Introduction: Elveet. Kinetic Charger Powerbank
Once I was on a trip and I had a problem with recharging my gadgets. I traveled for a long time on the bus, did not have the opportunity to charge my phone and knew that I would soon be without communication.
So came the idea to create a kinetic charger, which will not depend on the power outlet.
If you need to recharge your gadget on a trip, hike, on the beach or in transport, then Elveet will help you. You can just shake Elveet or put it in your bag (backpack) and go to work (go hiking, to the beach, to the mountains, etc.). The device is charging when you are moving.
Elveet is a kinetic charger.
The principle of operation Elveet is based on the phenomenon of electromagnetic induction
Step 1: Component Parts of the Elveet
1. The Inductor consists of a 9-magnetic Halbach array and three coils.
2. PCB contains an inductor 200mA step-up-converter, a battery charger, and a battery step-up converter 5V 2A output.
3. The lithium-polymer battery 2800 mAh.
4. The case consists 4 parts and is made with 3D Printer.
The whole project is created in Fusion 360.
Step 2: Elveet Inductor
The inductor converts the kinetic energy of your movement into an electric current. The efficiency of the inductor is the most important parameter. The amount of accumulated energy in the internal battery depends on the efficiency of the inductor.
The inductor consists of three coils, a Halbach magnetic array, and three diode bridges.
The working field of the coil is the part above which the poles of the magnets pass, that is, the longer this part is, the more energy we can get.
Further, the outputs of each coil are connected to the diode bridge, that is, the coils are independent in voltage. And the current of all three coils is summed up after the diode bridges.
Diode bridges use Schottky diodes with very low forward voltage PMEG4010 produced by Nexperia. These are the best diodes for such applications and I do not recommend changing them to others.
The magnetic Halbach array concentrates the magnetic field on one side. On the other side, the magnetic field is very weak.
Halbach array requires almost double the number of permanent magnets but the efficiency of the Halbach assembly is very high.
The magnetic array passes over two parts of each coil and always the poles pass over different parts. Since the coils are electrically independent due to diode bridges, their influence on each other is excluded.
The inductor uses an assembly of 9 neodymium magnets 5X5X30mm N42. Two more magnets 2X4X30 N42 are used as springs.
The efficiency of the inductor depends on the rate of change of the magnetic field. For this, the path of the magnetic assembly is increased. Thus, the rate of change of the magnetic field is increased substantially due to the large acceleration of the magnetic assembly during motion.
This inductor is much more efficient than an inductor with a cylindrical magnet in the center of the coil. The cylindrical inductor has only the upper and lowers working part of the magnet. The middle part of the cylindrical magnet almost does not work in the current generation. Therefore, its efficiency is low.
The Elveet inductor has a 4-pole magnetic system which is directed strictly perpendicular to the wires of the coils.
After the diode bridges, the current of the coils is summed up and fed to the converter and charger board.
Step 3: Elveet PCB
The circuit and all components of the boards.
It contains three main parts:
1. Step-up 200mA converter inductor current. The chip NCP1402 is used.
It is a boost converter that operates from 0.8 volts and gives a fixed voltage of 5 volts and a current of up to 200 mA. The task of this chip is to provide a comfortable voltage for charging the battery.
2. Charge device chip STC4054
This chip receives 5 volts from the inductor or from an external source (via micro-USB) and charges a Lithium-polymer battery with a capacity of 2800 mA. The inductor current and the current from the external source are decoupled via Schottky diodes.
Also, the second pair of Schottky diodes allow Elveet to operate as an uninterrupted power supply, that is, you can charge Elveet and receive current from it for your devices at the same time.
3. Step-up output converter. It boosts the battery voltage to 5 Volts and provides a current of up to 2 Amperes to power the gadgets. In this case, the LM2623 chip is working.
A good feature of the LM2623 is an internal high-power transistor and an output current of up to 2 Amperes with low output voltage ripple. The output voltage is fed to a standard USB connector.
In addition to these parts, the board has a touch-sensitive load switch (for example a powerful traveling lamp or other constant loads). There are also output pins for connecting the wireless charger instead of the USB cable, but this option is designed for the future.
Step 4: Elveet Case
All parts of the case and the magnet holder are printed on a 3D printer.
All STL files are here.
18 - 54 - 133 мм (5, 24 - 2,13 - 0,728 in)
Step 5: Coils
On a rectangular base 5x35 mm high 8 mm, we reel coil with a wire of 32 AWG (0.2 mm).
The coils are made with a wire of 32 AWG (0.2mm) on a rectangular base. The number of turns is approximately 1200.The width of the entire coil should not be more than 20 mm. You can apply a thicker wire, but for a boost converter, this will be a heavier mode of operation. A thinner wire will give more voltage but the current will drop and ohmic losses will increase.
After winding all coils should be wrapped with PTFE tape.
Step 6: Board Diode Bridges
This is a narrow board for 12 diodes.
It is located next to the coils.
The outputs of each coil are connected to the bridges after the board is placed in the groove.
Step 7: Checking Connections
To do this, you need a thin board, which is mounted 10-15 white LEDs and one capacitor of approximately 2200 microfarads.
LEDs are connected in parallel and soldered to the board of diode bridges.
When moving the magnetic assembly over the coils, all the diodes should shine brightly.
Further, the test board is removed and the bridge board pins are connected to the converter board.
Step 8: Final Assembly
We connect the battery and inductor wires to the board.
After that, we collect the upper and lower covers of the device using two screws.
The device is ready to work.
Now you are completely energetically independent!
Good travel and good charge to your gadgets!
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