shared wiring: battery

Showing posts with label battery. Show all posts

Showing posts with label battery. Show all posts

Sunday, September 22, 2013

Battery Charger Display Using LT1639

The Over-the-Top type of operational amplifier is ideal for use as a current sense for battery charger applications. The design described here can be used with chargers for rechargeable batteries (Lead/acid or NiCd etc). The 5 V operating supply for the circuit is derived from the battery on charge. The circuit uses a sense resistor R8 to determine the value of current ﬂowing in or out of the battery.

An LED output shows whether the battery is charging or discharging and an analogue output displays the battery charge or discharge current. The circuit can also be altered to shown different ranges of charging current to cater for higher capacity cells. IC1a and IC1b together with T1 and T2 form two current sources, which produce a voltage across R5. The voltage across R5 is proportional to the current through resistors R8 and R1 (for IC1a) or R8-R3 (for IC1b).

The current source formed by IC1a and T1 is active when the batteries are discharging and IC1b and T2 is active when the batteries are being charged. In each case the inactive opamp will have 0V at its output and the corresponding transistor will be switched off. IC1d amplifies the voltage across R5, which is proportional to the sense current. The component values given in the diagram produce an amplification factor or 10. A sense current of 0.1 A will produce an output voltage of +1 V. The supply voltage to the circuit is +5 V so this will be the maximum value that the output can achieve. This corresponds to a maximum charge/discharge current of 0.5 A To display currents from 0 to 5.0 A, resistor R7 can be omitted to give IC1d a voltage gain of 1.

Higher currents can be displayed by using a lower value of sense resistor R8. A DVM or analogue meter can be used at Vout to give a display of the charge/discharge current. The constant current sources can only function correctly when the supply to the voltage regulator circuit (UBatt. e.g. 6V or 12V) is greater than the operating voltage of the opamps (+5 V). The supply voltage to the LT1639 can be in the range of +3 V and +44V and voltages up to 40V over the supply voltage are acceptable at the inputs to the opamp. IC1c controls the charging/discharging LED output. The inputs to this opamp are connected to the outputs of the current source opamps and its output goes high when the battery is being charged and low when it is discharging.

Monday, August 5, 2013

Mobile Cellphone Battery Charger

Charging of the mobile phone battery is a huge issue while traveling as power supply source is not usually available. In case you keep your mobile phone switched on continuously, its battery will go flat within to six hours, making the mobile phone useless. A fully charged battery becomes necessary when your distance from the nearest relay station increases. Here is a simple charger that replenishes the mobile phone battery within to hours. Fundamentally, the charger is a current-limited voltage source. Usually, mobile phone battery packs need three.6-6V DC & 180-200mA current for charging. These usually contain NiCd cells, each having one.2V rating. Current of 100mA is for charging the mobile phone battery at a slow rate. A 12V battery containing eight pen cells gives sufficient current (one.8A) to charge the battery connected across the output terminals.

Diagram of cellphone charger

The circuit also monitors the voltage level of the battery. It automatically cuts off the charging system when its output terminal voltage increases above the predetermined voltage level. Timer IC NE555 is used to charge & monitor the voltage level in the battery. Control voltage pin five of IC1 is supplied with a reference voltage of five.6V by zen-er diode ZD1. Threshold pin 6 is supplied with a voltage set by VR1 & trigger pin two is supplied with a voltage set by VR2. When the discharged mobile phone battery is connected to the circuit, the voltage given to trigger pin two of IC1 is below 1/3Vcc & hence the flip-flop in the IC is switched on to take output pin three high.

When the battery is fully charged, the output terminal voltage increases the voltage at pin two of IC1 above the trigger point threshold. This switches off the flip-flop & the output goes low to terminate the charging method. Threshold pin 6 of IC1 is referenced at 2/3Vcc set by VR1. Transistor T1 is used to enhance the charging current. Value of R3 is critical in providing the necessary current for charging. With the given value of 39-ohm the charging current is around 180 mA.

The circuit can be constructed on a tiny general-purpose PCB. For calibration of cut-off voltage level, use a variable DC power source. Connect the output terminals of the circuit to the variable power supply set at 7V. Fine-tune VR1 in the middle position & slowly fine-tune VR2 until LED1 goes off, indicating low output. LED1 ought to turn on when the voltage of the variable power supply reduces below 5V. Enclose the circuit in a tiny plastic case & use suitable connector for connecting to the cell phone battery.

Saturday, July 13, 2013

Simple Battery Low Voltage Beeper Circuit

Simple Battery Low Voltage Beeper circuit provides an audible and visual low voltage warning for 12V battery powered devices. When the battery voltage is above the set point (typically 11V), the circuit is idle. If the battery voltage should fall below the set point, the LED will light and the speaker will emit a periodic beeping sound to warn of the impending loss of power. The circuit was designed for monitoring solar systems, but it could also be useful for automotive and other 12V applications.

Specifications:

Nominal operating voltage: 12V
Idle current: 6ma
Low Voltage Warning current: 15ma

Theory:
U2 provides a 5V regulated voltage reference. U1 is wired as a comparator, it compares the fixed 5V regulated voltage to the voltage on the wiper of VR1, that is proportional to the 12V supply. When the supply drops below the set point, the output of U1 goes low, turning on Q1 and powering the beeper and the LED.

The beeper consists of U4, a tone generator, and U3, a low duty cycle pulse generator. The tone can be changed by adjusting R7, the beep rate can be changed by adjusting R5. A small amount of hysteresis is provided by R1 and the current through LED1 and the beeper, this separates the on and off points for the circuit.

Battery Low Voltage Beeper Circuit

Battery Low Voltage Beeper Circuit

Simple Battery Low Voltage Beeper circuit board was made by printing the pattern (see below) onto Press-n-peel blue circuit board transfer film with a laser printer. Etch the board, drill the holes, and assemble the parts on the board as per the board photo. Be sure to correctly orient the diode, electrolytic capacitors, ICs, and transistor. The CA3160 op-amp may be difficult to find, other low power CMOS op-amps may be substituted. A standard 741 op-amp would also work, but the idle current will be higher.

Alignment:
Connect the circuit to an adjustable DC voltage source. Set the voltage source to 11V or wherever you would like the circuit to turn on. Turn on switch S1. Adjust VR1 until the point where LED1 just comes on and the beeping starts.

Use:
Connect the circuit to the 12V source that you wish to monitor. There should be a fuse somewhere between the battery and this circuit. Turn S1 on, if the battery voltage is above the set point, nothing should happen.
As the battery voltage drops below the set point, the LED will light and a periodic beeping will come from the speaker. If the beeping becomes annoying, turn off S1. Be sure to charge the battery soon, excessive discharging will shorten the life of most rechargeable batteries.

Thursday, July 11, 2013

Car Battery Voltmeter with LED Indicator

The circuit was developed to create a voltmeter that will be used to test car batteries while showing an indication using LEDs.

Voltmeter – a device or an instrument used for measuring the electrical potential difference between two points of either alternating current or direct current electric circuit.
LM324 – has internal frequency compensated for unity gain, large DC voltage gain, wide bandwidth, wide power supply range, very low supply current drain, low input biasing current, low input offset voltage, large output voltage swing and differential input voltage range equal to the power supply voltage.

The voltage of a car battery can be measured with the use of a voltmeter as well as the charge left. A typical car battery voltage delivers around 12.6 V under no load condition and will require charging if the voltage reading is at 11.6 V. The measurement of voltage is best recommended during a high current like running the car head lights into high beam. In case the battery rapidly drops its voltage significantly under load, it would require a replacement.

This circuit will function as a comparator and will measure the car battery voltage with an interval or step of 1 V. The voltmeter will be connected across the battery terminals then starting the car. The voltage of the battery should not be measured below 10 V or else it will be considered as low in charge or low in water, since the water level of the battery should be about ¼ of an inch above the plates.

Car Battery Voltmeter with LED Indicator Schematic

Car Battery Voltmeter with LED Indicator

By applying the voltage of the battery in the inverting inputs of the amplifiers, the indicated voltage on the voltmeter is compared with the reference voltages that are produced by the Zener diode D1. The Zener diode is a special kind of diode that permits the flow of current in just one or forward direction as a normal diode, but will also allow in the reverse direction if the voltage is above or larger than a certain value of the breakdown voltage. The measured value is just enough to provide good thermic stability.

The presence of 10K trimmer RV1 is to adjust the degree of voltage that is required or desired while the visual indication will originate from the four LEDs.

R1=1K2
R2-3-4=680R
R5=15K

R6=10K
R7-8-9-10=1K
D1=5V6 /0.5W Zener

D2-3-4-5=LED
IC1=LM324
RV1=10K trimmer

The main use of the car battery voltmeter is to monitor the life and performance of batteries. It can be mounted on the dashboard that shows the battery condition to easily monitor the electrical system voltage while driving. The measurement is done by switching off the engine as well all lights and accessories and switching on the key without starting the engine. The battery is full charge if the voltmeter reads 12 V or more while a voltmeter reading of much less than 12 V signifies the battery is either discharged or failing.

Saturday, July 6, 2013

Simple 9V battery replacement circuit

This power supply circuit contains two charge-pump DC-DC converters which can delivery up to -10V for a 2,0V to 3,6V input voltage battery. For a current consumption of 7mA the output voltage it will drop to 9V, but this is enough to power a portable handheld instrument. The overall efficiency it will be up to 74% for a 2V input voltage and 60% for a 3.6V lithium polymer battery cell.

First charge-pump DC-DC converter based on MAX 619 from Maxim , C70851 smd code , delivers a regulated 5V +/- 4% output at max. 50mA. To maintain the greatest efficiency over the entire input voltage range, the MAX619s internal charge pump operates as a voltage doubler when input voltage ranges from 3.0V to 3.6V, and as a voltage tripler when it ranges from 2.0V to 2.5V.

The second charge pump converter use a TC682 circuit from Microchip and it provides an inverted doubled (-10V) output from a single positive supply (+5V regulated). An on-board 12kHz (typical) oscillator frequency provides the clock and only 3 external capacitors are required for full circuit implementation. Low output source impedance (typically 140Ω), provides output current up to 10mA.

10V DC-DC converter placement of circuit components

Components placement on printed circuit boardMore voltage convertors:

5V dc-dc converter this circuit can deliver over 1.6A at 5V and still work at 2.0V

Max761 boost converter module from 5V to 13.5V or 12V, ideal for Flash Memory Programming

Friday, July 5, 2013

24V 7Ah Lead Acid Battery Charger

This lead acid battery charger circuit is designed in response to a request from Mr.Devdas .C. His requirement was a circuit to charge two 12V/7AH lead acid batteries in series.Anyway he did not mentioned the no of cells per each 12V battery. The no of cells/battery is also an important parameter and here I designed the circuit assuming each 12V battery containing 6 cells. When two batteries are connected in series, the voltage will add up and the current capacity remains same. So two 12V/7AH batteries connected in series can be considered as a 24V/7AH battery.

24V 7Ah Lead Acid Battery Charger

24V 7Ah Lead Acid Battery Charger

The circuit given here is a current limited lead acid battery charger built around the famous variable voltage regulator IC LM 317. The charging current depends on the value of resistor R2 and here it is set to be 700mA. Resistor R3 and POT R4 determines the charging voltage. Transformer T1 steps down the mains voltage and bridge D1 does the job of rectification. C1 is the filter capacitor. Diode D1 prevents the reverse flow of current from the battery when charger is switched OFF or when mains power is not available.

Notes.

Assemble the circuit on a good quality PCB.
T1 can be a 230V primary, 35V/3A secondary step down transformer.
If 3A Bridge is not available, make one using four 1N5003 diodes.
LM317 must be fitted with a heat sink.
R2 = 0.85 ohm is not a standard value. You can obtain it by combining a 6.2 ohm and 1 ohm resistors in parallel.
F1 can be a 2A fuse.
To setup the charging voltage, power ON the charger and hook up a voltmeter across the output terminals and adjust R4 to make the voltmeter read 28V. Now the charger is ready and you can connect the batteries.
This charger is specifically designed for two 12V/7AH/6 cell lead acid batteries in series OR a 24V/7AH/12 cell lead acid battery.

Streampowers

Wednesday, May 29, 2013

Lithium battery Charger Variable current

This is a circuit of Lithium Variable battery Charger.It releases current 100mA - 2A

Note
# Fix this circuit on aPCB to get maximum advantage

Tuesday, May 14, 2013

AUTO fast battery charger for cars

This circuit is a fast and auto car charger circuit.By using this one you can charge your lead acid battery easily.After charging the battery this circuit will cut off the power to your battery. so this is very useful circuit for you.# use IC 7805 as power supply for this circuit
# LM311 control test volt battery.
# Use PCB To build your circuit.
# Be careful when you deal with 230v

Saturday, April 13, 2013

A Car Battery Monitor

A close name on the street can in reality center of consideration your thoughts on the importance of having a battery display in a car. I had been playing a nice week of touring around the united states of americaside at a leisurely tempo and taking in the beautiful surroundings on a daily basis. It wasnt until the ultimate day, with the big rush to return house, that I had to power at evening.My house is deep within the us of a and on the highway I used to be travelling the closest petrol station may be 80km away. I was traveling thru a neighborhood that is stuffed with open-cut coal mines and massive closely loaded semi-trailers continuously pound the highways, travelling at somewhat excessive velocitys. It used to be around 8pm at evening and the complete thing used to be very dark no side highway milds or home milds anyplace.

Just as I was once going up a hill, the solarshines started out to dim and the engine coughed. A massive semi-trailer loomed within the rear-vision mirror as I pushed the seize in and tried to relaxationart. My pace was falling rapidly and my lights were blacked out - I was once like a sitting duck in the direction of the highway, as the semi-trailer came swiftly bearing down on me. I simply managed to tug the auto off the street, as the semi-trailer got here screaming prior, missing me via inches! After calling for the lend a hand of the NRMA, the issue was once discovered to be a fault in the alternator, which used to be failing to charge the battery. The battery voltage had been falling underneath the heavy load of the milds and on the worst imaginable time, there was now not enough power for the lights or the motor.

After the preliminary shock wore off, I put on my thinking cap to come up with a PIC-based method to the problem. What was once in level of fact wanted used to be a show and a buzzer, to get my consideration must the voltage fall out of doors a targeted vary. So my design standards was set, a sequence of LEDs might indicate the voltage and a buzzer would also be used to warn of problems.

Main Features:

Visual indication of battery voltage
Audible warning when voltage becomes low
Screw terminals for easy connection
Simple and straightforward to construct

Circuit details:

The circuit is in line with PIC16F819 18-pin microcontroller which has an analog-to-digital (A/D) input to observe the battery voltage and outputs able to driving LEDs right away, to maintain the part count down. There are seven LEDs in all, giving a just right range of voltage indication. The topmost LED, LED1, comes on for voltages above 14V as a manner to happen when the battery is absolutely charged. LED2 point outs for voltages between 13.5V and 14V while LED3 point outs between thirteenV and 13.5V. Normally, probably the mostse LEDs shall be on. LED4 quilts 12.5V to 13V while LED5 quilts 12V to 12.5V. LED6 duvets from eleven.5V to 12V while LED7 comes on for voltages below 11.5V. These two LEDs are backed up with the help of the piezo chime which beeps for voltages between 11.5V and 12V and change intos more insistent for voltages under eleven.5V.

That might seem fairly conservative. After all, most automobiles will start and no longer using a bothers, even if the battery voltage could be a slightly under 12V, wont they? Well, no. Some brand new automotives will happily crank the motor at voltages beneath 11V however their engine management won't let the motor begin except the voltage is above 11V. So dont assume that a modern automobile will all the time begin reliably. This little battery monitor may easily prevent an extraordinarily inconvenient failure to start! So lets describe the the rest of the circuit. The incoming supply is linked by method of diode D1 which provides safety once extrast reverse polarity whereas zener diode ZD1 gives safety from spike voltages.

A usual 7805 3-terminal regulator is then used to provide a steady 5V to the microcontroller. The battery voltage is sensed by means of a voltage divider the use of 33kΩ and 100kΩ resistors. This delivers the voltage down to inside the 0-5V vary for the A/D input of the PIC16F819. Port B (RB0 to RB7) of the microcontroller is then used to force the quite loads of LEDs, with current limiting equipped by the use of the 330Ω resistor network. RB7, pin thirteen, drives a swaping transistor for the piezo buzzer.

Software:

For the software, the design follows the basic template for a PIC microcontroller. Port A and its ADC (analog-to-digital converter) operate are set up while port B functions because the output for the LEDs and buzzer. Once the set-up is full, a reading will likely be taken at port RA2, the enter for the A/D convertor. This reading is then when compared with a sequence of prices to resolve the range of the voltage. This is just like a collection of \"if\" statements in Basic language. If the voltage is found to be inside a certain vary, the related port B pin will almost definitely be fliped on. If the voltage is below 12V, the buzzer will most definitely be turned on for a brief duration, to signal a low battery situation. As the voltage falls beneath 11.5V, the frequency of the beeps will elevate, to signal elevated urgency.

Building it:

All the parts are installed on a small PC board measuring 46 x 46mm (available from Futurlec). The place to begin should be the IC socket for the PIC16F819, as this is best to mount whereas the board is naked. The next item will even be the PC terminal block. The resistors and capacitors can then follow. Make certain the electrolytics are inserted with perfect polarity.

Make sure that you don't confuse the zener (ZD1) with the diode when you in finding yourself putting in them; the diode is the larger bundle of the two.

Even extra essential, dont get the 78L05 3-terminal regulator and the 2N3906 transistor mixed up; they arrive in similar packages. The 78L05 will most certainly be labelled as such while the 2N3906 will most probably be labelled \"3906\". And you ought to definitely insert them the precise manner round. The buzzer should even be installed with the right polarity. The 330Ω current limiting resistors are all in a 10-pin in-line package. There are four green LEDs, two yellow and one crimson. They wish to be installed in line and with the precise orientation.

Testing:

Before you insert the PIC16F819 microcontroller, do a voltage examine. Connect a 12V supply and test for the presence of 5V between pins 14 & 5 OF IC1. If 5V just isn't existing, verify the polarity of regulator REG1 and the polarity of the diode D1. If these take a appear ats are OK, insert the IC and check the unit over a variety of voltage between 9V and 15V. Make positive that every one LEDs come on in sequence and the piezo buzzer beeps for voltages under 12V.

Now it is subject of putting in the unit to your automobile. It is best to install the unit in a visual position for the driving force. However, it must now not obscure every other devices. The unit will have to be linked to the autos 12V supply after the ignition switch. This will flip the unit off with the other instruments and prevent battery drain whereas the motor is simply not working.

Author :Alan Bonnard Copyright : Silicon Chip Publications Pty Ltd

Tuesday, April 9, 2013

Lead Acid Battery Charger Circuit

This circuit delivers an initial voltage of 2.5V per cell to rapidly charge a car battery. The charging current decreases as the battery charges and when the current drops to 180 mA the charging circuit reduces the output voltage to 2.35 V per cell, leaving the battery in a fully charged state. This lower voltage prevents the battery from overcharching, which will shorten its life.

The LM301A compares the voltage drop across R1 with a 18 mV reference set by R2. The comparator’s output controls the voltage regulator, and produce the lower float voltage when the battery-charging current, passing through R1, drops bellow 180 mA.
Temperature compensation helps prevent overcharging, the LM334 temperature sensor should be placed near or on the battery. Because batteries need more compensation at lower temperatures, change R5 to 30Ω for a tc of -5mV/0C per cell il this circuit will be used at temperatures below – 200C.
The charger’s input voltage must be filtered dc that is at least 3V higher than the maximum required output voltage. Choose a regulator for the maximum current needed: LM371 for 2A, LM350 for 4A, LM338 for 8A. At 250C and with no load, adjust R7 for a Vout of 7.05V, and adjust R8 for a Vout of 14.1V.

Car battery charger circuit diagram

Universal battery charger with 12V source voltage

phone battery charger with 12V source voltage

In this post I will share about using Accu source to charge batteries that can be used on any mobile brand, or can be called universal phone battery charger. Because the battery charger using a source of 12V, the charge accumulator can also be used in cars and others.

This will out charger circuit voltage of 5 volts DC, with input from at least 6 volt battery, and voltage inputs that have been tried till with 15 volts (more than it has not been tried, because the battery that tie the maximum output voltage is only 13.8 volts).

circuit universal phone battery charger

Saturday, April 6, 2013

Solar Battery Protector Prevents excessive Discharge

This circuit prevents the battery in a solar lighting system from being excessively discharged. Its for small systems with less than 100W of lighting, such as several fluorescent lights, although with a higher rated Mosfet at the output, it could switch larger loads. The circuit has two comparators based on an LM393 dual op amp. One monitors the ambient light so that lamps cannot be turned on during the day. The second monitors the battery voltage, to prevent it from being excessively discharged. IC1b monitors the ambient light by virtue of the light dependent resistor connected to its non-inverting input. When exposed to light, the resistance of the LDR is low and so the output at pin 7 is low.

Circuit diagram:

Solar battery protector prevents excessive discharge circuit schematic

Solar Battery Protector Circuit Diagram

IC1a monitors the battery voltage via a voltage divider connected to its non-inverting input. Its inverting input is connected to a reference voltage provided by ZD1. Trimpot VR1 is set so that when the battery is charged, the output at pin 1 is high and so Mosfet Q1 turns on to operate the lights. The two comparator outputs are connected together in OR gate fashion, which is permissible because they are open-collector outputs. Therefore, if either comparator output is low (ie, the internal output transistor is on) then the Mosfet (Q1) is prevented from turning on. In practice, VR1 would be set to turn off the Mosfet if the battery voltage falls below 12V. The suggested LDR is a NORP12, a weather resistant type available from Farnell Electronic Components Pty Ltd.

Author: Michael Moore - Copyright: Silicon Chip Electronics

Solar Battery Protector Circuit Diagram

This circuit prevents the battery in a solar lighting system from being excessively discharged. Its for small systems with less than 100W of lighting, such as several fluorescent lights, although with a higher rated Mosfet at the output, it could switch larger loads. The circuit has two comparators based on an LM393 dual op amp. One monitors the ambient light so that lamps cannot be turned on during the day. The second monitors the battery voltage, to prevent it from being excessively discharged. IC1b monitors the ambient light by virtue of the light dependent resistor connected to its non-inverting input. When exposed to light, the resistance of the LDR is low and so the output at pin 7 is low.

Circuit diagram:

Solar battery protector prevents excessive discharge circuit schematic

Solar Battery Protector Circuit Diagram

IC1a monitors the battery voltage via a voltage divider connected to its non-inverting input. Its inverting input is connected to a reference voltage provided by ZD1. Trimpot VR1 is set so that when the battery is charged, the output at pin 1 is high and so Mosfet Q1 turns on to operate the lights. The two comparator outputs are connected together in OR gate fashion, which is permissible because they are open-collector outputs. Therefore, if either comparator output is low (ie, the internal output transistor is on) then the Mosfet (Q1) is prevented from turning on. In practice, VR1 would be set to turn off the Mosfet if the battery voltage falls below 12V. The suggested LDR is a NORP12, a weather resistant type available from Farnell Electronic Components Pty Ltd.

Author: Michael Moore - Copyright: Silicon Chip Electronics

Wednesday, March 27, 2013

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

Saturday, March 23, 2013

Li Ion Battery Charger

The LP2951 regulator is manufactured by National Semiconductors. The choice of values is from an application note "Battery Charging", written by Chester Simpson. Diode D1 can be any diode from the 1N00x series, whichever is conveniently available. It functions as a blocking diode, to prevent a back flow of current from the battery into the LP2951 when the input voltage is disconnected. Charging current is about 100+mA, which is the internally-limited maximum current of the LP2951. For those wondering, this is compatible with just about any single-cell li-ion battery since li-ion can generally accept a charging current of up to about 1c (i.e. charging current in mA equivalent to their capacity in mAh, so a 1100mAh li-ion cell can be charged at up to 1100mA and so on).

Li-Ion Battery Charger Circuit Diagram Li-Ion Charger Circuit Diagram

Li-Ion Battery Charger Circuit Diagram Li-Ion Charger Circuit Diagram

A lower charging current just brings about a correspondingly longer charge time. IMHO 100mA is quite low, low enough that the circuit can be used for an overnight charger for many typical single-cell li-ion batteries. The resistors are deliberately kept at large orders of magnitude (tens/hundred Kohm and Mohm range) to keep the off-state current as low as possible, at about 2?A. Resistor tolerances should be kept at 1% for output voltage accuracy. The 50k pot allows for an output voltage range between 4.08V to 4.26V - thus allowing calibration as well as a choice between a charging voltage of 4.1V or 4.2V depending on the cell to be charged. The capacitors are for stability, especially C2 which prevents the output from ringing/oscillating.

Parts List:

IC1 = LP2951, voltage regulator
D1 = 1N4002, General purpose diode
R1 = 2M, 1%, metal-film
R2 = 806K, 1%, metal-film
P1 = 50K, potentiometer
C1 = 0.1uF, polyester
C2 = 2.2uF/16V, electrolytic
C3 = 330pF, ceramic

Friday, March 22, 2013

Make this Li Ion Battery Charger Circuit

It is generally advised that a Li-ion battery should be charged with utmost care and caution as these type of batteries are prone to instant damages or explosions if the specified charging measures are not employed. Here we discus a Li-ion charger circuit which has been specifically designed for charging all types Li-Ion Batteries very safely and without any considerations.

Thanks to TEXAS INSTRUMENTS for providing us with this wonderful chip, the LM3622 which is an excellent Li-Ion charger, controller device. The IC has been designed for generating a constant current at constant voltage, a basic prerequisite for all Li-Ion batteries. The IC may be configured for charging a single Li-Ion cell or a pack of many.

The circuit using the IC LM3622 can be fed with voltages right from 5 to 24V depending upon the charging needs and the connected battery. The IC does not require any precision external resistors for implementing the functions. Moreover, the IC has a negligible drain of less than 200nA of current from the battery in the absence of an input voltage.

The in built circuitry of the chip accurately regulates the charging current through the principle of temperature compensated band-gap reference. The current is regulated, however its done via an external current sensing resistor.

The band gap principle results in an efficient operating control performance of the circuit and also of the input supply voltage.

The circuit diagram illustrates a low drop out linear Li-Ion battery charger design which is capable of charging a single 3.7V Li-Ion Cell.

For enabling low voltage detection, the switches J1 and J2 may be appropriately selected.

The IC starts the charging process by first detecting the voltage of the cell and “enable status” of the low voltage detection.

The transistor Q2 immediately comes into the operating condition as soon as the connected battery hits target regulation level, determined by the internal setting of the IC.

Q2 now begins supplying a regulated voltage to the connected battery, initiating a constant voltage charging mode of the circuit.

In the above situation the battery receives a constant regulated voltage across its terminals, while the charging current is monitored depending upon the level of charge over the battery.

On reaching a full charge condition, the charge current to the battery is significantly reduced to a safe value.

For more information, you may refer to the following article.

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