How to make dead Lead Acid Battery work again

In this post, I am going to share my experience of making a dead lead-acid battery work again. Maybe trick in this post will help you to recover your lead acid battery.
First, let me share my experience. I had a 12 V lead-acid battery whose voltage went down below 9 volts and when I try to charge this battery its voltage suddenly goes above 14 volts. If you're facing this problem than the solution in this post might help you. I made the same battery work 2 times using the method mentioned in this post and the battery is still in working condition when I am writing this post.
So what should we do in such a situation? Logically thinking current going inside the battery is too much and this too much current makes the voltage go high suddenly. So how to reduce this current? How much current should we provide for charging the battery?
To solve this problem without using a complicated electronic circuit. We can simply place a suitable load parallel to the battery. This load should maintain a voltage between 12-13 V across the battery. So what will happen from this? The battery will take the current it needed and the load will take extra current. This load can be a dc motor or any resistive load.
As the battery start recovering it will take more and more current and current through load will automatically decrease. It may take from half an hour to a few hours for the battery to recover. Once the battery start taking more current you can remove the load and let the battery charge.

Hanging problem and back Emf

In this post, I am gonna share a hanging problem of a microcontroller that is related to back emf. I faced this problem when I was using the Arduino microcontroller in a high-speed switching circuit. The microcontroller stops working a few seconds after switching on the circuit. No damage to the microcontroller in my case, after reset microcontroller works in the same way.

 When we use devices like relay or motors with microcontrollers and operate them through a driver IC. During switching on and off there is back emf generated. This back emf can cause damage to the microcontroller.

 

When the switch opens at t=0 the current 'I' sees high resistance. This high resistance path can be any insulator or air itself.

What is back emf? Inductor has a property that current cannot change instantaneously through them. Due to this property when we remove supply from inductor the current flowing through it needs a path. When it finds no low resistance path large voltage spike is produced. Why? It takes the high resistance path which can be insulator or air. This high voltage spike can damage our equipment.

How to solve this problem? To solve the problem we should provide a low resistance path to this current. When this current goes through a low resistance path, the voltage developed becomes negligible. Usually, in circuits high-speed diode is used for this purpose. See the figure below how current passes through the diode when the switch opens at t=0.