Battery

A Cell is a device that stores electricity in form of chemical energy. It is the smallest unit of a battery. We combine multiple cells mostly in series and call it a Battery. Inside a cell, a reversible chemical reaction occurs. When we charge a battery inside the cell the reaction goes forward then when we discharge the battery the reaction goes backward. Although it is a reversible chemical reaction, with every cycle a small percentage becomes irreversible. This is how batteries die after a period of time.

To prevent this scenario we need to handle batteries very carefully. There are certain things that need to be maintained while using a battery.

• Temperature: Temperature is the worst enemy of a battery. It not just reduce battery life also reduces battery performence. 

• Deep Discharging: While discharging a battery we must never fully discharge a battery. If we fully discharge a battery the chemical reaction inside it becomes irriversible. Repetative deep discharging might kill the battery after a certain time.

• Over Charging: Just like Over Discharing, Overcharging also damages a battery in the same way. Deruced capacity, bad peformence might occur due to overcharging.

• Ventilation: Lead Acid batteries produces Hydrogen and Oxygen. Without proper ventilation during charging causes corotion in battery terminals.

•  Moisture: Moisture causes corotion in battery terminals.

Lead Acid Batteries:

 Depending upon the chemistry there are different types of cells. Among all of them, Lead-Acid is the most popular and widely used everywhere. 12 Volt Lead Acid batteries are made by combining 6 Nos Lead-Acid Cells together. Every Cell has multiple negative and positive plates. One disadvantage is that these have low energy density and the advantage is robustness. Depending upon the construction of the plates there are two types of Lead Acid Batteries.

• Tubuler Battery

•  Flat Plate Battery

Although the plate construction is different the chemical process remains the same. Typical construction is shown below.

Li Based Batteries:

 Now on the other hand Lithium Batteries are popular for high energy density, hence small size. Almost no maintenance. Due to these two features, these are widely used in mobile phones, laptops, drill machines, power banks, airplanes, spaceships, nowadays there are inverters that come with inbuilt Lithium batteries.

Depending upon chemical composition there are types of Lithium Based batteries:

• Li-Ion: Lithium-ion batteries are most popular for Mobile Phones. Their typical voltage is 3.7V. 
• Li-Po: Lithium Polymer batteries are mostly used in health monitoring gadgets, mobile phones.
• LiFePO4: Lithium Ferro Phosphate batteries are becoming more and more popular every day. Due to similar voltage parameters, Lead Acid batteries could be easily replaced by LIFePO4 Batteries.

Every Li-Ion cell comes with a number marking, Capacity(mAh) and Voltage printed on its body. The number marking states the dimension of the cell. Like 18650 means it has a dia of 18mm and height is 62mm.

Battery Management System:

 Battery Management System (BMS) is a device that charges and discharges Li Based batteries in a proper manner. All Li Cells of the same capacity are not identical. Hence while charging, one cell in series might get fully charged, while the others are not fully charged. The full-charged cell then stops the current to flow and due to that others, won't get charged. BMS balances all the cell so that all of them gets fully charged. BMS also provides High Temperature, Short Circuit, Deep-discharge, and Overcharge protection for each cell in a battery.

Battery Operating Voltages: