges); but at the expense of increased size.

A cigar (or 6v Magnum) might draw 2A, but most ecigs will draw between 1 and 1 1/2 A.
Cigar designs try to up the juice flow too. Without that, it would be like putting a Ferrari engine into a Renault Clio; not upgrading the brakes and tires etc (analogy wearing thin ...) Might work without tears with more pit-stops (more topping up) ...

 

[DaMulta]

With the right mosfet you can reduce the voltage and amps down to what every you wanted tho. I was just thinking that a pack could be made with a battery like this and a retractable cord with a place to put a whole titan in would be the Ultra ScrewDriver PCC unit. Without the fear of it blowing up in your face.

I don't see why it would be so wast full if it would last 3 days or so.

MOSFETs - Single | Newark.com

I have no idea which one it would be.

The battery above should be 20 amp and about 25amp burst.


This battery shown above is used for high out put usage.

 

[DaMulta]

Capacity (mAh) and maximum current capability can be very different things.

Avoid 'speciality' / backup type batteries; these have a high capacity but low maximum current (they have a high internal resistance). Some (a few) marked 14500s are of this unsuitable type.

But drawing only part of it should increase mAh ratting right? Or am I wrong about that>?

 

[kinabaloo]

But drawing only part of it should increase mAh ratting right? Or am I wrong about that>?

Roughly, you would get the performance and life as if it was a 4v battery pack. But a 4v battery back would/could either be smaller or higher capacity (last longer). Hence I would search some more ...

 

[kinabaloo]

One would use a higher voltage (say 2x 3v) because it is just about ok and fits the lovely casing; or becuase you will use a voltage regulator (that works by adjusting the current) to provide a period of constant performance.

 

[DaMulta]

Roughly, you would get the performance and life as if it was a 4v battery pack. But a 4v battery back would/could either be smaller or higher capacity (last longer). Hence I would search some more ...

Well if you would get the same performace life as it would be at 11v downgraded to 4v I would have to say that kills my idea.

i just thought the life would be rated different if you knocked down the voltage.

 

[kinabaloo]

Well if you would get the same performace life as it would be at 11v downgraded to 4v I would have to say that kills my idea.

i just thought the life would be rated different if you knocked down the voltage.

Let's say the atty drew 1A. If the mAh is 3500mAh then it would last, at best, 3.5 hours. That's aan ideal that doesn't quite work out in practice but I could see it lasting 3 days of vaping. It's just that a lower voltage pack would be better.

In other words, it would last about the same time as a 4v 3500mAh battery back; but get a lot warmer in the process.

 

[DaMulta]

Is 1a what I should shoot for along with 4v for the Titan?

 

[kinabaloo]

Lets say the battery pack is 12v rather than 11v, to keep the math simpler - i.e. 3x 4v. So let's do away with the regulator and connect up 3 attys in series; each will have 4v across it. But you are inhaling from only one of them.

 

[kinabaloo]

Is 1a what I should shoot for along with 4v for the Titan?

The current just depends on the atty resistance and the voltage you apply. A voltage of aroun 4-4 1/2 is ideal. To be sure of peak performance the battery pack should be able to output 2A, but 1A is ok (will not be such a big hitter but will last longer); though a battery that can output the higher current is probably a higher capacity one.

 

[kinabaloo]

Think of a battery as a water tank. The voltage is the height of the water tank (actually the height of the water remaining in the tank). The capcisty is the volume of the tank. The maximum output current is the size of the outlet pipe at the bottom of the tank. The current is the water flow (volume) out of the tank. This depends on the width of pipes connected to the tank. But no use to connect a big pipe to a small pipe and expect a big flow ...

Hope this makes some sense

It's only an analogy and so not perfect. Perhaps it would be better to say that the voltage is like a pump; at least then the water can end up back in the tank!

Oh, chardonnay is discharged. Goodnight.

 

[caesar]

Sorry to bump in.

To make that pack work (11V and 3.3Ah) efficiently you would need a step-down voltage regulator. If designed properly you can get around 80% efficiency.

The math is simple: 11V 3.3Ah pack is 36.3Watt stepping it down to 4V for example will be equal to a 4V 9.075Ah battery without any losses in the step-down regulator.

Then you must tailor for the losses and 80% of the resulting pack is around 4V 7.26A and it should last for ~ 7hours of continous atty usage (non-stop) at a current draw of 1A.
Taking into consideration that you don't keep it always on, rather a 10sec puff then pause, you can do the math considering your vaporing habits.

 

[DaMulta]

Sorry to bump in.

To make that pack work (11V and 3.3Ah) efficiently you would need a step-down voltage regulator. If designed properly you can get around 80% efficiency.

The math is simple: 11V 3.3Ah pack is 36.3Watt stepping it down to 4V for example will be equal to a 4V 9.075Ah battery without any losses in the step-down regulator.

Then you must tailor for the losses and 80% of the resulting pack is around 4V 7.26A and it should last for ~ 7hours of continous atty usage (non-stop) at a current draw of 1A.
Taking into consideration that you don't keep it always on, rather a 10sec puff then pause, you can do the math considering your vaporing habits.

So I was right about using a larger battery like I posted then for longer power usage?

7 hours would be the ultra alright! At least chain smoking. I could see this being great for taking long trips while camping and other actives where you are not around any power source.

 

[caesar]

So I was right about using a larger battery like I posted then for longer power usage?

7 hours would be the ultra alright! At least chain smoking. I could see this being great for taking long trips while camping and other actives where you are not around any power source.

You were right.

7 hours continuous! That should make a few days of normal vaping.

The key piece is the step-down regulator, you can get already built quality ones pretty cheap too.

This one fits the example perfectly: DealExtreme: $9.27 Hobbywing 5V/6V 3A Switch-Mode Ultimate BEC (UBEC)
It's good for 3A constant and withstands 5A temporarily, insane power.
At 1A, 2A tops needed for an atty it's perfect. You can even select 5V or 6V output.

I myself use one in the car to accomodate different USB gadgets.

 

[DaMulta]

So you don't think that would be to much for the Titan? Don't think that would fry it LOL.

Wonder if I could find one that would switch from 3/4 with 2 Amp output.

Well wait your saying to use this with the USB passthough. LOL. Ok then yea it should be A OK. Maybe a mosfet at this voltage would be easier to step down so you would not have to have the USB passthough at all. Hmmmm

I kept thinking this does not seem right LOL cutting the voltage should increase the life span. Pulling the Amps, and Voltage


Also that one is (2-5 cells lithium battery pack ) Hmm wonder which one this is. There are lots of different ones.

 

[500KV]

You were right.

7 hours continuous! That should make a few days of normal vaping.

The key piece is the step-down regulator, you can get already built quality ones pretty cheap too.

This one fits the example perfectly: DealExtreme: $9.27 Hobbywing 5V/6V 3A Switch-Mode Ultimate BEC (UBEC)
It's good for 3A constant and withstands 5A temporarily, insane power.
At 1A, 2A tops needed for an atty it's perfect. You can even select 5V or 6V output.



I myself use one in the car to accomodate different USB gadgets.

That's a great find caesar.
And cheap enough to just order a spare at the same time.

 

[kinabaloo]

You were right.

7 hours continuous! That should make a few days of normal vaping.

The key piece is the step-down regulator, you can get already built quality ones pretty cheap too.

This one fits the example perfectly: DealExtreme: $9.27 Hobbywing 5V/6V 3A Switch-Mode Ultimate BEC (UBEC)
It's good for 3A constant and withstands 5A temporarily, insane power.
At 1A, 2A tops needed for an atty it's perfect. You can even select 5V or 6V output.

I myself use one in the car to accomodate different USB gadgets.

Yes, a good find. Some cost and size, but will be pretty efficient.

PWM to a large capacitor; monitor voltage to adjust pulse width. So a voltage controllable duty cycle oscillator, big capacitor, opamp and a MOSFET would do the trick. But would be far easier to use a ready-made unit.