Introduction
Batteries are the most important part of the design when it comes to hobby-bots. Care is always required to choose the right batteries for the job. But many a times we just choose a random battery because our minds are more preset on the working principle of the robot. Little do we realize that choosing the right battery can actually solve a lot of problems. Through the numerous competitions we've seen in the last few years, many bots fail to start, fail to complete the course mainly due to what the competitors loosely put as 'power problems' . Lets look closer into what these problems are and how they can be prevented.
Types of batteries
There are many many types of batteries out there and we shall look into a few of them and in general how to choose the ratings on the batteries. Of the few we shall consider are the normal AA,AAA, D and button batteries. Also we shall consider the rechargeable batteries also. The main features to consider about a battery are the voltage and the current rating.
AA batteries
AA batteries are the most commonly available batteries in any shop.These have generally low voltage and low current ratings. A typical Eveready or Phillips battery is of the rating of 1.5V and 1100mAh. This can be found written on the battery itself. Two AA batteries usually power up pen torch,old radio sets, TV remote controls..etc
AAA batteries
AAA batteries are also quite common these days. They usually have a lower rating than that of AA batteries. With the advent of new technologies, many electronics products now require lesser voltage and current ratings. A typical AAA battery is of the rating of 1.5V and 800mAh. These are usually used in the applications of small alarm clocks etc.
D batteries
These were common in the old days and are quite huge sized. Also known as the flashlight batteries, these again have the same rating as that of the AA batteries or a little higher. They are quite obsolete now.
Button batteries
Button batteries are the cheapest and the most low rating batteries one can find in the market. These are generally used to power up small calculators,watches etc. They have a wide variety of ratings ranging from 1-3V and current ratings of 30-500mAh.
How do I choose the right battery!?
Now that we know a little about the different kinds of batteries out there, its time to decide the right battery for the right applications. Lets understand a little about the ratings here.
Its a misconception that choosing the right voltage is enough to power up an electronic circuit. This is not true! the most important factor is the current. If an LED requires 2V to light up, does it mean a battery will continously light it up forever!?. A battery is limited not just by the voltage but also by the current. When we say that the battery is low on voltage, it actually means that its capacity is lowered. That is, at the same initial voltage, it can no longer supply the same current.
That said, lets look into some basic requirements.Lets scale the batteries on a typical situation of lighting up a LED.
As described in the arduino section about LEDs, they usually require around 2V of forward voltage and 20mA of forward current. Let us consider a similar LED requiring around 1.5V and 5mA forward current.
Now, when we read a current rating on the battery as mAh, it means that the battery can supply that much of mAh in an hour.
so, if we power up an LED @1.5V and 5mA from a AA battery, the LED will glow for 1100mAh/5mA =220 Hours!
If we power the same LED from a button battery of 1.5V and 30mAh, the it would last just 6 Hours.
Though this is not the right way to just decide upon a battery, for a person who is starting out with electronics, this is fair way of calculating the right requirement of the batteries.
Its a misconception that choosing the right voltage is enough to power up an electronic circuit. This is not true! the most important factor is the current. If an LED requires 2V to light up, does it mean a battery will continously light it up forever!?. A battery is limited not just by the voltage but also by the current. When we say that the battery is low on voltage, it actually means that its capacity is lowered. That is, at the same initial voltage, it can no longer supply the same current.
That said, lets look into some basic requirements.Lets scale the batteries on a typical situation of lighting up a LED.
As described in the arduino section about LEDs, they usually require around 2V of forward voltage and 20mA of forward current. Let us consider a similar LED requiring around 1.5V and 5mA forward current.
Now, when we read a current rating on the battery as mAh, it means that the battery can supply that much of mAh in an hour.
so, if we power up an LED @1.5V and 5mA from a AA battery, the LED will glow for 1100mAh/5mA =220 Hours!
If we power the same LED from a button battery of 1.5V and 30mAh, the it would last just 6 Hours.
Though this is not the right way to just decide upon a battery, for a person who is starting out with electronics, this is fair way of calculating the right requirement of the batteries.
Rechargeable batteries
Rechargeable batteries are the most used in hobby projects for obvious reasons. These batteries come with a wide variety of ratings. The eye-catching factor is the current rating which is quite high compared to its equivalent AA battery. These batteries can power the same application of that of AA batteries by a factor of almost 2-3 times!. The best part is they are reusable. Charging of these batteries require no big circuits. We just need to supply approximately the same current as that of its rating for the same amount of time as mentioned.
That is a 3V 3000mAh rechargeable battery can be charged by a 3V 1A adapter for 3 hours. A charging adapter can be made very easily and a tutorial shall be done on that soon :)
That is a 3V 3000mAh rechargeable battery can be charged by a 3V 1A adapter for 3 hours. A charging adapter can be made very easily and a tutorial shall be done on that soon :)