On one of the amateur radio sites I saw a circuit for charging portable Ni-Mn and Ni-Cd batteries with an operating voltage of 1.2-1.4 V from the USB port. With this device, you can charge portable rechargeable batteries with a current of approximately 100 mA. The scheme is simple. It will not be difficult to assemble it even for a beginner radio amateur.
Of course, you can buy ready-made memory. There are a lot of them on sale now and for every taste. But their price is unlikely to satisfy a novice radio amateur or someone who is able to make a charger with their own hands.
I decided to repeat this scheme, but to make a charger for charging two batteries at once. USB 2.0 output current is 500 mA. So you can safely connect two batteries. The finalized scheme looked like this.
I also wanted to be able to connect an external power supply with a voltage of 5 V.
The circuit contains only eight radio components.
From the tool you will need a minimum set of a radio amateur: a soldering iron, solder, flux, tester, tweezers, screwdrivers, a knife. Before soldering radio components, they must be checked for serviceability. For this we need a tester. Resistors are very easy to test. We measure their resistance and compare with the nominal value. There are many articles on the Internet about how to test a diode and an LED.
For the body I used a plastic case measuring 65 * 45 * 20 mm. The battery compartment was cut out of a Tetris children's toy.
I'll tell you more about the alteration of the battery compartment. The point is that initially
the pros and cons of the battery power terminals are set opposite. But I needed two insulated positive terminals in the upper part of the compartment, and one common negative terminal at the bottom. To do this, I moved the lower positive terminal up, and cut out the common negative terminal from tin, soldering the remaining springs.
As a flux when soldering springs, I used soldering acid in compliance with all safety regulations. The place of soldering must be washed in running water until complete removal traces of acid. I soldered the wires from the terminals and passed them through the drilled holes inside the case.
The battery compartment was fixed on the cover of the case with three small screws.
I sawed the board out of the old modulator game console"Dandy". Removed all unnecessary details and printed wiring tracks. Left only the power socket. I used thick copper wire as new tracks. I drilled holes in the bottom cover for ventilation.
The finished board sat tightly in the case, so I did not fix it.
After installing all the radio components in their places, we check the correct installation and clean the board from the flux.
Now let's unsolder the power cord and set the charging current for each battery.
I used a USB cable from an old one as a power cord. computer mouse and a piece of power wire with a plug from Dandy.
The power cord must be given special attention. In no case should you confuse "+" and "-". I have a “+” power plug connected to the center pin with a black wire with a white stripe. And the "-" power goes through the black (without a strip) wire to the outer contact of the plug. On the USB cable, "+" goes to the red wire and "-" to the black one. We solder plus with plus and minus with minus. We carefully isolate the places of soldering. Next, we check the cord for a short circuit by connecting the tester in resistance measurement mode to the plug terminals. The tester should show infinite resistance. Everything must be carefully double-checked, no matter what burns the USB port. If everything is fine, we connect our cord to the USB port and check the voltage on the plug. The tester should show 5 volts.
The last step in the setup is setting the charging current. To do this, we break the circuit of the VD1 diode and the "+" battery. In the gap we connect the tester in the mode of measuring the current turned on to the limit of 200 mA. Plus the tester for the diode, and minus for the battery.
We insert the battery into place, observing the polarity, and apply power. At the same time, the LED should light up. It indicates that the battery is connected. Further, by changing the resistance R1, we set the required charge current. In our case, it is approximately 100 mA. With a decrease in the resistance of the resistor R1, the charging current increases, and with an increase it decreases.
We do the same for the second battery. After that, we twist our body and
the charger is ready to use.
Because different AA batteries have different
capacity, it will take different time to charge these batteries. Batteries
with a capacity of 1400 mAh with a voltage of 1.2 V will need to be charged using this
circuits for approximately 14 hours, and 700 mAh batteries will take only 7 hours.
I have batteries with a capacity of 2700 mAh. But I didn’t want to charge them for 27 hours from a USB port. Therefore, I made a power socket for an external power supply of 5 volts 1A, which I had lying idle.
Here are some more photos of the finished device.
Stickers were drawn using FrontDesigner 3.0. Then printed to laser printer. I cut it out with scissors, pasted it with the front side on a thin adhesive tape 20 mm wide. Cut off excess tape. I used a glue stick as glue, after lubricating it with both the sticker and the place where it is glued. How reliable it is, I don't know yet.
Now the pros and cons of this scheme.
The advantage is that the circuit does not contain scarce and expensive parts and is assembled literally on the knee. It is also possible to power from the USB port, which is important for beginner radio amateurs. No need to puzzle over where to power the circuit. Despite the fact that the scheme is very simple, this way charging is used in many industrial chargers.
It is also possible, by slightly complicating the circuit, to implement switching of the charging current.
By selecting R1, R3 and R4, you can set the charging current for batteries of different capacities, thereby providing the recommended charging current for this battery, which is usually 0.1C (C-capacity of the battery).
Now the cons. The biggest one is the lack of stabilization of the charging current. That is
When the input voltage changes, the charging current will change. Also, if there is an error in the installation or a short circuit of the circuit, there is a high probability of burning the USB port.
Highly simple circuit USB charging for finger (AA) and little finger (AAA) nickel-metal hydride batteries. The circuit consists of only a few parts, which are very easy to find in some unnecessary electrical appliance or buy in a radio store.
Schematic diagram for AA charge from USB
List of device parts
- Pulse Diode 1N4007 - 2x
- Resistor 0.5W 9.7 ohm - 2x
- Resistor 0.25W 10 Ohm - 2x
- LED (any color) - 2x
- USB plug - 1x
The charging time of course depends on the current that we will supply to the batteries, as well as the capacity of the rechargeable batteries themselves. For example, Chinese batteries UltraFire with a real capacity of about 0.4-0.5 Ampere * hours, they charge me completely in 2-3 hours.
Naturally, this "charger", unlike the one, does not notify you of the end of the charge, so do not forget to follow the process, because overcharging can adversely affect Ni-MH batteries. And two miniature LEDs of any color serve as an indicator, they show whether the battery is charging or not. You can use surface mount LEDs (SMD) to reduce the size of the board.
The most convenient way is to solder the USB input directly onto the charging board, which will turn out to be very compact in size. Personally, my board dimensions turned out to be extremely small, namely: 2.8 x 1.5 cm.
The charging voltage is ~4.85V, the current depends on the resistance of the resistors used, with the indicated ratings up to about 160 mA.
I got a charging current of 141.2 mA.
I want to note that during prolonged charging, there is a slight heating of the resistors by 9.7 ohms, and in order to avoid this, take not 0.5 W resistors as indicated in the diagram, but 1 W or more.
In conclusion, I want to say that the quality of charging with such a device remains to be desired. But if you need to quickly assemble the circuit and charge the battery, then this is it.
I think that everyone had unpleasant moments - the phone was almost discharged, there were no outlets in the near future, or the lights were turned off, but you needed to call.
This is especially true for smartphones, which for the most part are very quickly discharged.
At first I wanted to buy something like a mechanical charger, but I accidentally stumbled upon this amazing thing.
USB charger for phone from 4xAA batteries Portable Charger.
Characteristics:
Charging type - 4 AA batteries
Output current: 0.5A
Voltage: 5V
Material: plastic
Black color
Size: 7.8x6.2x2.1 cm
This wonderful device is a plastic box with places for installing 4 AA batteries (or rechargeable batteries), with three LEDs and a USB connector. You can connect your phone or smartphone or any USB charging device to it using a USB cable.
At the end there is a switch with three modes - flashlight mode, off, and USB charging. When the phone is connected, it is set to USB mode and is being charged.
My experience of using: Smartphone Fly The 4404 was down to 35% battery and lasted 22 hours with this device!!! I was on a trip, there was no way to charge. I called, sent SMS, used mobile Internet and came home with the same 35%. Batteries (the cheapest ATB) had to be replaced once in 22 hours and after that they lasted a month for the flashlight to work.
Flashlight - 3 LEDs, shines brighter or dimmer depending on the degree of discharge of the batteries.
Actually, before the trip, I bought this device, knowing that in the call mode, mobile internet and SMS my Fly is able to hold out for 12 hours and that's all ... The test was a success, and I do not regret the purchase at all.
If you have a weak battery in your smartphone, often turn off the lights or you are often away from electricity - buy it, you won't regret it. Buy batteries in advance and you are in touch. e-book he is also quite capable of recharging.
You can install both 4 and 2 batteries. The only thing is that the body quickly got worn out from constant carrying in a purse.