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