LM317 Battery Charger Circuit
According to the battery manufacturers, a battery should be charged with only 1/10 current (in ampere), of its Ah value.
For example, if a battery is of 7Ah value, then it should be charged with 0.7 Ampere current. Charging a battery using this rule, extends the battery life.
|D1||5A Diode Bridge|
|C1||1000 µF 50V|
|T1||Secondary 15V, 3AMP Transformer|
|Other||Good Heat sink|
- Charging current is controlled by T1, R1, and R4. VR1 is used to set the charging current.
- As the battery gets charged, the current flowing through the R1 increases. This result in increase in the current and voltage from the LM317.
- When the battery becomes fully charged, charger reduces the charging current to the battery, and the battery is charged in trickle charging mode.
- The input at LM317 should be around 3 volts higher than the output voltage from the LM317. As this IC requires minimum 3-volts for its operation.
- As this IC gets very hot during operation, a good heat sink should be used with this IC.
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