• Skip to main content
  • Skip to primary sidebar

Homemade Circuit Projects

Get free circuit help 24/7

Circuits for Beginners | Basic Circuits | LED Driver | Hobby Circuits | Transistor Circuits

New-Projects | Privacy Policy | About us | Contact | Disclaimer | Copyright | Videos

You are here: Home / Battery Chargers / Charging a Deep Discharged Battery

Charging a Deep Discharged Battery

Last Updated on June 12, 2021 by Swagatam 6 Comments

ask questions through comments

In the following post we discuss an advanced battery charger circuit that can be used for charging a deep discharged lead acid battery in a stage wise manner.

Figure 1 below demonstrates possibly the perfect charge current characteristic that can be achieved for a standard 12 V lead acid battery in its fully or deeply discharged condition.

At the initial charging phase (A-B), a controlled low charging current is used, until the battery voltage attains around a 10 V level. This low current controlled charging is necessary to make sure that the devices of the circuit does not get too much hot initially.

During the next charging stage (C-D), the charging to the battery is done with a 5 hour charging current rate. This current level can be estimated by dividing the printed Ah spec of the battery by 5. This charging phase can be assumed to be complete when the battery voltage reaches 14.4 V. At this point, the final charging phase is executed (E-F).

In this phase battery is charged using a significantly scaled-down top-up current, which slowly and automatically drops down to zero when the battery terminal voltage touches the 16.5 V mark.

How the Circuit Works

The circuit concept explained here for charging a deeply discharged lead acid battery is designed to deliver a charge cycle which is exactly as per the steps discussed above.

If you have a 12V battery that is fully or deeply discharged at below 10V, that will allow a very small current to pass by means of D3. Due to this the transistor T1 will remain switched off.

Because of this IC1 output will stay low, which will enable the transistors T2 and T3 to get its base current from the low op amp output.

With T2, T3 switched ON the charging current to the battery, can be entirely set as required through the preset P1.

While the battery charges, as soon as its voltage reaches a value of 14 V, causes the diode D3 to get forward biased, which in turn causes transistor T1 to switch ON.

Even at this point the IC1 output continues to be low, which means now the charging current is decided by the presets P1 and P2 both.

In this situation, the setting of P3 causes the voltage at the non-inverting pin of the op amp to increase beyond the zener voltage of D1, then because of the positive feedback arriving from the resistor R4, the IC1 op amp output voltage now switches high, up to a level as determined by the D1 zener voltage, along with the forward voltage drop of diode D2.

With the op amp output turning high, switches OFF the transistor T1, which yet again allows the charge current to be determined by the adjustment of preset P1.

However, contrary to the charging phase A-B, the IC1 output turning high signifies that current would flow by means of the preset P1, and as a result the charging current to the deeply discharged battery would be decreased proportionately.

Because the diode D2 is forward biased, the resistors R2 and R3 will help to progressively minimize the charging current further and further as the battery slowly charges and its voltage gradually increases.

How to Calibrate

In order to adjust the circuit, you must first begin setting up preset P3 so that the IC1 output goes high in a situation when the output of the circuit or battery voltage attains 14.4 V.

Next using the preset P1 the 'boost' charge current must be adjusted to the 20-hour level (which is determined by dividing the battery in Ah by 20), for the battery voltage levels between 14.5 and 15 V.

Lastly, using a battery voltage between 11 and 14 V, start setting up the preset P2 until a nominal 5 hour (battery Ah divided by 5) charging current is fixed.

The starting charging current (phase A-B) can be adjusted depending upon the value of the top-up current, and also according to the specifications of the transistors, wherein the transistors current handling specs should be approximately 50 to 100% greater than the top-up current.

Parts List for the Deep Discharge Battery Charger

PCB Design

get free help for circuit diagrams

You'll also like:

  • 1.  Ni-Cd Low Battery Monitor Circuit using Lambda Diode
  • 2.  PWM Solar Battery Charger Circuit
  • 3.  Convert SMPS into a Solar Charger
  • 4.  12V LED Backpack Power Supply Circuit
  • 5.  3 Step Automatic Battery Charger/Controller Circuit
  • 6.  Solar Water Heater Circuit with Battery Charger

About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

Subscribe for the Latest Posts


 

Reader Interactions

Comments

    Have Questions? Please post your comments below for quick replies! Comments should be related to the above artcile Cancel reply

    Your email address will not be published. Required fields are marked *

  1. stanley says

    October 5, 2021 at 9:08 am

    hola me gustaria saber si este circuito se podria adaptar para 48 voltios y que tendria que cambiar del mismo. gracias

    Reply
    • Swagatam says

      October 5, 2021 at 1:20 pm

      Hello, it seems difficult to convert this charger into a 48V charger since there are many things that would need to be changed….

      Reply
  2. Laurie Charles says

    June 24, 2021 at 3:18 am

    I have been told that to charge multiple Deep cycle batteries set up in parallel that I would need a 60 amp 7 stage charging unit….. this setup is for use in a home…. What is you thoughts on this charger and do you have a circuit design for one. professional ones are just to expensive and I prefer making my own stuff anyway.

    Reply
    • Swagatam says

      June 24, 2021 at 8:41 am

      There’s a simple way to do it.
      Connect all the positives of battery together and connect it to the positive of a charging supply.

      After this connect the following module between the charger negative and the battery negative. You will have to connect each of these modules individually the between the negative line and the negative of the battery:
      https://www.homemade-circuits.com/wp-content/uploads/2020/03/battery-charger-circuit.png

      Reply
      • Doug says

        February 16, 2022 at 1:32 am

        would this circuit work with a 75 amp power supply?
        It wouldn’t be possible to keep multiple batteries in parallel while charging, would it?
        Is this essentially a rescue circuit for deeply discharged LAB?
        Thanks
        Doug

        Reply
        • Swagatam says

          February 16, 2022 at 11:11 am

          This circuit can be modified for monitoring any battery with any power rating, by replacing T3 with a p channel mosfet, rated appropriately. You can charge multiple batteries in parallel, by having separate diodes in series with their positive lines. This design may work to revive dead batteries but there’s no guarantee about the success rate for this.

          Reply

Primary Sidebar



Categories

  • 3-Phase Power (15)
  • 324 IC Circuits (19)
  • 4017 IC Circuits (52)
  • 4060 IC Circuits (25)
  • 555 IC Circuits (98)
  • 741 IC Circuits (19)
  • Amplifiers (59)
  • Arduino Engineering Projects (83)
  • Audio Projects (94)
  • Battery Chargers (83)
  • Car and Motorcycle (94)
  • Datasheets (46)
  • Decorative Lighting (Diwali, Christmas) (32)
  • DIY LED Projects (89)
  • Electronic Components (97)
  • Electronic Devices and Circuit Theory (35)
  • Electronics Tutorial (109)
  • Fish Aquarium (5)
  • Free Energy (34)
  • Fun Projects (12)
  • GSM Projects (9)
  • Health Related (19)
  • Heater Controllers (28)
  • Home Electrical Circuits (100)
  • How to Articles (20)
  • Incubator Related (6)
  • Industrial Electronics (28)
  • Infrared (IR) (40)
  • Inverter Circuits (98)
  • Laser Projects (12)
  • LM317/LM338 (21)
  • LM3915 IC (25)
  • Meters and Testers (64)
  • Mini Projects (156)
  • Motor Controller (66)
  • MPPT (7)
  • Oscillator Circuits (24)
  • PIR (Passive Infrared) (8)
  • Power Electronics (33)
  • Power Supply Circuits (74)
  • Radio Circuits (9)
  • Remote Control (47)
  • Security and Alarm (61)
  • Sensors and Detectors (118)
  • SG3525 IC (5)
  • Simple Circuits (74)
  • SMPS (29)
  • Solar Controllers (60)
  • Timer and Delay Relay (53)
  • TL494 IC (5)
  • Transformerless Power Supply (8)
  • Transmitter Circuits (40)
  • Ultrasonic Projects (14)
  • Water Level Controller (45)


Circuit Calculators

  • AWG to Millimeter Converter
  • Battery Back up Time Calculator
  • Capacitance Reactance Calculator
  • IC 555 Astable Calculator
  • IC 555 Monostable Calculator
  • Inductance Calculator
  • LC Resonance Calculator
  • LM317, LM338, LM396 Calculator
  • Ohm’s Law Calculator
  • Phase Angle Phase Shift Calculator
  • Power Factor (PF) Calculator
  • Reactance Calculator
  • Small Signal Transistor(BJT) and Diode Quick Datasheet
  • Transistor Astable Calculator
  • Transistor base Resistor Calculator
  • Voltage Divider Calculator
  • Wire Current Calculator
  • Zener Diode Calculator


You can also Chat with me here:

Facebook
Twitter
YouTube
Instagram
My Facebook-Page
Quora



© 2022 · Swagatam Innovations

We use cookies on our website to give you the best experience.
Cookie settingsAccept All
Privacy & Cookies Policy

Privacy Overview

This website uses cookies to improve your experience while you navigate through the website. Please visit the Privacy Policy Page for more info.
Necessary
Always Enabled
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
Non-necessary
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.
SAVE & ACCEPT