Most people look in Google for the Minty Boost that boosts two AA battery cells (2.4V to 3.2V) to 5V. But it uses a Maxim or Linear Technology IC that you might not find in your country.

 

If you are determined to build this thing, you will have to do a good bit of research on it yourself, as I have no idea as to what components are available to you.

Here is a link to Ronald Dekker's "Flyback Converter for Dummies" page:
http://www.dos4ever.com/flyback/flyback.html

You will need to build a flyback-type converter, but you will need for it to boost only to 5v. The difficult part will be building the transformer, which you will have to do on your own, and you might have to do a good bit of searching to locate an N-channel power MOSFET capable of Id>=2A that has a very low threshold voltage. The BUZxxx MOSFETs that Ronald used won't work on <3V for the gate.

You will have to use a CMOS 555. You will need an oscilloscope. You will need to do a lot of experimenting.

 

I have a limited IC knowledge but why not use 4 AA battery cells (6V) and bring it down to 5V using some kind of current limit (resistor or circuit)

 

Using 5V to charge a Lithium battery will cause it to catch on fire.
He also needs a Lithium battery charger IC but they are also probably not available in his country.

Besides, 4 AA battery cells (6V when new) will quickly drop down to 5V and much lower all by themselves.

 

Here's a good post about a USB charger that boosts 3V to 5V. http://www.ladyada.net/make/mintyboost/

Aren't there a lot of battery charging IC's out there that should be used for LIon, LIpo batteries?

 

Many ICs are not available in The Philippines.
So he must make a discrete voltage stepup circuit and battery charger like we did 20 or 30 years ago.

 

Thank you everyone for your reply I really appreciate it.
I really need to seek for proper discrete component to boost 3V to 5V. I will use 555 as the 0sc. But I don't know what will be the value of the transistor? As well as the inductor?
What will be the factors to be considered in choosing these components to serves my purpose?
Thank you.

 

Click the link to Ronald Dekker's page. It will answer a lot of questions.

However, you will need to research what N-channel power MOSFET can you get from your suppliers that has a very low threshold voltage.

Like I said before, I have no idea what suppliers you have access to where you are.

 

Many ICs are not available in The Philippines.
So he must make a discrete voltage stepup circuit and battery charger like we did 20 or 30 years ago.

Sir, you are right that I need a discrete voltage step-up circuit.
But did you still remember the discrete voltage step-up circuit that you did
20 or 30 years ago?
Can you attached it here?
If not can you design again using only discrete component?
Thank you.

 

Hello,

Did you see this post on a philipinian forum?
http://www.electronicslab.ph/forum/index.php/topic,2665.0.html

It is about a boost converter using transistors.


Greetings,
Bertus

 

I was also going to suggest that he look at www.electronicslab.ph .

I hope he posts a video showing his Lithium batteries catching on fire.

 

Hello,

Did you see this post on a philipinian forum?
http://www.electronicslab.ph/forum/index.php/topic,2665.0.html

It is about a boost converter using transistors.


Greetings,
Bertus

A pleasant day to y0u sir

Its been a long time right?
Regarding the schematic you'd post from the Philippinians forum, it really helps me a lot. I really appreciate your help.
But I was wondering about the polarity of T1? I know that I need to custom made it but in that forum it did not said how to construct it. It only saidt that it has a 18Turns. I tried to post a question in that forum but nobody know who is the original author to contact with.
Basically, T1 is divided into two (2) windings righ?
The MAIN winding and the FEEDBACK winding.

What do you think is the direction of turns of the MAIN winding? Clockwise? or counter-clockwise? How about the Feedback winding?

Thank you.

 

Hello juan,

There are small dots near the transformet show the start of the windings.
I enlarged the shematic with comments.

Greetings,
Bertus

 

I was also going to suggest that he look at www.electronicslab.ph .

I hope he posts a video showing his Lithium batteries catching on fire.

Greetings,
Thank you sir for your precautinary concern.
But I won't charge Lithium battery which is very dangerous,flamable and unstable.
I will charge Lithium-ion instead.
Lithium-ion is far more stable than a Lithium battery in terms of recharging.
(accdg. to Battery University)

 

Hello juan,

There are small dots near the transformet show the start of the windings.
I enlarged the shematic with comments.

Greetings,
Bertus

Hi Bertus,
Good evening here. . . Good Morning there

Regarding the post, the start of the turn is indicated by a dot.
How about the other coil that is lower one?
It must be the coit is turn in the same direction?
The wire should be a magnetic wire? Which gauge do you think is applicable for 800mA?

Thank you.

 

Hello,

The start of the turns are on the right side for both coils.
I think AWG 22 wire will work.
http://www.hardwarebook.info/AWG
You can use enamel wire on a toroid.

Greetings,
Bertus

 

The voltage stepup circuit will have an output voltage of 5.8V. The absolute maximum charging voltage for a Lithium-Ion battery cell is only 4.2V. Nothing will limit the current.
When the battery becomes over-charged by voltage or current then it will catch on fire.

 

The voltage stepup circuit will have an output voltage of 5.8V. The absolute maximum charging voltage for a Lithium-Ion battery cell is only 4.2V. Nothing will limit the current.
When the battery becomes over-charged by voltage or current then it will catch on fire.

Greetings,
0k. That is right there is no voltage or current limiting circuit. Can we add a limiting ckt.? That is can cut0ff the supply to the battery (being charge) when it is full. Some kind a "automatic charging"?
What will be the added ckt. needed to obtain this purpose?

Thank you.

 

We use a battery charger IC. Maybe somebody can remember what we did 20 or 30 years ago. You are in a time warp.

 

We use a battery charger IC. Maybe somebody can remember what we did 20 or 30 years ago. You are in a time warp.

0k charger IC is more advisable to recharge battery. But based on your knowledge how can this ckt. can automatically adjust its 0pt current depending to its load? Thank you.