Just like there is a ranking or grading system present for almost everything, every appliance, every product, and every process, similarly, the batteries are rated as well using a rating system.
The truth is that such a rating system is required to guide us in selecting the most appropriate battery pack depending on our specific needs and the properties the battery possess.
In the case of Lithium Polymer Battery, mainly following ratings need to be checked before deciding whether to buy or not:
Discharge (C) Rating
This is the most complicated term amongst all the ratings.
Here’s what it looks like, The discharge rate is the value that allows users to determine how much amps that the battery can continuously output without sustaining damage, it is therefore also a measure of the rate at which battery can be discharged safely that is, without harming the battery.
Many Radio control applications require high amperage, which makes it a crucial factor to know a battery’s discharge rate to ensure a vehicle’s overall performance.
What makes this complicated is that this is not a standalone number like the following two. Rather, it is a calculated figure that takes into account the capacity of the battery as well.
Capacity, in basic terms, refers to the quantum of power that a battery can hold. Say, for example, a fuel tank’s capacity is measured in terms of the amount of fuel it can hold and how long the vehicle can run before the fuel tank gets completely empty. Similarly, the capacity of a battery is the amount of power it can hold.
It is measured in milliamp hours (mAH).
Stay with me! As a consumer, all you need to know is that mAH is the amount of pressure you can put on the battery that will lead to its complete drainage in one hour. Undoubtedly, higher the number, better the battery as higher the power it can hold and therefore the run time will be higher.
Before getting into the voltage of the Lithium Polymer Battery, we should know what voltage is?
So, in simple terms, voltage determines how fast the appliance is going to run. Higher the voltage more is the speed and vice-versa. One normal LiPo battery has a nominal voltage (resting voltage of a battery pack) of 3.7V.
Now, if the appliance requires a battery of 7.4V, two LiPo cells will be required in a series. It works on a simple concept that the voltage gets added up as in the voltage of each cell installed in the series will be added up to determine the total voltage of the battery.
In our day to day lives, we often come across terms like ‘2S Battery Pack’, ‘3S Battery Pack’, ‘4S Battery Pack’ etc.
These are nothing but simple terms to understand the combination i.e., 2S refers to 2 cells in a series; 3S refers to 3 cells in a series; 4S refers to 4 cells in a series and so on. This implies that 3S Battery Pack will have a voltage of 11.1V; 4S Battery Pack will have a voltage of 14.8V and so on.
For a further explanation:
The “4S” means it has four cells in a series. Since each cell has 3.7 volts (or 4.2 volts when fully-charged), the battery has a total pack voltage of 14.8 volts or 16.8 volts. The second number, on the other hand, refers to the battery’s capacity in milliamp-hours (mAh). A 2200mAh battery at full charge can provide a current of 2200 milliamps for one hour before it becomes fully discharged.
As the name suggests, Internal Resistance is the difficulty faced by the battery in discharging its energy due to its own internal factors. Higher the internal resistance higher is the energy lost in terms of heat.
Therefore, needless to say, a high internal resistance is not good for any battery because, it shows that the energy produced by the battery doesn’t reach its required destination, rather it is lost in terms of heat. An important point to note here is that, unlike the above 3, Internal Resistance is not printed on the battery.
This is because Internal Resistance doesn’t stay constant and it changes over the life of the battery and other factors like temperature also have a bearing on it. However, that doesn’t reduce its importance. Internal Resistance is an equally important measure of the battery’s efficiency and must be taken into consideration before taking the final decision of buying the battery.