Money 

Charger nickel cadmium batteries by hand. A simple charger for nickel-cadmium batteries. General charging rules

S. Rychikhin

I suggest the option of a simple charger. To assemble it, you can use parts from old domestic equipment.

The device is an adjustable, stabilized current source that allows you to maintain a given value of the charging current throughout the entire battery charging process. The device diagram is shown in Fig. 1.

The mains voltage lowers transformer T1, rectifies the diode bridge VD1 and smoothes capacitor C1. The rectified and smoothed voltage is supplied to a current stabilizer assembled on transistors VT1, VT2, zener diode VD2 and resistors R2-R6.

The principle of operation of the current stabilizer is very simple: a conventional voltage stabilizer is assembled on transistor VT1, the base of which is supplied with a reference voltage from the zener diode VD2, and resistors R4-R6 are included in the emitter circuit, which set the battery charging current. Since the voltage at the base of transistor VT1, and therefore at these resistors, is stabilized, the current flowing through them and the emitter-collector section of transistor VT1 is stable. Consequently, the base current of transistor VT2, which regulates charging current batteries. Resistors R5 and R6 carry out coarse and fine adjustments of the charging current, respectively. The charging current is controlled according to the readings of the PA1 milliammeter. Diode VD3 prevents the connected batteries from discharging when the device is turned off. The HL1 LED indicates that the charger is connected to the network.

In the device, instead of those indicated in the diagram, you can use any transistors of the KT315 (VT1), KT814, KT816 (VT2) series. It is advisable to install transistor VT2 on a small heat sink with an area of ​​8... 10 cm2. The permissible forward current of diodes VD1 and VD3 must be no less than the maximum battery charging current. Zener diode VD2 - any for a voltage of 10...12 V. Fixed resistors - MLT-0.5, variable - any. Capacitor C1 - any oxide, with a capacity not less than indicated in the diagram and rated voltage not less than the amplitude value of the voltage on the secondary winding of transformer T1.

Transformer - frame scan output transformer of TVK-70L2 tube TV. Its magnetic circuit must be reassembled end-to-end by removing the paper insulating gasket in the gap between the ends of the magnetic circuit plates. Primary winding remains, but the secondary one needs to be rewound. The primary winding contains 3000 turns of PEV-1 wire with a diameter of 0.12 mm, the secondary (rewind) winding contains 330 turns of PEV-2 wire with a diameter of 0.23 mm. The cross-section of the magnetic circuit is 18x23 mm. The voltage on the secondary winding of the modified transformer should be within 22...25 V. DC milliammeter - any with a total deviation current of 50 mA.

All parts of the charger, with the exception of transformer T1, LED HL1, variable resistors R5 and R6, milliammeter PA1 and control transistor VT2, are assembled on printed circuit board, the drawing of which is shown in Fig. 2.

Appearance The assembled device is shown in Fig. 3.


The charging algorithm is very simple: discharged batteries are connected to a charger and charged for 16 hours. The charging current is selected based on the nominal capacity of the battery. To do this, the battery capacity (in Ah) is multiplied by 100 and the charging current is obtained in milliamps. For example, for a TsNK-0.45 battery the charging current is 45 mA, and for a 7D-0.125 battery it is 12.5 mA.

An error-free assembled device does not need adjustment.
[email protected]

On the Internet, I came across a circuit for an automatic Ni-Cd battery charger developed by Yuri Bashkatov. I assembled the circuit on a breadboard - it doesn't work. I modeled it on a computer using the Work Bench program. The result is what is shown in the diagram. The device is working in the following way. Transistor VT1 (p-n-p) is open if there is a negative potential at its base, which can appear when transistor VT2 (n-p-n) is open - this, in turn, happens if the potential at its base, set using variable resistor R4, is 0.3 - 0.4 V more than this indicator on its own emitter.

The emitter of transistor VT2 is connected to the cathode of thyristor VS1 and a rechargeable battery. As soon as the voltage across it reaches the threshold value, transistor VT2 will close. Following it, transistor VT1 will also close. The thyristor will turn off and the charging will stop. This prevents the Ni-Cd battery from overcharging.

Resistor R4 sets the operating threshold of the automatic device. To provide information about the voltage value at the base (the limit value of the charge voltage), you could connect a voltmeter to the base. However, the authors considered that it would be better to connect a voltmeter to the emitter of transistor VT2. Thus, immediately when connecting the batteries you can see what voltage is on them. With the button pressed, monitoring the voltage with a voltmeter, we set the voltage on the emitter using resistor R7. After that, without releasing the SA1 button, we set the device’s response threshold with resistor R4, monitoring the response when the ballast lamp EL1 lights up. We release the button, the light should be on, the batteries have begun to charge. As soon as the voltage on the batteries reaches the threshold mode, the light will go out and the charge will end.

The practice of charging Ni-Cd batteries has shown that the final voltage recommended in the instructions is not 1.2 V, or even 1.5 V, but 1.7 V, so for two batteries I set the response threshold to 3.4 V.


There is often no need to design complex devices that take into account many parameters of the discharge-charge cycle of batteries. It is enough to take into account a couple of parameters such as end-of-discharge voltage, end-of-charging voltage and charging current. Selected cycle parameters prevent overcharging or undercharging of batteries, which subsequently increases their service life.

The device is powered from an unstabilized source with an output current of at least 100 mA, the voltage of which, taking into account ripple, must be within 11.5...30 V.

Scheme:


The DA1 chip stabilizes the 9 V supply voltage for the remaining components of the device. The basis of the device is a Schmitt trigger on transistors VT1 and VT2, the latter of which is connected as an emitter follower. The hysteresis loop is stable over time and is quite easy to adjust. The SZ capacitor protects the Schmitt trigger from false switching when exposed to noise.
The state of the Schmitt trigger depends on the voltage of the charging battery connected to the output of the device. At a voltage of 4 V or less, VT2 is installed on the emitter of transistor high level voltage, and at 5.92 V or more - low. The low level of the output voltage at the emitter VT2 is not zero and amounts to 0.3 V, therefore, to eliminate the influence of the load on the lower switching threshold of the Schmitt trigger, decoupling diodes VD1 and VD2 are used, which do not open at this voltage.
Transistor VT3 operates in key mode and controls the charging current stabilizer on transistor VT4, LED HL1 and resistor R11. The HL1 LED is used as a stabistor and charging mode indicator. The charging current is set by selecting resistor R11. Thanks to double voltage stabilization (chip DA1 and LED HL1), the stability of the collector current of transistor VT4 is quite high (it did not change when connected to the output of a battery consisting of two to five cells of varying discharge during tests). The VD4 diode prevents the battery from discharging through the current stabilizer after turning off the power to the device.
Through transistor VT5, also operating in key mode, and resistor R13, the battery is discharged until the thyristor VS1 is closed. After opening the SCR VS1, the discharge stops and the HL2 LED, the discharge mode indicator, goes out.

Device operation:
First, a battery of four batteries is connected to the charger and then the supply voltage is applied. While the battery voltage exceeds 4 V (on average 1 V per cell), transistor VT1 is open, transistors VT2-VT4, diodes VD1-VD4 and thyristor VS1 are closed. Transistor VT5 is open and saturated, through it and resistor R13 the battery is discharged. HL2 LED is on. The discharge current should not be set to more than 1/10 of the battery capacity.

When the battery voltage drops below 4 V during discharge, the Schmitt trigger will switch, transistor VT1 will close, and VT2 will open. The output of the Schmitt trigger will set to a high voltage (about 8 V). Diode VD1 and thyristor VS1 open, as a result of which diode VD3 opens, transistor VT5 closes, LED HL2 goes out, and the discharge mode stops. At the same time, the high-level voltage from the output of the Schmitt trigger will open diode VD2 and transistor VT3, as a result of which LED HL1 will light up, transistor VT4 and diode VD4 will open, through which the battery will begin charging with a stable current.
By pressing the SB1 button, the device forcibly switches from discharging mode to charging mode. This is necessary if Ni-MH batteries are used, which are not subject to the “memory effect” and, accordingly, do not need to be pre-discharged.

During charging, when the battery voltage reaches 5.92 V (average 1.48 V per cell), the Schmitt trigger will switch: transistor VT1 will open and VT2 will close. Diode VD2 and transistor VT3 will close, LED HL1 will go out, as a result of which transistor VT4 and diode VD4 will close, and the charging process will stop. But the thyristor VS1 remains open, so the transistor VT5 will not open and the discharge mode will not turn on. After turning off the power of the device, you must disconnect the battery from it, otherwise it will be discharged.

Installation and components:
Transistors KT315B (VT1-VT3) can be replaced with transistors KT315G or KT315E. Other silicon low-power transistors can be used n-p-n structures with a maximum collector current of at least 100 mA, but for a Schmitt trigger it is advisable to select transistors with a base current transfer coefficient of at least 50. Transistors VT4 and VT5 - any of the KT814, KT816 series. They are mounted on heat sinks made of strips of soft aluminum measuring 28x8 mm and 1 mm thick, bent in the shape of the letter "U". Diodes - any low-power silicon, except VD4, which must withstand the charging current. Trimmer resistors R2 and R5 are multi-turn SP5-2. It is advisable to use LEDs HL1 and HL2 different color glow to clearly indicate the operating mode of the device.

Setting:
To set up the device, you need an auxiliary battery of 9... 12 V, to which a variable resistor with a resistance of several kOhms is connected by a potentiometer. To make it easier to accurately set the required voltage in the open circuit of one of the extreme terminals of this resistor, it is advisable to include another variable resistor with ten times less resistance as a rheostat.

The engines of trimming resistors R2 and R5 are set to the lowest position according to the diagram. Temporarily break the connection of the left resistor R1 according to the output circuit with the positive output of the device. During setup, this output becomes the input of the device, which is connected to the variable resistor motor. The negative terminal of the auxiliary battery is connected to the common wire of the device. The battery being charged is not connected to the output. After turning on the power, you need to make sure that there is a stable voltage of 9 V at the output of the DA1 chip.

Then the switching thresholds are set. A voltmeter is connected to the emitter of transistor VT2. First, the lower switching threshold is set to 4 V using the trimmer resistor R2. input voltage Below this threshold, transistor VT1 should close by 0.05...0.1 V and a high voltage level should be established at the emitter of transistor VT2. Then, using the slider of the trimming resistor R5, the upper switching threshold is set to 5.92 V. When the input voltage increases above this threshold by 0.05...0.1 V, transistor VT2 should open and set low level voltage at the emitter of transistor VT2. Check both switching thresholds.

Next, check that after transistor VT2 opens, thyristor VS1 also opens. If this is not the case, reduce the resistance of resistor R6, achieving clear opening of the SCR. To turn off the thyristor, the supply voltage is briefly turned off.

Finally, a series-connected milliammeter and a rechargeable battery are connected to the output of the device. In charging mode, select resistor R9 to set the desired brightness of LED HL1, and select resistor R11 to set the required charging current. Next, disconnect the auxiliary battery and restore the connection of the left resistor R1 according to the output circuit with the positive output of the device. SCR VS1 is turned off. The multimeter is connected to the output of the device in voltage measurement mode. Observe the process of charging the battery and automatically switching the device to the discharge mode after reaching the output voltage of 5.92 V. Next, in the discharge mode, resistor R12 sets the brightness of the LED HL2 and the initial discharge current by selecting resistor R13. Then connect the thyristor VS1 and switch the device to charging mode. Upon completion, you need to make sure that the thyristor VS1 has opened and prevented the discharge mode from being activated.

Strong heating of the batteries at the end of charging indicates that the charging current is too high; it needs to be reduced, but this will increase the charging time.

G. VORONOV, Stavropol "Radio" No. 1 2012

Nickel-cadmium batteries have become quite widespread.

There are many known ways to effectively charge nickel-cadmium (rechargeable) batteries; the described circuit is unique in that it combines almost all of their advantages. So, it produces a constant charging current, the value of which can lie in the range of 0.4-1.0 A.

The circuit can operate either from the network alternating current 220 V, or from 12 V batteries.


The rechargeable battery is protected from overcharging by automatically turning off the circuit when a predetermined battery voltage level is reached. Moreover, this level can be adjusted. Finally, the circuit is inexpensive and short-circuit proof.

If the battery is discharged, the voltage at the inverting input of the operational amplifier U1 will be lower than the voltage at the non-inverting input, set by potentiometer R1 (see figure). As a result, the output voltage of U1 will be approximately equal to the positive supply voltage, which will turn on the transistor Q1, as well as the transistor Q2, which will operate as a constant charging current generator. The level of this current can be found from the ratio (Vd-Vbe)/R6, where Vd is the voltage between its base and emitter. This current, flowing further through diode D8, charges the Ni-Cd battery. In this case, LED D7 will light up, thereby indicating the progress of the charging process and serving as an indicator of the operating mode.

As the battery charges, the voltage across it increases, which causes the voltage at the inverting input U1 to increase until it equals Vin. At this point, the output voltage of U1 drops to ground potential and transistors Q1 and Q2 are turned off, thereby preventing the battery from overcharging. The specified maximum output voltage level, Vout, can be calculated from the ratio Vout=Vin(R7+R8)/R8.

With the given values ​​of the components, the circuit produces a charging current of 400 mA, which can be changed by selecting R6 until it reaches maximum value equal to 1 A. The specified level of charging voltage should be set with the battery disconnected.

Diode D8 prevents discharge in reverse direction in the event of a power outage or 12-V power supply. For a 7.2-V Ni-Cd battery, the set charging voltage is 7.9-8.0 V. Powerful transistor Q2 should be installed on a large radiator.

The process of charging Ni-Mh batteries in aircraft modeling is slightly different from the generally accepted one. Typically, the modeler charges the batteries before heading out to the field by charging the battery overnight. But it happens that when quickly packing for flights, the batteries on board or equipment turn out to be completely or partially discharged and there is simply no time to charge them with a regular “night” charger.

The advantages of modern NiMh batteries are the ability to charge them with high current, up to 1C, without consequences for its health. The only thing you need to pay attention to when charging is the temperature and final charge voltage. You can look at the simplest charger, it is not automated and the control of the full charge is controlled by hand to increase the temperature. You can also buy a charger for all types of batteries.

To protect the battery from overcharging, voltage control can be entrusted to an automatic machine, which will turn off the battery when a certain voltage is reached and will maintain the battery in a charged state. About such automatic charger for Ni-Mh and Ni-Cd and will be discussed in this article.

Diagram of a ni-mh battery charger

Developed by me and assembled on a breadboard charger for NiMh and Ni-Cd, the circuit is simple, all elements are available.

The threshold element in the circuit is the zener diode D1; it opens when the stabilization voltage is reached, thereby opening the key on the transistors and turning on the relay, which turns off the battery. The voltage divider on R1-R2 sets the upper threshold, upon reaching which the battery is turned off; for 5 hydride cells it is 7.2v (switch s1 is closed). When the battery is connected to R5, the voltage drops to the battery voltage, and since it is less than 7.2V, D1 is closed and the relay is de-energized, while its contacts are closed and charging occurs. When 7.2V is reached, the zener diode opens, the relay is activated and disconnects the battery.

The battery voltage keeps the zener diode open and the relay on, the relay contacts remain open - this happens for some time until the battery voltage drops below 7.1V, at which time the zener diode closes and the relay again connects the battery to charge. This process is constantly repeated. The LED signals the end of charging.

Purpose of other elements charger for Ni-Mh following:

  • C1 - reduces the frequency of relay switching in the absence of a connected battery (a sign of charger operation is the relay clicking without a connected battery).
  • D2 - protects transistors from breakdown by reverse voltage arising in the relay coil.
  • R5 with a power of at least 2w - sets the charging current and is selected to obtain the desired current (12v incandescent lamps can be used instead).
  • S1 - switches modes for charging 5 can and 8 can batteries.
  • S2 is an optional element; it serves to force the charger into charge mode.
  • I don't have a relay famous brand, from the control unit of a store refrigerator.
  • D1 - can be replaced with any other 2...4v zener diode.

This is what happened to me. I installed two LEDs for beauty.

Setting up the Ni-Mh charger

Trim resistors to the middle position, connect the charger to a 12...18v power source, the relay starts to click periodically, S1 is closed, connect ni-mh battery with a voltmeter connected to it. Using resistor R1, we ensure that the LED does not glow and control the voltage on battery. When we reach 7.2V, we begin to turn R1 until the LED lights up and the relay clicks (it is advisable to perform this operation several times for more accurate positioning of the resistor). That's it, the setup for the 5-cell battery is complete.

We open S1 and do the same with the 8-can battery, only now we rotate R2 and the response threshold is 11.5...11.6v. R1 cannot be turned at this time! When charging 8 can batteries from a 12V source, the LED will not light up, there are two options: Either hang the LED on a separate pair of relay contacts, or increase the charger supply voltage to 15...18V.

Similarly, you can configure this charger to work with Ni-Cd batteries.

In the process of charging with a current of about 500 mA, heating of Ni-Mh batteries with a capacity of 1700 mA was not noticed, as happens when charging with a low current overnight, while the battery is fully charged, giving up almost all of its capacity upon further discharge.

You can set the final voltage quite accurately and with some simple modifications you can adapt two such chargers for two cans