6V Lead Acid Battery Charger using BQ24450

  • Rajkumar Sharma
  • easy
  • Tested
  • SKU: EL66206
  • Quote Now

6V Lead acid (SLA) battery charger project is based on BQ24450 IC from Texas instruments. This charger takes all the guesswork out of charging and maintaining your battery, no matter what season it is. Whether you have a Bike, Robot,  RC Car,  Truck, Boat,  RV, Emergency Light, or any other vehicle with a 6v battery, simply hook this charger maintainer up to the battery. The BQ24450 contains all the necessary circuitry to optimally control the charging of lead-acid batteries. The IC controls the charging current as well as the charging voltage to safely and efficiently charge the battery, maximizing battery capacity and life. The IC is configured as a simple constant-voltage float charge controller. The built-in precision voltage reference is especially temperature-compensated to track the characteristics of lead-acid cells, and maintains optimum charging voltage over an extended temperature range without using any external components. The low current consumption of the IC allows for accurate temperature monitoring by minimizing self-heating effects.  In addition to the voltage- and current-regulating amplifiers, the IC features comparators that monitor the charging voltage and current. These comparators feed into an internal state machine that sequences the charge cycle.

For low charging current, you can use SMD Q1 transistor on the bottom of PCB, for higher charging currents you should use a through-hole (TO247) transistor, like TIP147 on the top of PCB.

The circuit has been designed for PNP transistor (Q1) that’s why the PCB jumper is shorted to R8 by default. You can also use an NPN transistor, in this case, Omit R6, Use R2, Jumper has to be shorted the other way.


  • Supply 10V DC
  • Screw Terminals For DC Supply Input & Battery
  • Supply Current 1Amp
  • Charging Current 500mA
  • Regulate Voltage & Current during charging
  • Precision Temperature-Compensated Reference


Parts List



BQ24450 Datasheet

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I’m very interested in your circuit. Is it possible to use a solar pannel as input; if yes, what would be the optimal configuration. Then, can this device be used as an UPS (uninterruptible power supply) to plug a MCU just after the battery ?



Brad Auld

Looking at around 70 of these to eliminate batteries in apartment locks and have an external 6v sealed LA left on continuous charge, can it handled a 12v input or be trimmed to handle a 12v input (already have these)
Cheers Brad


I just saw this. I have been longing to make a 6v charger with a smart feature of regulating current supply as the battery fills. But the thing is I have a 6v 200ah which the 1amp of this charger can not serve. What can be modified to achieve a higher amp. Thanks. And also, SMD parts are not available in my country, can only get normal “Hole Mounted Parts”



I purchased one of these units and wanted to modify it to input a MAX 28VDC to charge a 12V 1.2Ah battery. The Battery part number is CP1212.

Is this possible? Can you help me?


Gergely Dr. Orsi

Dear Mike,

Can this pcb be modified to limit the charge current to 200-250mAh. I need a reliable charger for 6v 1Ah and 1.2Ah batteries. Couldn’t find any commercially available one.

Dr. Gergely Orsi


Is it possible to purchase the assembled pcb?


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