4V Lead Acid Battery Charger

Introduction: 4V Lead Acid Battery Charger

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// Update 02/2018. - You can use any Li-ion charger which is used to charge phone's 3.7v Battery as they both are charged with a 4.2V DC. but if you still want to make one of your own... just go through this instructable.

MY First Instructables Friends ,

So this is for those who are new to Lead Acid batteries and about charging them , A cute Little 4V battery charger

SO What we need to charge a 4V Lead acid battery, all we need is A 5V regulated supply, and let's make it ......


1. 5V Voltage Regulator ..... ----- I.e . Ls7805

2.Header Pins Or anything you want to use to connect the battery to circuit

3. 1N4001 rectifier Diode

4.An ECB, Or breadboard or anything like that........

Step 1: The Circuit

First you need a DC power source Which Is Greater than 7Volts for the battery charger to work correctly, you can attach a laptop charger with a dc jack , or you can also use a set top box Adapter. and at the output of voltage Regulator connect the battery

Circuit is In the pictures


My Other Projects

1 Wireless Electricity Module

2 .Function Generator

3. JTAG ICE with Arduino IDE

4. Getting Started With JTAGICE Clone


Step 2: FINISHED ............

don't mind about the capacitor, it in not used in circuit............



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    12 Discussions


    I have a confusion, please tell me max voltage of 4V Sealed Lead acid battery and also specify minimum voltage of battery.
    thanks in advance.

    1 reply

    these batteries works on the same voltages as other lithium ion phone batteries..... and can be charged with a compatible charger ... so min voltage is around 3.6 - 3.7V and max voltage is 4.2 to 4.3V. hence using a diode after 7805 will further step down voltage to 4.3V.

    How much time this circuit would take to fully charge battery

    actually the best solution for these batteries are those li-po or ni-cd battery chargers

    I think , charging voltage per cell should be 2.3V to 2.45V and a charging current of c/10. http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

    so for a 4V 500mAh battery it should be 4.6 to 4.9 @ 50 mA . I have Sunca 4v 1000mAh and i am looking forward to make a charger.

    Cnt we just use a 5v adapter and a diode to charge it ???

    1 reply

    and yes , yogeshwara, you can ,but with a ressistor. in series...

    and let me remind you.....more the current will be (greater than 41.6%) more is the possibility of damaging the battery.... for limiting the current you can use a resistor .

    actually the indicator is a problem for mee to (Actually I am working on it..)..... but you can check the status of battery by measuring the voltage by voltmeter the voltage of a fully charged battery is 4.2V , and never use a power supply of more than 41.6% current of that of the capacity of battery else it will cause the sulphuric acid inside to boil.... that's the reason why I am working on a newer version..... it would be coming soon.... by the end of may....

    Cnt we just use a 5v adapter and a diode to charge it ???

    How to know when it is fully charged