Battery Chargers » Useful

NiMH Battery Discharger – NiCad discharger Circuit

eBatteryChargers.com — Fri, 11 Sep 2009 11:45:56 +0000

Use this NiMH battery discharger or NiCad discharger circuit when you need to discharge a battery fast and safe. This circuit is suitable for NiMH or NiCad batteries and is cheap and easy to build but the elements must be corelated with the number of battery elements.

When D2 is on, the battery is discharging whrough R4 and T1. When the battery voltage drops below the value fixed with P1, T1 wont receive base current. The LED will go off and the discharger circuit can be removed.

Battery Discharger Circuit Diagram

The battery discharger circuit can be tested with a variable power supply (with current limitator). Connect the discharger circuit at the power supply, adjust the voltage at the desired level at which T1 is blocked. Adjust P1 until D2 lights a bit.
Because the amplification is not too high, there is a zone where D2 goes off gradually and the current decrease gradually. R4 value is calculated for a discharging current of 0.5 A.

Battery Disconnect Switch

eBatteryChargers.com — Wed, 09 Sep 2009 21:34:17 +0000

This battery disconnect switch or cut-off (breaker circuit) is designed to automatically turn off any battery operated device when its user has forgotten to switch it off within a preset period of time and so it will preserve the battery’s life.

How does the the battery cut-off switch work? When the device connected to this circuit is turned on (S1), the capacitor C1 gets a voltage of +9 volts through the diode D1. The connected device is now turned on as in a normal case. C1 slowly charges via R2. After two, three minutes, the gate voltage of T3 is much reduced to a level that T3 turns off. At this time, T2 turns off the power output to the connected device.

Battery Switch Circuit Diagram

Using this battery disconnect switch circuit is simple. To build it in the device, the positive line of the power (battery) to the device must be cut and the circuit (S1 and output) connected in series to this positive line. The ground line of the circuit must be connected to the minus line.

This battery cut-off switch circuit can handle current consumptions up to 150 miliampers. Originally, it was used to control a multimeter.

Battery Monitor Circuit

eBatteryChargers.com — Sun, 30 Aug 2009 16:08:24 +0000

This battery monitor circuit is used for monitoring the battery’s condition through the three LEDs. The threshold level of the red LED is controlled by potentiometer 2, yellow by P1 and green by P3.

The setting of each pot is quite critical and must be adjusted repeatedly until the correct threshold level is reached. Finnaly, the pots must be replaced by fixed value resistance values. These resistance values can be found by measuring the actual resistance setting of each pot.

The combination of the LEDs ON condition displays the battery’s condition as shown in the table.

Battery Monitor Diagram

Battery indicator circuit

eBatteryChargers.com — Sun, 19 Apr 2009 12:28:14 +0000

This level battery indicator circuit that lets you know the battery level of a device from the number of LEDs that are glowing, it uses ten LEDs in all. So if three LEDs glow, it indicates battery capacity of 30 percent. Unlike in mobile phones where the battery-level indicator function is integrated with other functions, here only one comparator IC (LM3914) does it all.

The battery indicator circuit derives the power supply for its operation from the battery of the device itself. It uses ten LEDs wired in a 10-dot mode. Red LEDs (LED1 through LED3) indicate battery capacity of less than 40 percent. Orange LEDs (LED4 through LED6) indicate battery capacity of 40 to less than 70 percent and green LEDs (LED7 through LED10) indicate battery capacity of 70 to under 100 percent. The tenth LED glows only when the battery capacity is full, i.e., the battery is fully charged. When the battery is fully charged, relay-driver transistor T1 conducts to energise relay RL1. This stops the charging through normally-open (N/O) contacts of relay RL1.

The brightness of the LEDs can be adjusted by varying the value of preset VR2 between pins 6 and 7. For calibration, connect 15V variable, regulated power supply and initially set it at 3V. Slowly adjust VR1 until LED1 glows. Now, increase the input voltage to 15V in steps of 1.2V until the corresponding LED (LED2 through LED10) lights up.

Level battery indicator circuit diagram

Optex Campower LI5000

eBatteryChargers.com — Wed, 11 Mar 2009 21:21:17 +0000

Optex Campower LI5000 is an universal battery charger, a portable model which pulls out to reveal adjustable, electrical contacts that can be maneuvered to fit various battery sizes. Optex Campower LI-5000 will be available starting from May and will cost around $89.99 and can be used worldwide, at main power supply voltages between 100V and 240V and can gain its power via AC, 12V or USB.
Dedicated lithium-ion (Li-ion) digital camera batteries can be charged in as little as 30 minutes with the Optex CamPower Li5000 rapid charger from Gentec International. The Li5000 features an LCD display with battery fuel gauge indicator for ease of identification of charging status at any time.

12V Rechargeable battery charge monitor

eBatteryChargers.com — Thu, 05 Feb 2009 14:34:09 +0000

As per manufacturer’s data sheets, a 12V rechargeable lead-acid battery should be operated within 10.1V and 13.8V. When the battery charges higher than 13.8V it is said to be overcharged, and when it discharges below 10.1V it can be deeply discharged. A single event of overcharge or deep discharge can bring down the charge-holding capacity of a battery by 15 to 20 per cent.
It is therefore necessary for all concerned to monitor the charge level of their batteries continuously. But, in practice, many of the battery users are unable to do so because of non-availability of reasonably-priced monitoring equipment. The circuit idea presented here will fill this void by providing a circuit for monitoring the charge level of lead-acid batteries continuously. The circuit possesses two vital features:
• First, it reduces the requirement of human attention by about 85 per cent.
• Second, it is a highly accurate and sophisticated method.

Lead acid battery charge monitor circuit diagram

The circuit is powered by the battery under test, via a voltage regulator IC. The circuit takes about 100 mA for its operation.
For calibrating the upper and lower reference levels, a digital multimeter and a variable regulated power supply source are required. For calibrating the lower reference voltage, follow the steps given below:
• Set the output of power supply source to 10.1V.
• Connect the power supply source in place of the battery.
• Now the display will show some reading. At this point vary preset VR2 until the reading on the display just changes from 1 to 0.
The higher reference voltage is calibrated similarly by setting the power supply to 13.8V and varying preset VR1 until reading on the display just changes from 8 to 9.
After the calibration is completed, the circuit may be housed in a suitable enclosure. The cost of all the components, including the enclosure, would be around Rs 200.