Particularly LM317 Circuit With 12v Battery Charger Circuit

The LM317 is AN adjustable three terminal transformer that is capable of supply 1.2 to 37 volts with a secure 1.5A output current. The LM317 is prepackaged terribly} normal electronic transistor package that makes it very simple to mount in your circuits.

Schematic

Overview

The LM317 series of adjustable 3-terminal positive voltage regulators is capable of supply in more than 1.5A over a 1.2V to 37V output vary. they're exceptionally simple to use and need solely 2 external resistors to line the output voltage. Further, each line and cargo regulation square measure higher than normal mounted regulators.

In addition to higher performance than mounted regulators, the LM317 series offers full overload protection out there solely in IC's. enclosed on the chip square measure current limit, thermal overload protection and safe space protection.
The LM317 makes AN particularly easy adjustable change regulator, a programmable output regulator, or by connecting a set electrical device between the adjustment pin and output, the LM317 may be used as a preciseness current regulator. provides with electronic conclusion may be achieved by clamping the adjustment terminal to ground that programs the output to one.2V wherever most masses draw very little current.

Pinout

Options

Specifications

• Guaranteed 1% output voltage tolerance (LM317A)
• Guaranteed max. 0.01%/V line regulation (LM317A)
• Guaranteed max. 0.3% load regulation (LM117)
• Guaranteed 1.5A output current
• Adjustable output down to 1.2V
• Current limit constant with temperature
• P + Product Enhancement tested
• 80 dB ripple rejection
• Output is short-circuit protected

Output Formula

Circuit
Once you have learnt enough you can now put the LM317 into use and make the following circuit:

12v Battery Charger Circuit

The circuit may be accustomed charge 12V lead acid batteries.
Overview
Pin one of the LM317 IC is that the management pin that is employed to manage the charging voltage, Pin a pair of is that the output at that the charging voltage seems, Pin three is that the input to that the regulated DC offer is given.
The charging voltage and current is controlled by the electronic transistor (Q1), electrical device (R1) and POT (VR1). once the battery is 1st connected to the charging terminals, the present through R1 will increase. This successively will increase the present and voltage from LM317. once the battery is totally charged the charger reduces the charging current and also the battery are charged within the trickle charging mode.

Circuit Diagram

Notes

• The input voltage to the circuit should be a minimum of 3V more than the expected output voltage. luminous flux unit 317 dissipates around 3V throughout its operation. Here I used 18V DC because the input.
• The charging voltage may be set by victimization the POT (VR1).
• The luminous flux unit 317 should be mounted on a sink.
• All capacitors should be rated a minimum of 25V.
• You'll be able to use crocodilian clips for connecting the battery to the charger.

 

Source: StreamPowers

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Extension for LiPo Charger

Extension for LiPo Charger Project Image

The ‘Simple LiPo Charger’ published in Elektor Electronics April 2005 is a small and handy circuit that allows you to quickly charge two or three LiPo cells. Especially in the model construction world are LiPo batteries used a lot these days, particularly model aeroplanes. It is usual to use a series connection of three cells with these models. Since working with these model aeroplanes usually happens in the field, it would be nice if the batteries could be charged from a car battery. We therefore designed a voltage converter for the LiPo charger concerned, which makes it possible to charge three cells in series. The voltage per cell increases while charging to a value of about 4.2 V, which gives a total voltage of 12.6 V. The converter, therefore, raises the 12-V voltage from the car battery to 16.5 V, from which the LiPo charger can be powered.

Extension for LiPo Charger Circuit Diagram

A step-up controller type MAX1771 in combination with an external FET carries out the voltage conversion. The IC operates at a moderately high switching frequency of up to 300 kHz, which means that quite a small coil can be used.

Because the IC uses pulse frequency modulation (PFM) it combines the advantages of pulse width modulation (high efficiency at high load) with very low internal current consumption (110µA).

The IC is configured here in the so-called non-bootstrapped mode, which means that it is powered from the input voltage (12 V). The output voltage is adjusted with voltage divider R2/R3. This can be set to any required value, provided that the output voltage is greater than the input voltage.

Extension for LiPo Charger PCB Layout

Finally, sense resistor R1 determines the maximum output current that the circuit can deliver. With the 25 mΩvalue as indicated, this is 2.5 A.

COMPONENTS LIST:

Resistors:
R1 = 25mΩ(e.g., Digikey # 2FR025-ND)
R2 = 100kΩ
R3 = 10kΩ

Capacitors:
C1,C4,C8 = 100nF
C2,C3 = 47µF 25V radial
C5,C7 = 100µF 25V radial
C6 = 100pF

Semiconductors:
D1 = 31DQ05 (e.g., Digikey #31DQ05-ND)
IC1 = MAX1771-CPA (e.g., Digikey #MAX1771EPA-ND)
T1 = IRFU3708 (e.g., Digikey #IRFU3708-ND)

Miscellaneous:
K1,K2 = 2-way PCB terminal block,lead pitch 5mm
L1 = 47µH high current suppressor
coil, (e.g, Digikey # M9889-ND)
PCB.,ref. 054012-1 from The PCBShop

Author : Unknown - Copyright : Elektor

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Motorcycle Battery Charger

Ordinary car battery chargers are simple and inexpensive devices that continuously charge the battery with a pace few amps, for the time the device is ON. If the holder does not close in time the charger, the battery will overcharge and electrowinning capacity will be lost by evaporation or likely to be destroyed elements. The charger circuit overcomes these defects. Electronically controls the battery charge and has a feedback control circuit, causing the battery to charge a maximum rate until fully charged. When fully charged, lights up a red Led (LD2).

The charger is designed to charge batteries of 12V, only. What should be paid by whom built the circuit, are the cables connecting the transformer to the circuit and then the battery should be high profile, so that heat when it passes through the current load and also not cause voltage drop in the path of current through them.

Motorcycle Battery Charger Circuit Diagram

When construction is finished turn the TR1 in place zero value, then the following settings-control.

1. Check without connecting the battery, that both LED’s light up.
2. Connect a car battery charger. Check that the LD2 is off and that a current (typically 2 until 4 A), flows to the battery.
3. Turn the TR1 and check that the LD2 can turn and charge current to cut
4. Turn the TR1 to null value and charge the battery using the standard technique hydrometer (if not available, use a battery in good condition and fully charged).

Turn carefully so that the TR1 LD2 begins to turn and charge current drops to a few hundred mA. If TR1 installed correctly then the next load will see the first LD2 will start to flicker, and charging the battery. When fully charged the battery then the LD2 will turn on fully.

To TR1 no longer needs another adjustment. The Q1 is connected in series with the circuit of the battery and can be fired from the circuit R3-4 and LD2. The battery terminal voltage is obtained from the circuit R2, C1, TR1, D2 and activates the Q2 when the voltage terminals exceeds the value we are striving to TR1.

When an uncharged battery put on charge the terminal voltage is low. under this situation the Q2 turn off and Q1, fired in each half cycle of the circuit R3-4, LD2. The Q1 functions as a simple rectifier. While charging the battery, the terminal voltage increases. If the terminal voltage rises above the level that we have set to TR1, then shifts the Q2 gate drive of Q1, it turns off, stop giving power to the battery and lights LD2, showing us that the loading is complete. The Q1 and the bridge rectifier GR1, should be placed on a good heatsink for proper cooling. The M1 is an ammeter DC 5A, so we can monitor the charging current. Optionally can be placed a voltmeter in parallel with the poles of the battery should have high input impedance, however, not affect the circuit measuring device.

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9V Automatic Battery NiCd Charger

This automatic NiCd charger for 9V NiCd batteries is using 555 timer properties and is very easy to build. Why is an automatic 9 volts NiCd battery charger? Because you can leave the battery for charging as much as you like: it will be always completely charged and ready for use when is needed. It wont be overcharged and it will not discharge.

9V Automatic Battery NiCd Charger Circuit Diagram :

With the values presented in the circuit diagram, the battery charger NiCd circuit is suitable for 6V and 9V batteries. 9 volt types with 6 and 7 cells are charging with 20mA; P1 must be adjusted so that the NiCd charger disconnects after 14 hours. Window inferior level is set at 1V below this value with P2.

5V battery type with 4 or 5 cells are charged at 55mA. Again, with P1 adjust the NiCd charger circuit so it disconnects after 14 hours. Window inferior level must be set at 0.8V below this value.

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L200 Charger Circuit

This circuit came about as the result of an  urgent need for a NiMH battery charger. No  suitable dedicated IC being immediately to  hand, the author pressed an L200 regulator and a 4.7 kΩ NTC thermistor into service.  Those components were enough to form the  basis of a charger with a cut-of f condition  based on cell temperature rise rather than  relying on the more common negative delta-V detection.

L200 Charger Circuit Diagram :

The circuit uses the L200 with the thermistor in the feedback loop. When ‘cold’ the  output volt age of the regulator is about 1.55 V per cell; when ‘warm’, at a cell temperature of about 35 °C to 40 °C, the out-put voltage is about 1.45 V per cell and the  thermistor has a resistance of about 3.3 kΩ.  This temperature sensing is enough to pre-vent the cells from being overcharged. P1  adjusts the charging voltage, and R2 limits  the charge current to 320 mA. The IC is fitted with a small 20 K/W heatsink as it dissipates around 1.2 watts in use.

The charger circuit can be connected permanently to the battery pa ck . Charging  starts when a ‘ wall wart ’ adaptor is connected to the input of the charger. The unregulated 12 V supply used by the author  delivered an open- circuit voltage of 18 V,  dropping to 14 V under load. Even though  the charge voltage is reduced when charging is complete, the cells should not be left  permanently on charge.

The author uses the circuit to charge the battery in a torch. After three years and some 150  charge cycles the cells are showing no signs of losing any capacity.

Author : Wolfgang Driehaus - Copyright : Elektor

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Battery Charger with Constant Current

T here are many ways of battery charging but constant-current charging, in particular, is a popular method for lead-acid and NiCd batteries. In this circuit, the battery  is charged with a constant current that  is generally one-tenth of the battery capacity in ampere-hours. So for a  4.5Ah battery, constant charging current would be 450 mA.

This battery charger has the following features:

1. It can charge 6V, 9V and 12V batteries. Batteries rated at other voltages can be charged by changing the values of zener diodes ZD1 and ZD2.
2. Constant current can be set as per the battery capacity by using a potmeter and multimeter in series with the battery.
3. Once the battery is fully charged, it will attain certain voltage level (e.g.13.5-14.2V in the case of a 12V battery),  give indication and the charger will switch off automatically. You need not remove the battery from the circuit.
4. If the battery is discharged be-low a limit, it will give deep-discharge indication.
5. Quiescent current is less than 5 mA and mostly due to zeners.
6. DC source voltage (V CC ) ranges from 9V to 24V.
7. The charger is short-circuit protected.

D1 is a low-forward-drop schottky  diode SB560 having peak reverse volt-age (PRV) of 60V at 5A or a 1N5822 diode having 40V PRV at 3A. Normally, the minimum DC source voltage should be ‘D1 drop+Full charged  battery voltage+V DSS + R2 drop,’ which is approximately ‘Full charged battery voltage+5V.’ For example, if we take  full-charge voltage as 14V for a 12V  battery, the source voltage should be 14+5=19V.

Circuit diagram : 

Battery Charger with Constant Current Circuit Diagram

For the sake of simplicity, this constant current battery charger circuit is divided into three sections: constant-current source, overcharge protection and deep-discharge protection sections.

The constant-current source is built around MOSFET T5, transistor  T1, diodes D1 and D2, resistors R1, R2,  R10 and R11, and potmeter VR1. Diode  D2 is a low-temperature-coefficient, highly stable reference diode LM236-5. LM336-5 can also be used with reduced operating temperature range of 0 to  +70°C. Gate-source voltage (V GS )of T5 is set by adjusting VR1 slightly above 4V. By setting V GS , charging current can be fixed depending on the battery capacity. First, decide the charging current (one-tenth of the battery’s Ah capacity) and then calculate the nearest standard value of R2 as follows: R2 = 0.7/Safe fault current R2 and T1 limit the charging current if something fails or battery terminals get short-circuited accidentally.

To set a charging current, while  a multimeter is connected in series with the battery and source supply is present, adjust potmeter VR1 slowly  until the charging current reaches its  required value. Overcharge and deep-discharge protection have been shown in dotted areas of the circuit diagram. All components in these areas are subjected to a maximum of the battery voltage and not the DC source voltage. This makes the circuit work under a wide range of source voltages and without any influence from the charging current value. Set overcharge and deep-discharge voltage of the battery using potmeters VR1 and VR2 before charging the battery.

In overcharge protection, zener diode ZD1 starts conducting after  its breakdown voltage is reached,  i.e., it conducts when the battery voltage goes beyond a prefixed high level. Adjust VR2 when the battery is fully charged (say, 13.5V in case of a 12V battery) so that V GS of T5 is set to zero and hence charging current stops flowing to the battery. LED1  glows to indicate that the battery is fully charged. When LED1 glows, the internal LED of the optocoupler also glows and the internal transistor con-ducts. As a result, gate-source voltage  (V GS ) of MOSFET T5 becomes zero and  charging stops.

Normally, zener diode ZD2 con-ducts to drive transistor T3 into conduction and thus make transistor T4  cut-off. If the battery terminal voltage  drops to, say, 11V in case of a 12V battery, adjust potmeter VR3 such that  transistor T3 is cut-off and T4 conducts. LED2 will glow to indicate that the battery voltage is low.

Values of zener diodes ZD1 and  ZD2 will be the same for 6V, 9V and 12V batteries. For other voltages, you need to suitably change the values of ZD1 and ZD2. Charging current provided by this circuit is 1 mA to 1 A, and no heat-sink is required for T5. If the maximum charging current required is  5A, put another LM236-5 in series with  diode D2, change the value of R11 to 1 kilo-ohm, replace D1 with two SB560 devices in parallel and provide a good heat-sink for MOSFET T1. TO-220 package of IRF540 can handle up to 50W.

Assemble the circuit on a general-purpose PCB and enclose in a box after setting the charging current, overcharge voltage and deep-discharge voltage. Mount potmeters VR1, VR2 and VR3 on the front panel of the box.

Author : Monoj Das - Copyright : EFY

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NiCd Battery Charger

The design of the charger is similar to that of many commercially available chargers. The charger consists of a mains adaptor, two resistors and a light emitting diode (LED). In practical use, this kind of charger is perfectly all right.

Resistor R1 serves two functions: it establishes the correct charging current and it drops sufficient voltage to light the diode. This means that the LED lights only when a charging cur-rent flows into the battery. The charging current is about 1/4 of the battery capacity, which allows a slight overcharging, and yet the charging cycle is not too long (4–5 hours).

Circuit diagram :

NiCd Battery Charger Circuit Diagram

The value of the resistors may be calculated as follows, for which the nominal e.m.f. and the capacity of the battery must be known. Adjust the output of the mains adaptor to 1.17 times the nominal battery voltage plus 3.3 V, which is the potential across R1. Note that the adaptor must be capable of supplying a current of not less than half the battery capacity.

The value of R1 in ohms is equal to 3.3 divided by 1/4 of the battery capacity. The value of the resistors for various battery voltages is given in the Table. The battery capacity is taken as 1 Ah. The rating of R1 should be 5 W. If the battery to be charged has a different capacity, the theoretical value of R1 in the table must be divided by the battery capacity. Its actual value is the nearest one in the E12 series. For instance,if a 6 V battery with a nominal capacity of 600 mAh is to be charged, the value of R1 must be 20/0.6 = 33 ½.

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Autoconnect Disconnect Battery Charger

A simple battery charger that disconnects the battery when charge voltage reaches its nominal voltage and reconnects when battery voltage falls below a predefined level, can be designed using this circuit diagram.

Circuit diagram :

Autoconnect Disconnect Battery Charger Circuit diagram

A fraction of the battery voltage is taken from the voltage divider R1-R2-R3-R4 and compare with a reference voltage with the help of IC2b. As long as the battery voltage is 0 V. The input current of AO produces a small voltage drop on R5, so IC2c pass in "0". Therefore, the relay remains disengaged.

When connecting a battery, low residual voltage provide switch of IC2c, diodes D4 and D5 are reverse biased, a voltage reference applied to the noninverting input of IC2d and relay is activated. In these conditions, the battery charge until its voltage reaches the nominal level.

Calibration is performed with a voltmeter connected to the output of IC2a, then P2 is adjusted, to obtain an indication of 3.45 V. Further, P1 rotates in the direction of maximum resistance. Replace battery with a stabilized power supply and set output voltage at 6V (6V position S1) or 12V (S1 in position 12 V), which is the voltage when charge is interrupted and adjust P1 until the relay works.

source : electroniq.net

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12v Battery Charger

Battery charger shown in this circuit diagram can be used to charge one or more batteries with a total nominal voltage of 12 V (ie ten 1.2V or six 2V NiCd batteries or lead acid ) Misuse connection is impossible, because the batteries connected with incorrect polarity, output short circuit terminal or network loss have no effect on the charger or batteries.

Circuit diagram :

Charger for 12v Battery Circuit Diagram

Power is taken from the network through a transformer secondary voltage of 18 V. The output voltage from transformer is rectified by diodes D1 - D4 and filtered by C1, resulting in a voltage of 22 V across its C1. Exhausted batteries are charged in advance with a current of about 6 mA through R2-R4-R6, D5 and D8. Once the batteries have reached a voltage around 0.3 + / - 0.5 V, base-emitter voltage of T1 is large enough to bring the transistor into conduction. Charge indicator, D6, lights and also opens T2. Through R5-R6 pass a charge current of 60 mA.

If the battery is connected with reverse polarity or shorts power transistor T2 remains blocked and the current can not exceed 6-12 mA.

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A Simple Solar Cell Power System

A solar cell power system can be built using this electronic scheme. This electronic circuit is composed of three parts: a diode, solar cell panel and a rechargeable battery. Diode prevents battery discharge through the solar panel in the absence of sunlight or low light. Although diode is usually Schottky type, the direct voltage it can produce a considerable energy loss. Circuit uses a specials diode with low direct voltage.

Circuit Diagram :

A Simple Solar Cell Power System Circuit Diagram

To adjust the circuit, replace solar panel with adjustable stabilized voltage source, with current limiter set at a level which is not dangerous to the battery. Adjust power supply output at a level higher than 0.1 V than battery voltage. Then, adjust P1 until the point where IC1's output went into logical "1". Finally, with an ammeter if the battery is discharged when the source voltage is below the current battery voltage.

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Mobile Phone Shield with Charger

This is the cell phone shield circuit which can be used as mobile charger. Give protection to your cell phone from unexpected use or theft working with this easy circuit. It is able to produce a loud chirping sound when someone tries to take away the mobile handset. The added function is that the circuit also operates as being a mobile charger.

Circuit diagram :

Mobile Phone Shield with Charger Circuit Diagram

The circuit is powered by a step-down transformer X1 with rectifier diodes D1 and D2 and filter capacitor C1. Regulator IC 7812 (IC1) together with noise filter capacitors C2 and C3 gives regulated power source. The cell phone shield circuit uses two NE555 timer ICs: One as being a very simple astable multivibrator (IC2) and then the 2nd as being a monostable multivibrator (IC3). The astable multivibrator has timing resistors R1 and R2 but no timing capacitor since it operates with stray capacitance. Its pins 6 and 2 are directly joined to a safeguarding shield built up of 10cm×10cm copper-clad board.

The inherent stray capacitance of the circuit is enough to supplied an output frequency of about 25 kHz with R1 and R2. This arrangement gives better sensitivity and allows the circuit with hand capacitance effect. Output pulses from the oscillator are immediately assigned to trigger pin 2 of the monostable multivibrator. The monostable utilizes a low-value capacitor C6, resistors R3 and preset VR1 for timing.

The output frequency of the monostable multivibrator is altered utilizing preset/trimmer VR1 such that it is slightly less than that of the astable multivibrator. This makes the circuit standby, as soon as there is no hand capacitance present. So in the standby mode, the astable’s output is going to be low. This tends to make the trigger input of monostable become low and output become high.

The warning indicator buzzer and LED1 are joined such that they come to be active only when the output of the monostable multivibrator sinks current. During the standby state, the LED1 continues to be “off” and also the buzzer is silent. As someone attempts to take the cell phone from the defending shield, his hand comes close to the shield or makes contact with the shield, which introduces hand capacitance within the circuit. Because of this, the astable’s frequency changes, which makes the trigger pin of the monostable become low and its output oscillates. This generates chirping sound from the buzzer and also makes the LED1 blink.

The circuit can even be utilized as being a mobile charger. It delivers output of 6V at 180 mA through regulator IC 7806 (IC4) and resistor R5 for charging the cell phone. Diode D3 defends the output from polarity reversal.

The circuit could be wired on a general PCB. Enclose it inside a appropriate case with provision for charger output leads. Produce the protective shield making use of 10cm×10cm copper-clad board or aluminium sheet. Hook it up towards the circuit working with a 15cm plastic wire. Leads of all capacitors ought to be short.

Fine-tune VR1 little by little working with a plastic screwdriver until eventually the buzzer stops sounding. Get the hand nearby to the shield and fine-tune VR1 right up until the buzzer sounds. With trial-and-error method, set it up for the highest level of sensitivity such that as shortly the hand comes close to the shield, the buzzer begins chirpring and also the LED blinks. As an alternative to applying the copper cladding for shield, a metallic cell phone holder can be utilized as being the shield.

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Constant Current Battery Charger

There are many ways of battery charging but constant-current charging, in particular,  is a popular method for lead-acid and Ni-Cd batteries. In this circuit, the battery  is charged with a constant current that is generally  one-tenth of the  battery capacity in ampere-hours. So for a 4.5Ah battery, constant charging current would be 450 mA.

Circuit diagram :

Constant Current Battery Charger Circuit Diagram

This battery charger has the following features:

1. It can charge 6V, 9V and 12V bat-teries. Batteries rated at other voltages can be charged by changing the values of zener diodes ZD1 and ZD2.
2. Constant current can be set as per the battery capacity by using a potmeter and multimeter in series with the battery.
3. Once the battery is fully charged,  it will attain certain voltage level (e.g. 13.5-14.2V in the case of a 12V battery),  give  indication and the charger will switch off automatically.You need not remove the battery from the circuit.
4. If  the battery is discharged  be-low a limit, it will give deep-discharge  indication.
5. Quiescent current is less than 5mA and mostly due to zeners.
6. DC source voltage (VCC) ranges from 9V to 24V.
7. The charger is short-circuit pro-tected.

D1 is a  low-forward-drop schottky diode SB560 having peak reverse voltage (PRV) of 60V at 5A or a 1N5822 diode having 40V PRV at 3A. Normally, the  minimum DC  source  volt-age  should be ‘D1 drop+Full charged  battery voltage+VDSS+ R2 drop,’ which is approximately ‘Full charged battery voltage+5V.’ For example, if we take full-charge voltage as 14V for a 12V battery, the source voltage should be 14+5=19V.

For the sake of simplicity, this constant current battery charger circuit is  divided  into  three  sections:  constant current source, overcharge protection and deep-discharge  protection  sections.

The  constant-current  source  is  built  around  MOSFET T5, transistor T1, diodes D1 and D2, resistors R1, R2,  R10 and R11, and potmeter VR1. Diode  D2 is a low-temperature-coefficient,  highly stable reference diode LM236-5.  LM336-5 can also be used with reduced  operating  temperature  range  of  0  to  +70°C. Gate-source voltage (VGS) of T5  is set by adjusting VR1 slightly above  4V.  By  setting  VGS,  charging  current  can be fixed depending on the battery capacity.  First,  decide  the  charging  current  (one-tenth  of  the  battery’s  Ah  capacity) and then calculate the nearest  standard value of R2 as follows:

R2 = 0.7/Safe fault current R2  and  T1  limit  the  charging  cur-rent if something fails or battery termi-nals get short-circuited accidentally.

To set a charging current, while a multimeter is connected  in series with the battery and source supply is present,  adjust potmeter VR1 slowly until the charging current reaches its required value.

Overcharge  and  deep-discharge  protection have been shown in dotted  areas of the circuit diagram. All  components in these areas are subjected to a maximum of the battery voltage and not the DC source voltage. This makes the circuit work under a wide range of source voltages and without any influence from the charging current value. Set overcharge  and  deep-discharge  voltage of the battery using potmeters  VR1 and VR2 before charging the battery.

In overcharge protection, zener diode ZD1 starts conducting after its breakdown voltage is reached, i.e., it conducts when the battery voltage goes beyond a prefixed high level. Adjust VR2 when the battery  is fully charged (say, 13.5V in case of a 12V  battery) so that VGS of T5  is  set to zero and hence charging current stops flowing to the battery. LED1 glows to indicate that the battery is fully charged.When LED1 glows, the internal LED of the optocoupler also glows and the internal transistor conducts. As a result, gate-source voltage  (VGS) of MOSFET T5 becomes zero and  charging stops.

Normally, zener diode ZD2 conducts to drive transistor T3 into conduction and thus make transistor T4 cut-off. If the battery terminal voltage drops to, say, 11V in case of a 12V battery, adjust potmeter VR3  such that transistor T3 is cut-off and T4 conducts.

LED2 will glow to indicate that the battery voltage is low. Values of zener diodes ZD1 and ZD2 will be the same for  6V,  9V and 12V batteries. For other voltages, you need to suitably change the values of ZD1 and ZD2. Charging  current  provided by this circuit is 1 mA to 1 A, and no heat-sink  is required for T5. If the  maximum charging current required is  5A, put another LM236-5 in series with diode D2, change the value of R11 to 1 kilo-ohm, replace D1 with two  SB560  devices in parallel and provide a good heat-sink for MOSFET T1. TO-220 pack-age of IRF540 can handle up to 50W.

Assemble the circuit on a general-purpose PCB and enclose in a box after setting the charging current, overcharge voltage and deep-discharge voltage. Mount potmeters VR1, VR2 and VR3 on the front panel of the box.

 

Author : Monoj Das - Copyright : EFY

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Solar-Powered High Efficiency Charger

This is a simple NiCd battery charger powered by solar cells. A solar cell panel or an array of solar cells can charge a battery at more than 80 % efficiency provided the available voltage exceeds the ‘fully charged’ battery voltage by the drop across one diode, which is simply inserted between the solar cell array and the battery. Adding a step-down regulator enables a solar cell array to charge battery packs with various terminal voltages at optimum rates and with efficiencies approaching those of the regulator itself. However, the IC must then operate in an unorthodox fashion (a.k.a. ‘Elektor mode’) regulating the flow of charge current in such a way that the solar array output voltage remains near the level required for peak power transfer.

Circuit  diagram :

Solar-Powered  High Efficiency Charger Circuit Diagram

Here, the MAX639 regulates its input voltage instead of its output voltage as is more customary (but less interesting). The input voltage is supplied by twelve amorphous solar cells with a minimum surface area of 100 cm2. Returning to the circuit, potential divider R2/R3 disables the internal regulating loop by holding the V-FB (voltage feedback) terminal low, while divider R1/R2+R3 enables LBI (low battery input) to sense a decrease in the solar array output voltage. The resulting deviation from the solar cells’ peak output power causes LBO (low battery output) to pull SHDN (shutdown) low and consequently disable the chip. LBI then senses a rising input voltage, LBO goes high and the pulsating control maintains maximum power transfer to the NiCd cells.

Current limiting inside the MAX639 creates a ‘ceiling’ of 200 mA for I out. Up to five NiCd cells may be connected in series to the charger output. When ‘on’ the regulator chip passes current from pin 6 to pin 5 through an internal switch representing a resistance of less than 1 ohm. Benefiting from the regulator’s low quiescent current (10 microamps typical) and high efficiency (85 %), the circuit can deliver four times more power than the single-diode configuration usually found in simple solar chargers. Coil L1 is a 100-µH suppressor choke rated for 600 mA.

Author: D. Prabakaran - Copyright: Elektor

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Auto Turn-Off Battery Charger

This charger for series-connected 4-cell AA batteries automatically disconnects from mains to stop charging when the batteries are fully charged. It can be used to charge partially discharged cells as well. The circuit is simple and can be divided into AC-to-DC converter, relay driver and charging sections. In the AC-to-DC converter section, transformer X1 steps down mains 230V AC to 9V AC at 750 mA, which is rectified by a full-wave rectifier comprising diodes D1 through D4 and filtered by capacitor C1. Regulator IC LM317 (IC1) provides the required 12V DC charging voltage.

 

Circuit diagram :

Auto Turn-Off Battery Charger Circuit Diagram

 

When you press switch S1 momentarily, the charger starts operating and the power-on LED1 glows to indicate that the charger is ‘on.’ The relay driver section uses pnp transistors T1, T2 and T3 (each BC558) to energise electromagnetic relay RL1. Relay RL1 is connected to the collector of transistor T1. Transistor T1 is driven by pnp transistor T2, which, in turn, is driven by pnp transistor T3. Resistor R4 (10-ohm, 0.5W) is connected between the emitter and base of transistor T3.
When a current of over 65 mA flows through the 12V line, it causes a voltage drop of about 650 mV across resistor R4 to drive transistor T3 and cut off transistor T2. This, in turn, turns transistor T1 ‘on’ to energise relay RL1.

 

Now even if the pushbutton is released, mains is still available to the primary of the transformer through its normally open (N/O) contacts.  In the charging section, regulator IC1 is biased to give about 7.35V. Preset VR1 is used for adjusting the bias voltage. Diode D6 connected between the output of IC1 and battery limits the output voltage to about 6.7V, which is used for charging the battery.  Pushing switch S1 latches relay RL1 and the battery cells start charging. As the voltage per cell increases beyond 1.3V, the voltage drop across resistor R4 starts decreasing. When it falls below 650 mV, transistor T3 cuts off to drive transistor T2 and, in turn, cuts off transistor T3.

 

As a result, relay RL1 de-energises to cut off the charger and red LED1 turns off.  You may determine the charging voltage depending on the NiCd cell specifications by the manufacturer. Here, we’ve set the charging voltage at 7.35V for four 1.5V cells. Nowadays, 700mAH cells are available in the market, which can be charged at 70 mA for 10 hours. The open-circuit voltage is about 1.3V. The shut-off voltage point is determined by charging the four cells fully (at 70 mA for 14 hours). After measuring the output voltage, add the diode drop (about 0.65V) and bias LM317 accordingly.

 

Author : Y.M. Anandavardhana  - Copyright : electronicsforu

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Single Lithium Cell Charger

Using the BQ24002 from Texas Instruments it  is possible to build a simple and small charger  module for single lithium-ion (Li-ion) cells. The device is available in a SSOP20 package  and so does not require heroic assembly and  soldering skills. Individual cells are becoming available from  the main catalogue suppliers, but a much  cheaper option is to rescue cells from defunct  notebook  batteries.  In  most  cases  only  a  couple of cells are faulty and the others can still look forward to a long and useful life.  A single cell is ideal for any equipment that  needs a 3.3 V power supply, and will generally give a good operating life. The charger  circuit requires a 5 V input, which can readily  be obtained from a USB port or from any 5 V  power supply.

 

Circuit diagram:

Single Lithium Cell Charger Circuit diagram

 

The  charge  process  begins  with  a  trickle  charge current. When the cell terminal volt-age is sufficiently high the charger switches  to a higher constant charge current. Charging  is terminated when the cell voltage reaches a  preset limit (the ‘final voltage’). The charger  described here is suitable for cells with a final  voltage of 4.1 V or 4.2 V, configured using  jumper JP1: pin 9 is taken to ground to select  4.1 V or to VCC to select 4.2 V.

 

It is important never to exceed the maximum  permissible cell voltage: if in doubt, consult  the manufacturer’s specifications for the  definitive value. The charge current is determined and monitored by input shunt resistor R1. A value of  0.1 Ω gives a charge current I L of 1 A: the general formula is I L = 0.1 V / R1. In this example, the input voltage should be no greater than  5.3 V to ensure that the maximum allowable  power dissipation of the IC is not exceeded.  With a charge current of 0.5 A (R1 = 0.2 Ω), the  maximum allowable input voltage is 7.6 V.

 

The circuit offers a charge time limit and cell  temperature monitoring. The charge time  limit is set using JP2. If the jumper is not fitted  charging will always stop within three hours,  even if the cell has not reached its final volt- age. If the jumper is fitted to pull pin 13 to Vcc the supply voltage) the time limit is four and  a half hours, and if pin 13 is pulled to ground  the time limit is six hours. If the final voltage  is reached early, charging will of course cease  before expiry of the time limit. The LEDs allow  the charge process to be monitored. Red LED  D1 lights during charging and flashes to indicate that a fault has been detected. When the  cell is more than 90 % charged the red LED is  extinguished and the green LED lights.

 

Pin 7 (APG/ THM) is the input to a window  comparator with a lower threshold of 0.56 V  and an upper threshold of 1.5 V. If the volt-age on this pin is over 1.5 V or below 0.56 V  the IC regards this as a fault and aborts the  charging process. Charging can only occur if  the voltage on the pin lies between the two  thresholds. The window comparator can be  used either to monitor the IC’s supply volt-age or to monitor the temperature of the  lithium cell. In the circuit shown we have  used the input in a temperature monitoring  configuration: the voltage on pin 7 is deter-mined by a voltage divider comprising R2, R3  and an NTC thermistor, which is arranged to sense the temperature of the lithium cell and  which is wired in parallel with R3 via connector K2.

 

Pin 12 (CR) carries a reference voltage  of 2.85 V; so that charging is possible under  normal conditions the thermistor and the  voltage divider of which it forms a part must  be dimensioned so that the voltage on pin 7  lies within the comparator’s voltage window  when the cell is running at a safe temperature. The values shown for R2 and R3 will  allow charging as long as the resistance of the thermistor lies between 4.8 kΩ (upper  temperature limit) and 26.6 kΩ (lower temperature limit). Using a typical 10 kΩ thermistor (such as the Vishay 2381 640 63103) this  means that charging will occur as long as the  cell temperature is between approximately  5 °C and approximately 43 °C. A 12 kΩ thermistor from the same series gives an upper  limit of 48 °C: this is the arrangement used in  Texas Instruments’ evaluation module [1].

Characteristics:

•   Designed for a single Li-ion cell
•   Suitable for all lithium chemistry cells with a final voltage of 4.1 V or 4.2 V (lithium-cobalt, lithium-manganese and lithium-polymer)
•   Configurable 4.1 V or 4.2 V final voltage
•   Input voltage from 4.5 V to 10 V (depending on charge current)
•   Charge current up to 1.2 A
•   Charge current configurable via shunt resistor
•   Linear regulator topology
•   Precharge function for deeply-discharged cells
•   Charge status indicated by two LEDs
•   Two package options: SSOP20 or QFN

Formulae are given in the datasheet [2] to  help  with  the  calculation  of  component  values in the voltage divider. Alternatively,  the TempSense Designer software [3] can be  used: it offers a graphical user interface and  a number of other features.

Link:

•  http://focus.ti.com/lit/ug/sluu113/sluu113.pdf
• http://focus.ti.com/lit/ds/slus462e/slus462e.pdf
• http://focus.ti.com/docs/prod/folders/print/bq24002.html

Author : Steffen Graf (Germany) - Copyright : Elektor

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Electric Window-Fence Charger

Here is the circuit of a simple electric window charger. With a couple of minor circuit variations, it can be used as an electric fence charger too. A standard 12V, 7Ah sealed maintenance-free (SMF) UPS battery is required for powering the entire unit. Any component layout and mounting plan can be used. However, try to keep the output terminals of transformer X1 away from the circuit board. Timer NE555 (IC1) is wired as a free-running oscillator with narrow negative pulse at the output pin 3. The pulse frequency is determined by resistors R2 and R3, preset VR1 and capacitor C3.

Circuit diagram :

Electric Window-Fence Charger Circuit Diagram

The amplitude of the output pulse can be varied to some extent by adjusting variable resistor VR1. You can vary the frequency from 100 Hz to 150 Hz. X1 is a small, iron-core, step-down transformer (230V AC primary to 12V, 1A secondary) that must be reverse connected, i.e., the secondary winding terminals of the transformer should be connected between the emitter and ground and the output taken across the primary winding.Switch S1 is used for power ‘on’/‘off’ and LED1 works as a power-‘on’ indicator. LED2 is used to indicate the pulse activity.

The output pulse from pin 3 of IC1 drives pnp transistor T1 into conduction for the duration of the time period. The collector of T1 is connected to the base of driver transistor T2 through resistor R5. When transistor T1 conducts, T2 also conducts. When T2 conducts, a high-current pulse flows through the secondary winding of transformer X1 to generate a very high-voltage pulse at the primary winding. This dangerously high voltage can be used to charge the window rails/fences. Ordinary silicon diode D1 (1N4001) protects T2 against high-voltage peaks generated by X1 inductance during the switching time. You can replace X1 with another transformer rating, and, if necessary, replace T2 with another higher-capacity transistor. The circuit can be used to charge a 1km fence with some minor modifications in the output section.

Caution:

• Take all the relevant electrical safety precautions when assembling, testing and using this high-voltage generator.

Author : T.K. Hareendran  - Copyright : EFY Mag

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Automatic Battery Charger

Normally, chargers available in the market do not have any sort of control except for a ro-tary switch that can select different tap-pings on a rheostat, to vary the charging current. This type of control is not adequate because of the irregular fluctuations in the mains supply, rendering the control ineffective.  A simple circuit intended for automatic charging of lead-acid batteries is presented here. It is flexible enough to be used for large capacity inverter batteries. Only the rating of transformer and power transistor needs to be increased.

Circuit diagram :

Automatic Battery Charger Circuit Diagram

The circuit has been basically designed for a car battery (about 40 Ah rating), which could be used for lighting two 40W tube lights. The circuit includes Schmitt trigger relay driver,float charger,and battery voltage monitor sections.  The Schmitt trigger is incorporated to avoid relay chattering. It is designed for a window of about 1V. During charging, when the battery voltage increases be-yond 13.64V, the relay cuts off and the float charging section continues to work. When battery voltage goes below 11.66V, the relay is turned on and direct (fast) charging of the battery takes place at around 3A.  In the Schmitt trigger circuit, resistors R1 and R2 are used as a simple voltage divider (divide-by-2) to provide battery voltage sample to the inverting input terminal of IC1. The non-invert-ing input terminal of IC1 is used for reference input derived from the output of IC2 (7806), using the potentiometer arrangement of resistors R3 (18 kilo-ohm) and R4 (1 kilo-ohm).

LED1 is connected across relay to indicate fast charging mode. Diodes D3 and D6 in the common leads of IC2 and IC3 respectively provide added protecion to the regulators.  The float charging section, comprising regulator 7812, transistors T3 and T4, and few other discrete components, becomes active when the battery volt-age goes above 13.64V (such that the relay RL1 is deenergised). In the energised state of the relay, the emitter and collector of transistor T4 remain shorted, and hence the float charger is ineffective and direct charging of battery takes place.

The reference terminal of regulator (IC3) is kept at 3.9V using LED2, LED3, and diode D6 in the common lead of IC3 to obtain the required regulated output (15.9V), in excess of its rated output, which is needed for proper operation of the circuit. This output voltage is fed to the base of transistor T3 (BC548), which along with transistor T4 (2N3055) forms a Darlington pair. You get 14.5V output at the emitter of transistor T4, but because of a drop in diode D7 you effectively get 13.8V at the positive terminal of the battery. When Schmitt trigger switches ‘on’ relay RL1, charging is at high current rate (boost mode). The fast charging path, starting from transformer X2, comprises diode D5, N/O contacts of relay RL1, and diode D7.

The circuit built around IC4 and IC5 is the voltage monitoring section that provides visual display of battery voltage level in bar graph like fashion. Regulator 7805 is used for generating reference voltage. Preset VR1 (20 kilo-ohm) can be used to adjust voltage levels as indicated in the circuit. Here also a pot meter arrangement using resistors R7, R8, and R9 is used as ‘divide by 3’ circuit to sample the battery voltage. When voltage is below 10V, the buzzer sounds to indicate that the safe dis-charge limit has been exceeded.

Author : Yash Deep - Copyright : EFY Mag

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NiCd Battery Charger

This NiCd battery charger can charge up to 8 NiCd cells connected in series. This number can be increased if the power supply is increased by 1.65v for each additional cell. If the BD679 is mounted on a good heatsink, the input voltage can be increased to a maximum of 25v. The circuit does not discharge the battery if the charger is disconnected from the power supply.

Circuit diagram:

NiCd Battery Charger Circuit Diagram

Usually NiCd cells must be charged at the 14 hour rate. This is a charging current of 10% of the capacity of the cell for 14 hours. This applies to a nearly flat cell. For example, a 600 mAh cell is charged at 60mA for 14 hours. If the charging current is too high it will damage the cell. The level of charging current is controlled by the 1k pot from 0mA to 600mA. The BC557 is turned on when NiCd cells are connected with the right polarity. If you cannot obtain a BD679, replace it with any NPN medium power Darlington transistor having a minimum voltage of 30v and a current capability of 2A. By lowering the value of the 1 ohm resistor to 0.5 ohm, the maximum output current can be increased to 1A.

Author : Colin Michel - Copyright : 200 Transistor Circuits

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Solar Cell Phone Charger Circuit

 

This little gadget uses a small 3 volt solar cell to charge a 6 volt NiCad battery pack which, in turn, may be used to charge many models of cell phones and other portable devices. The circuit "scavenges" energy from the solar cell by keeping it loaded near 1.5 volts (maximum energy transfer value) and trickle charges the internal battery pack with current pulses. The simple circuit isn't the most efficient possible but it manages a respectable 70% at 100 mA from the cell and 30% when the cell is providing only 25 mA which is actually pretty good without going to a lot more trouble or using more exotic components.

Note:

This circuit is intended for using a low voltage cell to charge a higher voltage battery. Don't use it to charge a battery at the same or lower voltage than the cells generate. The circuit needs a battery load to work properly. Different models of phones have different charging requirements and this charger may not work with all models.

Ref.     Description

PC1     3 volt solar cell from a sidewalk solar light
C1     22 uF, 10 volt (values not critical)
C2     100 pF, any voltage or type, typically ceramic
C3     10 uF, 16 volt or more for higher voltage battery
R1     1.5 k, any type
R2     3.9k, any type
R3     10k, any type
R4     180 ohm, any type
R5     4.7k, any type
R6     10 ohm PTC (see text).
L1     50 to 300 uH (see text)
D1     1N5818 schottky rectifier, just about any will do.
Q1     2N4403, or similar
Q2     2N4401, or similar
J1     output jack
B1     6 volt NiCad battery w/fuse

 

Here is how it works:

When the voltage on the emitter of Q1 rises a little over 1.5 volts, both transistors turn on quickly, snapping on due to the positive feedback through R5 and C2. The current increases in L1 through Q2 until the voltage across the cell drops somewhat below 1.5 volts. The circuit then switches off quickly and the voltage on the collector of Q2 jumps up, turning on D1, allowing the inductor current to flow into the battery. Once the inductor has discharged into the battery, the process starts over. The circuit can charge higher voltage batteries without any circuit changes since the voltage will jump up quite high on the collector when the transistors turn off. The circuit should not be operated without a battery attached. For a little more efficiency, increase R5 in proportion to the voltage increase on the battery. (For example, double R5 for charging a 12 volt battery.) A NiCad battery was chosen because they are particularly forgiving of overcharging, simply converting the excess current into heat.

 

The photocell was salvaged from an inexpensive solar sidewalk illuminator and it has an open-circuit voltage of about 3 volts and supplies about 100 mA in bright sunlight. The circuit can handle more current but avoid cells that supply more than 250 mA. The inductor should have a low resistance winding but a surprising number of cores will work fairly well. The core in the prototype is actually a piece of ferrite antenna rod chosen simply to fit in the extremely limited confines of the package. Another unlikely inductor that worked well was 10 turns on one of those 1" long, 1/2" diameter large ferrite beads often used for power line baluns! The value of inductance isn't critical, perhaps between 40 and 300 uH and during proper operation there will be a pulse waveform on the collector of Q2 with several 10s of microseconds period. This prototype operates at about 40 uS as shown and the inductance measures about 50 uH.

For experimenting with cores or other circuit values, replace the NiCad battery with a zener of the same voltage and replace the solar cell with a 3 volt power supply with a series resistor, about 22 ohms to simulate moderate sun. Measure the current in the zener and compare that power (zener current times zener voltage) to the power coming from the power supply (3 volts times power supply current) to see how the circuit is doing. When the power in the zener is over half the power from the supply, the inductor is good enough.

It is mandatory that a fuse be added near one of the terminals of the battery! (See the little green 2 amp fuse along the bottom edge of the battery.) Battery packs can supply dangerous current levels! Keep the lead from the fuse to the battery terminal as short as practical. I had to change this fuse; I'm glad it was there!

In addition to the fuse a 10 ohm PTC was added in series with the output to limit the available power but also to allow the unit to charge my Nokia phone which doesn't like a very low impedance battery as a charging source. (The phone simply displays "battery not charging".) I have a few thousand of those, if you need a couple (charles@wenzel.com). The PTC is actually soldered directly to the copper board and one end of the fuse connects directly to the top side.

Don't copy my assembly technique! First of all, I had to cut all the mounting posts out of the case to get the battery to fit and it is held in by glue. Notice the silver nuts soldered onto the PCB for securing the cover! Secondly, there is very little height for the circuitry so everything is pressed down flat against a piece of copper clad board using little bits of board for the connections. That's a fine technique but this prototype was just too tight for comfort. Third, I had to search a while to find an inductor that would fit! All the room was used up before I got to one of the larger parts! Having said all this, the final unit is very compact and solid but there was too much luck involved!

It works great! I simply leave it on my dash until I need it. I've charged several Nokia phones without a problem. It is actually more convenient than a cigarette lighter adapter because it can travel with the phone and it doesn't need sunlight to charge the phone. I will say that the thing charges my phone suspiciously fast and I wonder if I should increase the output resistance. Fast charging cell phone batteries shortens their life, if I understand correctly. Most phones have sophisticated internal charging circuits but I suspect the manufacturers sacrifice battery life for fast charging. It might simply be that my phone hasn't been significantly discharged since I built the charger.

Author : Charles Wenzel -Source: techlib.com

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Battery-Charging Indicator For Mains Adaptor

Although you may well be the proud owner of the very latest NiCd battery charger, you may still come across the odd 'incompatible' battery, for example, one having a rare voltage or requiring a much higher charging current than can be supplied by your off-the-shelf charger. In these cases, many of you will resort to an adjustable mains adaptor (say, a 500-mA type) because that is probably the cheapest way of providing the direct voltage required to charge the battery. Not fast and not very efficient, this 'rustic' charging system works, although subject to the following restrictions:
Circuit diagram:

Battery-Charging Indicator Circuit Diagram

1. You should have some idea of the charging current. In case you use an adaptor which is adjustable but of the unregulated, low output current type, you can adjust the current by adjusting the output voltage.
2. You have to know if the current actually flows through the battery. A current-detecting indicator is therefore much to be preferred over a voltage indicator.
3. To prevent you from forgetting all about the charging cycle, the indicator should be visible from wherever you pass by frequently. Using the circuit shown here, the LED lights when the baseemitter potential of the transistor exceeds about 0.2 V. Using a resistor of 1 ? as suggested this happens at a current of about 200 mA, or about 40 mA if R1 is changed to 4.7?. The voltage drop caused by this indicator can never exceed the base-emitter voltage (UBE) of the transistor, or about 0.7V. Even if the current through R1 continues to increase beyond the level at which UBE = 0.7 V, the base of the transistor will 'absorb' the excess current. The TO-220 style BU406 transistor suggested here is capable of accepting base currents up to 4A. Using this charging indicator you have overcome the restrictions 2 and 3 mentioned above.

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