Wednesday, March 16, 2011

Vortex Rechargeable Battery Pack Mark II

Assalamualaikum to all VE readers... it has been a while since we posted anything new, but I'll try to put up some old stuff, which is pretty simple but nevertheless provides a new perspective in DIY stuff.

So... I suppose you have read some of our older articles regarding rechargeable battery packs? Well this article is pretty similar conceptually, but with some major changes in reliability and structure. What I found out when I was using the older version is that, when one of the batteries conks out, it is pretty difficult to know which one is so, so you have to test them using LEDs, while fumbling through your prototype wiring and so on. This design is more rugged, stable, and takes safety into consideration, if the battery leaks or explodes, etc.

Let the graphics speak for themselves.


Here is the transition from raw batteries into being wired up (soldered of course), geared for testing & combination. So... Some notes to be taken:

1. In the bottom of the figure, both of the batteries in the left are Samsung batteries, and they have three and four terminals respectively. The way to know the right wiring is not only by testing it using a Digital Multimeter (DMM, check the highest voltage) but to also test using LEDs and see which combination produces the brightest intensity, because voltage itself doesn't mean it delivers the desired amount of current. Third is a Nokia battery, and fourth is a Sony Ericson.

2. Color Coding is very important (red: positive terminal, black: negative). When the whole thing is connected, you'll easily see from the color. Also, it is a good practice for all projects as well.

Quality Check

The next figure is the QC part. You'll see how two batteries are recharged on a breadboard. Explanation:
1. LED's off, meaning the battery's conked.
2. Now we'll recharge it for a few seconds....
3. LED's on. Battery is still functioning. Result: PASS
4. Sony Ericson battery's status: Charging....
5. LED's on. Battery is still functioning. Result: PASS

The image above is just to show how much voltage will it generate if all the batteries are connected. If you're afraid of combining different batteries together, read a reply to a my similar worry a few years ago. :)
Quote of the reply:

There's no problem of using batteries of varying capacities in series as long as each is delivering it's share of the power.

The problem occurs when the battery with the lowest capacity runs out of charge. Since the current is still flowing in the same direction (courtesy of all the other cells), it's effect is to place a reversed voltage across the dead cell. This could lead to the depleted cell either overheating or exploding.

Terminals of the batteries

Next, let us show how the terminals are derived. This may take some time, but Nokia handphones' sockets are rugged and doesn't leave room for misconnections due to polarity confusion i.e sometimes you insert the terminals incorrectly due to structural reasons. Some elaboration:

A. All sockets harvested from Nokia cellphones.
B. One of them looks like this, with a tape at the back. Remove the tape.
C. Now you can see the metal contacts clearly for halving. You might cut it wrongly, so observe the metal contact regions.
D. Clamp it using a small G-clamp (they're VERY useful)
E. Saw it (a hacksaw is also very useful)
I. Now you have extracted a socket, and you can bend the terminals for fitting it into a holed circuit board.
F. Another instance (from the ubiquitous 3310)
G. After being sawed....
H. Bend the terminals to reveal the metal contacts.
J. Solder them on a donut perfboard. I know this seems tedious, but believe me, The task of connections after that is a breeze, since you don't need to worry about the terminals anymore.

IMPORTANT: Make sure of the right terminals (positive/negative) are identified on the sockets' terminals by sticking a Nokia Charger into each socket, and check the polarity using a DMM or an LED.

Basic Structure

Now... The next step is to combine the rest. So... the figure above shows the combination done from 1 to 3. The boxes number 4 & 5 show the sockets being combined with the wiring (Hence the importance of color coding the wires).

Box No. 6 show the batteries being recharged. I used a Nokia 3310 Charger, which is very common in my house as an attic material.

Battery Tester Systems

Next, I wanted an off-board testing capability for the batteries, so I thought of using some old cellphone keypad boards which have pretty LEDs to it. They're very bright, and aesthetically good as well.

The figure above (You may want to click on it for a clearer view) tells:

a. A cellphone keypad board, which has SMT LEDs on it.
b. Just test the LEDs by connecting a supply to the terminals of the revealed LEDs. All of them are connected in parallel, so the rest of the LEDs should lighten up as well when you supply to only one of them
c & d: Screwed the LED board to the battery pack as a platform.
e. Another view of the unglued structure.
f. Epoxy glue comes into play.
g. Drying the structure under heat
h. Halved pen casing to cover the external wiring of the LED keypad circuit. A white female socket is used for the Battery Tester Pad.
i. Pressed using another G-clamp and glued.

Basic structure complete.

Male Socket Extraction.

Here, I have some male sockets from broken Nokia chargers and they'll be used to interface the battery to external devices. And:
A. Four different male sockets shown there, un-scalped except the second one from the left.
B. All male sockets harvested and stripped.
C & D: A plastic piece to act as a frame for the sockets
E. All wired up
F. Epoxy glue kicks in. (I like this stuff)
G. Completed part of the external male socket.

This looks easy, but it takes time also. So... take your time.

Lastly... The figure above shows the last part, which is the Interfacer circuit. The way I wanted my battery to be is that it has an on-board tester, so that when you connect it to a prototype, you can continually monitor the condition of the battery. Also, a common interfacing connection between the battery and other circuits are needed. Explained as follows:

i. Male socket soldered to a donut perfboard
ii. A plastic case, which fits the imagination.
iii. Cut it into half.
iv. Now some ingredients shown here: green LEDs salvaged from keyboards, switches from mice, and drilled plastic casing to emphasize on the DIY and Recycletronics scene. (Heh heh...)
v. Fitted them all together.
vi. The Epoxy Glue Guy being nosy again...
vii. Added 100 ohm resistors for each tester LEDs and extended the LED terminals using the wires.
viii. Everything on display again; note that anti-ripple capacitors are added on the board for steady supply, alongside the USB female sockets.
ix. A side view before enclosure.
x. All connections soldered, fused, clamped and glued together.
xi. All ready for testing.
xii. The interfacing circuit, which is very simple, but I just wanted to fill in the box there.
xiii. Testing... testing.... Yup everything's good.

The rest of the performance is demonstrated in the video here:



So... a pretty lengthy article for such a simple project. What I'm trying to explain here is that there are myriads of techniques that can be employed when constructing a prototype. This is only a blog of IDEAS. So hopefully some is provided as well. The theme of my project orbits around using only the stuff I have in my house, so that's why the components used seem restricted. Probably just my habit, but I just wanted to demonstrate that it doesn't take much money to get practical experience actually, because everything's around you. I spent no money on building this prototype, if you exclude the epoxy glue.

As a reminder to everyone and myself, don't spend too much time on satisfying our needs (like doing projects, working, relaxing, etc) . This article is only an expression of a hobby, and nothing more. There are lots of duties to be fulfilled to Allah Almighty, which should be our focus in our life. Hopefully after reading this article, we'll realize that in our hustle and bustle, we'll quickly spare more time to please Allah SWT, for the life in hereafter is Eternal, and life in this world is only transient. InsyaAllah Tuan!!!

Best Regards to UM's Electrical Engineering Graduates.

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