The solar battery charger circuit is nothing but a dual comparator that connects the solar panel to the battery when the voltage at the latter terminal is low and disconnected if exceeding a certain threshold. Since it is only by measuring the battery voltage, it is especially intended for lead batteries, a electrolyte liquid or gelled, that adapt the best of this way.
Description of the 12V battery charger electronic scheme :
Below is a very simple circuit that can be used to charge 12v car battery. In this circuit there is installations to control the charging current and voltage. The circuit is based on the circuit MC78T12ABT IC from Freescale. IC is actually a 7812 with a TO-3 package with a capacity of 3A.
This high performance battery charger circuit allow quickly charges gelled lead-acid batteries, and automatically turns off at full charge. First, the charge current is held at 2 A, but as battery voltage rises, the current will decreases. When current falls to 150 mA, the charger automatically switches to a lower float voltage to keep from overcharging. When you hit full charge, transistor Q1 lights the LED to indicate that status.
This mobile battery charger is designed primarily in order to give model enthusiasts the opportunity of charging their Nicad batteries from a car battery out in the open.
When the NiCd charger circuit is connected to the car battery, D2 lights only if the Nicad to be charged has been connected with correct polarity. For that purpose, the + terminal of the Nicad battery is connected to the base of T1 via R8. Because even a discharged battery provides some voltage, Ti is switched on and D2 lights.
This Lithium battery charger circuit is dedicated to charge lithium batteries. It uses 2 chips, voltage regulator LM317T and ICL7665 warns microprocessors (μPs) of overvoltage and undervoltage conditions.