DC 12V Car Battery Charger

The circuit has been designed to produce a battery charger for automobiles that are using 12V batteries only. BTY79 is a 10A Silicon controlled rectifier with an operational temperature range from 0ºC to 125ºC. C106D is a 4A sensitive gate Silicon controlled rectifier that functions as reverse blocking thyristors designed for high volume consumer applications such as light, speed control, temperature, process and remote control, and warning systems where reliability of operation is important.

Circuit Diagram:

DC 12V - Car Battery Charger Circuit Diagram

The typical car battery chargers have simple designs that produce a few amperes during its operation while charging the battery continuously. In the event that the charger is not turned OFF, overcharging will occur with due to evaporation which looses electrolyte and might cause damage to its elements. With the design of this circuit, this type of problem can be avoided by monitoring the condition of charging of the battery via the retroactive control circuit.

This is done by imposing a high current charge until the charging is complete. The LED LD2 will indicate that charging is full which will eventually deactivate the charging circuit. In creating this design, the cables that connect the transformer to the circuit should have enough cross-sectional area to prevent voltage drop when heat is produced as the current flows through. The adjustment of the circuit comes after the design, with the adjustment of TR1 to null value.

The LEDs are checked without connecting the battery initially and allowing them to turn ON. By connecting a battery, a 2A to 4A current is permitted to flow while ensuring that LD2 is turned OFF. TR1 is carefully adjusted to a few hundred milliamps until LD2 turns ON. This is done using the hydrometer technique. The correct adjustment allows LD2 to begin flickering as the battery is being charged. Connected to the battery is Q1, since it functions as a rectifier and charges the battery, which can be fired in each half cycle by R3-4 and LD2.

In case an uncharged battery is connected, a low terminal voltage is obtained. When the voltage of the battery exceeds the predetermined value, Q2 is activated by the combination of C1, TR1, R2, and D2. Q1 is deactivated with the current supply cut off as the battery terminal voltage is increased where Q2 shifts the control of Q1 gate after TR1 fixed the increased battery terminal voltage above the level. A heat sink should be mounted on the bridge rectifier GR1 and Q1 to prevent overheating. A 5A DC ammeter M1, connected in parallel, is used to measure the charge current.

The circuit’s theory of design will only be applied to batteries with rating of 12V. These batteries are mainly used in a variety of vehicles used in land, air, and water such as personal watercraft like boat, yacht, Jet Skis, and other marine applications. They are also utilized widely in automobiles and motorcycles such as quad bike, RVs, snowmobile, motor scooter, utility vehicle, and riding mower. It can also be beneficial to disabled persons by providing aid to wheelchairs and mobility scooters.

Parts:

R1= 1Kohms
R2= 1.2Kohms
R3= 470 ohms
R4= 470 ohms
R5= 10Kohms
C1= 10uF 25V
D1= 1N4001
D2= 6.8V 0.5W zener
TR1= 4.7Kohms trimmer
Q1= BTY79 or similar 6A SCR
Q2= C106D SCR
GR1= 50V 6A Bridge Rectifier
T1= 220V/17V 4A Transformer
LD1= Green LED
LD2= Red LED
M1= 0-5A DC Ampere meter
S1= 10A D/P On Off Switch
F= 5A Fuse

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High Current Battery Discharger

If you have a motley collection of 12V batteries in varying states of health, this simple circuit will allow you to easily check their capacity. Its basically a high-current discharge load which is controlled by the NiCd Discharger. This involved increasing the existing 10µF capacitor across LED1 to 100µF, to enable it to supply the brief current pulses required by the clock mechanism. The dischargers "clock connection" now controls a BC457/BD139 Darlington transistor pair (Q1 & Q2) via a 1kO resistor. These in turn activate a car headlamp relay to switch in a preselected lamp load (one of three).

With 12V selected, the prototype unit stops the discharge at 11.4V which corresponds to a cell voltage of 1.9V (this is a pretty good indication of a discharged 12V battery). The loads consist of three automotive lamps, selected to provide discharge rates to suit the battery being tested. These lamps should be fitted to sockets, so that they can be easily swapped for other lamps with different wattages, if required. That way, the discharge current can be varied simply by changing the lamp wattage. By the way, this circuit will also work with 6V batteries, provided the relay holds in. This gives an "end-point" voltage of about 5.7-5.8V.

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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 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

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Lead Acid Battery Regulator For Solar Panel Systems

The design of solar panel systems with a (lead-acid) buffer battery is normally such that the battery is charged even when there is not much sunshine. This means, however, that when there is plenty of sunshine, a regulator is needed to prevent the battery from being overcharged. Such controls usually arrange for the superfluous energy to be dissipated in a shunt resistance or simply for the solar panels to be short-circuited. It is, of course, an unsatisfactory situation when the energy derived from a very expensive system can, after all , not be used to the full. The circuit presented diverts the energy from the solar panel when the battery is fully charged to another user, for instance, a 12V ice box with Peltier elements, a pump for drawing water from a rain butt, or a 12V ventilator.

It is, of course, also possible to arrange for a second battery to be charged by the super-fluous energy. In this case, however, care must be taken to ensure that when the second battery is also fully charged , there is also a control to divert the superfluous energy. The shunt resistance needed to dissipate the superfluous energy must be capable of absorbing the total power of the panel, that is, in case of a 100W panel, its rating must be also 100 W. This means a current of some 6–8 A when the operating voltage is 12 V. When the voltage drops below the maximum charging voltage of 14.4V growing to reduced sunshine, the shunt resistance is disconnected by an n-channel power field effect transistor (FET), T1.

The disconnect point is not affected by large temperature fluctuations because of a reference voltage provided by IC1. The necessary comparator is IC2, which owing to R9 has a small hysteresis voltage of 0.5V. Capacitor C5 ensures a relatively slow switching process, although the FET is already reacting slowly owing to C4. The gradual switching prevents spurious radiation caused by steep edges of the switched voltage and also limits the starting current of a motor (of a possible ventilator). Finally, it prevents switching losses in the FET that might reach 25W, which would m a ke a heat sink unavoidable. Setting up of the circuit is fairly simple. Start by turning P1 so that its wiper is connected to R5.

When the battery reaches the voltage at which it will be switched off, that is, 13.8 – 14.4V, adjust P1 slowly until the output of comparator I C2 changes from low to high, which causes the load across T1 to be switched in. Potentiometer P1 is best a 10-turn model. When the control is switched on for the first time, it takes about 2 seconds for the electrolytic capacitors to be charged. During this time, the output of the comparator is high, so that the load across T1 is briefly switched in. In case T1 has to switch in low-resistance loads, the BUZ11 may be replaced by an IRF44, which can handle twice as much power (150 W) and has an on-resistance of only 24 mR. Because of the very high currents if the battery were short-circuited, it is advisable to insert a suitable fuse in the line to the regulator. The circuit draws a current of only 2 mA in the quiescent state and not more than 10mA when T1 is on.

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Car battery charger

Given below, is a very simple circuit that can be used for charging car batteries. In this circuit there is facility for monitoring the charging current and voltage.The circuit is based on the IC MC78T12ABT from Freescale.The IC is nothing but a 7812 in TO-3 package with 3A capacity. The transformer T1 steps the mains voltage to 15V AC and diodes D1&D2 does the job of rectification. Capacitor C1 does the filtering and C2 acts as a decoupling capacitor. The ground terminal of IC1 is lifted to 2.1V using the diodes D3 , D4 and D5 . So the output from the IC1 will be a regulated 14.1V (12+2.1).The battery is charged via diode D6.The D6 blocks reverse flow of current from battery to charging circuit when the mains power is not available. Meter M1 shows the charging current and M2 shows the charging voltage.

Notes.

* The transformer T1 can be a 230V primary; 15-0-15V, 3A secondary step down transformer.
* The meter M1 can be a 3A ammeter.
* Meter M2 can be a 20V volt meter.
* Fuse F1 can be a 1A fuse.

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USB Battery Charger Circuit Rise

In recent years, the use of USB or Universal Serial Bus as a reliable communications interface in plenty of electronic devices have increased due to its increased speed, size and flexibility. It fundamentally consists of terminals VBUS(+5V supply), GROUND, D+ and D-. As plenty of of the devices run on rechargeable battery, it is now the trend to design the charging circuit that makes use of the power supply from the USB port to charge the rechargeable battery. This feature will make the devices more convenient to the users as the devices will get their power from the bus and requires no outside plug or cables.

USB Bus Powered Functions

Theres fundamentally three classes of USB functions on power that can be derived from the port.

  High-Power Bus The high power bus powered functions derived all its power from the VBUS and cannt draw over 100mA until its been configured. One time configured, it can draw up to five unit loads(500mA) by requesting it in its descriptor. At full load, it must be able to work between the VBUS voltage of four.75V and five.25V.

  Low-Power Bus The low power bus powered functions derived all its power from the VBUS and must not draw over one unit load (100mA) according to the USB standard. It must even be able to work between the VBUS voltage of four.40V and five.25V.

  Self-Power Self power functions can draw up to 100mA from the VBUS and the rest from its outside source. This is the most simplest to design.

USB Port Powered Battery Charger

This application circuit makes use of the MCP73853/MCP73855 linear charge management controllers for cost sensitive applications. They are specially designed for USB applications and adhere to all the USB specifications governing the USB power bus. The circuit below makes use of the MCP73855 to design a USB powered Lithium Ion/Lithium Polymer battery charger by deriving the power from the USB port.

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Motorcycle Battery Monitor Circuit Diagram

A circuit for monitoring the status of the battery and generator is undoubtedly a good idea for motorcyclists, as for other motorists. However, not every biker is willing to drill the necessary holes in the cockpit for the usual LED lamps, or to screw on an analogue accessory instrument. The circuit shown here manages to do its job with a single 5-mm LED, which can indicate a total of six different conditions of the onboard electrical system. This is done using a dual LED that can be operated in pulsed or continuous mode (even in daylight). Built on a small piece of prototyping board and fitted in a mini-enclosure, the complete circuit can be tucked inside the headlamp housing or hidden underneath the tank.

 

The heart of the circuit is IC2, a dual comparator. The comparator circuit is built without using any feedback resistors, with the indication being stabilised by capacitors C4 and C5 instead of hysteresis. Small 10-µF tantalum capacitors work well here; 220-µF ‘standard’ electrolytic capacitors are only necessary with poorly regulated generators. Voltage regulator IC1 provides the reference voltage for IC2 via voltage divider R2/R3. The onboard voltage is compared with the reference voltage via voltage dividers R4 /R5 and R6/R7, which are connected to the inverting and non-inverting comparator sections, respectively.

Using separate dividers allows the threshold levels to be easily modified by adjusting the values of the lower resistors. IC2a drives the anode of the red diode of LED D4 via pull-up resistor R10. The anode of the green diode is driven by IC2b and R11. T2 pulls R11 to ground, thereby diverting the operating current of the green diode of the LED, if the voltage of the electrical system exceeds a threshold level of 15 V (provided by Zener diode D3). The paralleled gate outputs on pins 10 and 11 of IC3 perform a similar task. However, these gates have internal current limiting, so they can only divert a portion of the current from the red diode of the LED.

The amount of current diverted depends on the battery voltage. The two gates are driven by an oscillator built around IC3a, which is enabled via voltage divider R14/R15 and transistor T1 when the battery voltage is sufficiently high. Depending on the state of IC3a, the red diode of the LED blinks or pulses. The circuit is connected to the electrical system via fuse F1 and a low-pass filter formed by L1 and C1. If you cannot obtain a low-resistance choke, a 1-Ω resistor can be used instead. In this case, the values of C3, C4 and C5 should be increased some-what, in order to help stabilise the indication. D1 protects the circuit against negative voltage spikes, as well as offering protection against reverse-polarity connection. Due to its low current consumption (less than 30 mA), the circuit could be connected directly to the battery, but it is better to power it from the switched positive voltage.

Source : www.extremecircuits.net

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