12 Volt Gel cell Battery Charger Circuit

Simple 12 volt gel cell battery charger circuit constructed by using few easily available components. This circuit can charge gel cell battery with reverse current and overcharging protection. We know a Gel cell battery is a VRLA (valve regulated lead-acid) battery with a gelified electrolyte, and this type of batteries are maintenance free batteries.




This 12 Volt Gel cell Battery Charger Circuit utilize 15 Volt to 18 Volt DC input supply and provides Regulated 12 Volt DC supply to the charging Battery. This circuit designed with adjustable charging current and indicator LED.

Circuit Diagram

Components Required

  1. Voltage Regulator IC LM317
  2. Transistor 2N2222A (NPN)
  3. Resistors 1KΩ, 470Ω,2.2KΩ each one
  4. Resistor 1Ω/2W
  5. Variable Resistor 10KΩ
  6. Capacitors 0.1µ = 2
  7. LED green

Construction & Working

This charger circuit designed to meet the requirements of Gel cell batteries and this circuit capable of charging 12 Volt battery. Main part of this circuit is Positive Adjustable voltage Regulator IC LM317 and use heat sink for this IC. Place Transistor 2N2222A between Adj pin of Regulator and ground supply Base terminal and emitter terminals are separated by the Resistor R2 and this transistor helps to maintain constant current at the output. Resistors R3, RV1 and R4 are connected serially between output bias and Variable Resistor terminal is connected with Adj pin of Regulator. Here Red LED indicates the charging current.

Gel Cell Battery

2N2222A Transistor Pin Details

2N2222A is a Three terminal NPN transistor comes in TO-92 package and first terminal is Emitter, Second terminal is Base and Third terminal is Collector. Place this transistor in circuit with proper pin configurations.

Input Supply for this circuit can be 15 Volt DC to 18 Volt DC supply and use proper Step down transformer and Bridge rectifier for input supply, at the end this circuit will provide 12V DC with adjustable current. Place the Gel Cell battery at the end with proper polarity.




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