Saturday, March 16, 2013

Make this 48V Automatic Battery Charger Circuit

The following article explains a very simple yet effective 48v automatic battery charger circuit, utilizing very ordinary components. The circuit is highly accurate with  its over charge cut off features.

Circuit Description

As shown in the figure, the main element in the circuit is the opamp IC 741, which has been arranged as a comparator.

Pin#3 which is the inverting input of the IC is referenced with a fixed voltage of 4.7V through the respective  zener/resistor network.

The other input is applied with the sensing voltage which is actually the voltage merged from the supply and the from the  battery, in other words the charging voltage which is applied to the battery for charging.

The resistor network at pin#2 along with the preset forms a voltage divider network which is initially adjusted such that the voltage at this pin stays below the voltage level at pin3, which is the reference voltage set at 4.7v by the zener diode.

The preset is set in such a way that the voltage at pin#2 rises above the 4.7 mark as soon as the battery voltage rises above 50V or the fill charge threshold level of the battery.

The moment this happens, the output of the op amp goes low switching OFF the mosfet, and cutting off the voltage to the battery.

Initially as ling as the battery voltage and the over all voltage from the 48V supply remains below the full charge threshold level of the battery, the output of the opamp stays high and the mosfet us kept switched ON. This allows the voltage to the battery for charging, until the above explained threshold is reached which automatically inhibits the battery from further charging.
The mosfet can be selected as per the AH rating of the battery.

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