LM3647 Reference Design

The LM3647 provides a single-chip charge management solution for Nickel Cadmium, Nickel Metal Hydride and Lithium-Ion cells. The device handles the entire charging process from rejuvenating deeply discharged cells to providing a number of charge termination and maintenance options. The LM3647 Demo Board allows users to create a battery charging solution with little effort.

Link : http://www.national.com/an/AN/AN-1165.pdf

7.2 Volt Field Charger

The unit is novel as it’s display graph shows you the time the battery has been charging in 2 minute intervals up to 16 minutes when finished.... read more

40 Hours of Play for those Long-Haul Flights

To prepare for the trip, we looked online for the biggest most long-lasting PSP battery pack we could find. Imagine our disappointment! We couldn't find any that went beyond about 8 hours of play time. This is no use on a 22-hour flight.

I found myself wondering why they didn't just make a PSP battery pack that could take normal batteries that you can buy at any airport. Sure, it would cost a bit to run on Duracells, but it would solve the problem of PSP power on a long flight once and for all. I seemed to recall that Duracell 'D' cells store about 12,000mAh (compared to the PSP internal battery's puny 1800mAh). And thus, the concept for the PSP Power Brick was born.

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Zinc-Carbon Battery charger

They are cheap. The electrolyte used to leak but today they are usually much better protected. If they should leak then they will corrode all the copper in your equipment. the corrosion will travel down wires and eat its way through Printed Circuit Boards (PCBs). At high temperatures (25 degrees or more) Zinc-Carbon batteries will give up to 25% more capacity but the shelf-life will deteriorate very rapidly. Around freezing point their shelf-life can be extended by as much as 300% so one tip is to store them in the refrigerator.

Unfortunately they must be thrown away when they are exhausted. You can extend their life by up to 60% by using "Dirty-DC" to recharge them but this will also reduce the shelf-life.

Ry should be about 1.5 x greater than Rx. The resistors are determined by the charging current you want. With the circuit shown and size AA cells in a pack of ten cells, the battery voltage will be 15 volts. Discharge the battery to no less than 25%. To replace 350mA/H back into the battery over 10 hours we need to charge at 35mA.

Rx = (24 - 15 - 0.7) / (3 x 0.035) = 79 ohms

Ry = (24 - 15) / (2 x 0.035) = 128

You can also cook exhausted battery cells in the oven. About 80 degrees centigrade for five to ten minutes, no more or they may explode. This technique was demonstrated on UK TV in the series "Steptoe & Son" (h�r i Sverige i "Albert och Herbert"). I do not reccomend that you should try to sell the cells again as new batteries!

Source : http://web.telia.com/~u85920178/begin/batt-00.htm

Automatic 9-Volt Nicad Charger By IC LM339 , LM317

Click to View circuit 9-V Nicad Charger

Automatic 9-Volt NiCad Battery Charger

Good care given to your NiCad batteries will ensure a long life. However, they do need to be handled and charged with special care.

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Click to View Circuit

Lead Acid Battery Charger with Float by LM350T , LM334

The circuit furnishes an initial charge voltage of 2.5 Volt-per-cell at 25°C to rapidly charge a Lead-Acid battery.
The charging current decreases as the battery charges, and when the current drops to about 180mA, the charging circuit reduces the output voltage to 2.35 Volt-per-cell, floating the battery in a fully charged state. This lower voltage prevents the battery from overcharging, which would shorten its life. The LM301A (U3) compares the voltage drop across R1 with an 18-mV reference set by R2. The comparator's output controls the voltage regulator, forcing it to produce the lower float voltage when the battey-charging current passing trhought R1 drops below 180mA. The 150mV difference between the charge and float voltages is set by the ratio of R10 and R12. The red and green Led's show this state of the circuit.

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Source :: http://www.uoguelph.ca/~antoon/gadgets/labc2.htm
By Tony van Roon

LM3909 Low-Power LED Flasher

Circuit LM3909 Low-Power LED Flasher

Low Battery Voltage Indicator by IC 8211

Circuit Low Battery Voltage Indicator by IC 8211

Car Battery Alarm

circuit Car Battery Alarm

Nicad Charger

Nicad Charger by IC CA3140E

Auto Charger battery 12V (with PCB)

circuit Auto Charger battery 12V (with PCB)
PCB Auto Charger battery 12V (with PCB)

This circuit Auto Charger battery 12V will quickly and easily charge most any lead acid battery. When the battery is fully charged, the circuit Relay switches off and lights a LED.
with IC 741 for cheker volt battery, Adj by VR1 at 14V. (Volt bat on charger)

Schematic for Battery charger

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2 Cell Lithium Ion Charger

This circuit was build to charge a couple series Lithium cells (3.6 volts each, 1 Amp Hour capacity) installed in a portable transistor radio.

The charger operates by supplying a short current pulse through a series resistor and then monitoring the battery voltage to determine if another pulse is required. The current can be adjusted by changing the series resistor or adjusting the input voltage. When the battery is low, the current pulses are spaced close together so that a somewhat constant current is present. As the batteries reach full charge, the pulses are spaced farther apart and the full charge condition is indicated by the LED blinking at a slower rate.

A TL431, band gap voltage reference (2.5 volts) is used on pin 6 of the comparator so that the comparator output will switch low, triggering the 555 timer when the voltage at pin 7 is less than 2.5 volts. The 555 output turns on the 2 transistors and the batteries charge for about 30 milliseconds. When the charge pulse ends, the battery voltage is measured and divided down by the combination 20K, 8.2K and 620 ohm resistors so that when the battery voltage reaches 8.2 volts, the input at pin 7 of the comparator will rise slightly above 2.5 volts and the circuit will stop charging.

Link : 2 Cell Lithium Ion Charger

CAR BATTERY TESTER

Checking the status of your car battery (accumulator) should be easier with this circuit which measures the internal resistance of the battery. Pulses generated by the 555 are used to drive a dummy load and the AC voltage which develops across the battery gives an indication of its internal resistance: the lower the voltage the healthier the battery. The AC voltage is read out by means of a digital meter connected at the output. Separate leads are used for the dummy load and for the metering circuit. They should be connected to their respective battery lugs but they should not touch each other. This avoids erroneous readings due to less than perfect contacts of the dummy load. The internal resistance depends on the battery temperature as well; this is the reason for the switch: hot means a battery (not ambient) temperature between 35 and 52 degrees Centigrade, normal is for a temperature between 16 and 34 degrees and cold is good for a temperature from -4 to 15. Beyond these ranges the reading is unreliable. The internal resistance depends also on the rated capacity of the battery. The 100 ohm potentiometer sets the battery capacity: it is rotated totally to positive for a 100Ah battery and totally to negative for a 32Ah battery. A dial with uniform markings from 32 to 100 was used in the prototype. This means we can measure internal resistance of batteries rated from 32 to 100Ah. As there are a number of smaller 12V batteries around, specially for alarm systems, a switch was introduced that, in the X1 position, will change the capacity range to 3.2 - 10Ah. The unit has six leads going out of the box: two for the dummy load, two for the metering section and two going to the digital meter. Operation is simple: set the range, temperature and battery rating, then connect the dummy load and the metering leads to the battery lugs and read the ac voltage: you should be safe if it reads below 10-12mV otherwise it is better to give the battery a good recharge and if it is still beyond 10-12mV then probably you need a new battery. A bright orange LED shows that the unit is connected and in operation.

From :: http://digilander.libero.it/bubblegate/eindex.html

ALKALINE CHARGER

This circuit was specifically designed to recharge alkaline cells. The unusual connection of the transistor in each charging unit will cause it to oscillate, on and off, thus transferring the charge accumulated in the capacitor to the cell. The orange LED will blink for around 5 times a second for a 1.37V cell. For a totally discharged cell the blinking is faster but it will decrease until it will come to a stop when the cell is charged. You may leave the cell in the charger as it will trickle charge and keep it at around 1.6V. To set the correct voltage you have to connect a fresh, unused cell and adjust the trimmer until oscillations set in, then go back a little until no oscillation is present and the circuit is ready to operate. You should use only the specified transistors, LED colors, zener voltage and power rating because they will set the final voltage across the cell. A simple 9V charging circuit was also included: it will charge up to around 9.3V and then keep it on a trickle charge: the green LED will be off while charging and will be fully on when the battery is close to its final voltage.

A 2.5VA transformer will easily charge up to 4 cells at the same time although 2 only are shown in the schematic. In order to minimize interference from one circuit to the other they have nothing in common except the transformer and, in order to show a balanced load to the transformer, half of the charging units will use the positive sinewave and the other half the negative sinewave. Make sure to use high beta transistors such as BC337-25 or better BC337-40. Given the dispersion of the transistor parameters it might happen that oscillations do not take place. Use a slightly higher zener voltage: 7.5V instead of 6.8 or a green led in place of the orange ones.

All types of alkaline cells can be recharged: it will take 1 day for a discharged AA cell or 9V battery and up to several days for a large D type cell. The best practice is not to discharge completely the cell or battery but rather to give a short charge every so often although admittedly this is not easy to achieve. Do not attempt to recharge a totally discharged cell or a cell showing even the slightest sign of damage.

I tried successfully to recharge NiMH cells as well. Although the charging profile for these cells is quite different from alkaline cells, the circuit seems to work fine provided you do not leave them in the charger forever, because of the possibility of overcharging especially for the smaller batteries.

The mains transformer must be suited for the voltage available in each country: usually 230Vac or 115Vac.

From :: http://digilander.libero.it/bubblegate/eindex.html

Car Battery Charger

This charger will quickly and easily charge most any lead acid battery. The charger delivers full current until the current drawn by the battery falls to 150 mA. At this time, a lower voltage is applied to finish off and keep from over charging....

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or

12V Car Battery Charger