Monitor De Carga Para Baterias De 12V Plomo-Acido

CIRCUIT

IDEAS

Charge Monitor for 12V Rechargeable Lead-acid Battery
battery is a vital element of any battery-backed system. In many cases the battery is more expensive than the system it isbacking up. Hence we need to adopt all practical measures to conserve battery life. 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 thecharge-holding capacity of a battery by 15 to 20 per cent. It is therefore necessary for all concerned to monitor the charge level of

RUP

ANJA

NA

SIDDHARTH SINGH AND SRINIVAS REDDY PINGLEA

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 presentedhere 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 ofhuman attention by about 85 per cent. • Second, it is a highly accurate and sophisticated method. Input from the battery under test is applied to LM3914 IC. This applied voltage is ranked anywherebetween 0 and 10, depending upon its magnitude. The lower reference voltage of 10.1V is ranked

‘0’ and the upper voltage of 13.8V is ranked as ‘10.’ (Outputs 9 and 10 are logically ORed in thiscircuit.) This calibration of reference voltages is explained later. IC 74LS147 is a decimal-to-BCD priority encoder which converts the output of LM3914 into its BCD complement. The true BCD is obtained byusing the hex inverter 74LS04. This BCD output is displayed as a decimal digit after conversion using IC5 (74LS247), which is a BCD-to-seven-segment decoder/driver. The seven-segment LED display...