So far, we did everything on breadboards and powered everything from the Arduino which was getting its power from the computer via the USB cable. So, basically, we did not think about power management at all.
But in robotics, we don’t want our robots or projects to be handicapped around the PC, rather we want something that’s mobile and wireless. And there comes the powering issue hence battery selection!
Battery selection for your project can be quite tricky since it will significantly affect your physical design and components and most importantly, budget.
There are quite a number of battery types available on the market using different alchemy to store energy. While they come in different shapes and sizes as well as with certain limitations depending on their storing technologies.
Some batteries are intended to last more life (charge/discharge) cycles and cheap while some batteries are designed to be lightweight and small in sizes. There is always a compromise. If a battery has a long life, the possibility is very high to have big sizes and this could be a reason to pay attention in the selection process of battery for any robotic application.
Primarily we can categorize them into 1.Rechargeable & 2.Non-rechargeable accounting their reusability. We are mostly interested in the rechargeable ones!!
Non-rechargeable(Alkaline, carbon cathode,… ):
The non-rechargeable battery category includes our most common 1.5v pencil (AA,AAA)batteries which we used to use on toy cars. They can be used to run some small motors using 4-6 together.
9V Alkalines are often used when the current requirement is not much of a concern.
But the problem with these is that they require frequent replacement which is not cost efficient at all for the long run.
Lead Acid Battery
The main feature of these batteries is that they are very cheap and durable. They are available in usually from 4,6,12 up to 24 Volts.
The major trade-off is that they are pretty heavy, which will consume much of the energy it’s supplying in a moving robot. They also take a long time to charge.
Lithium Ion(Li-Ion) These 3.7 battery cells are used in robotic applications for lightweight and high-energy density. These batteries are usually found in laptops and cameras.The batteries in our mobile phones are also the same. With stable output current, Li-Ion batteries are best suited for robots running general gear motors with bunch of current drawing sensors.
- Lithium-ion Polymer(LiPo) These batteries are kind of the upgraded version of Li-ions, having small dimensions, are lightweight compared with other types of batteries and has a very high current output. All of these features are completed with a battery boast of 3.7V on every cell, which means a high energy density.
Unlike Li-ions, they can discharge/recharge very fast but requires special charger which may cost 2-3 times more than the expensive battery itself. Trying to charge them from normal charger will damage the battery and can even lead to explosion!!!
They are available typically in 3.7V(single cell), 7.4V(2cell) , 11.1V(3cell) and so on. And the price varies due to capacity and discharge rate.
Being expensive and high maintenance, these batteries are only used in cases where the current requirement is pretty high and weight matters a lot like quadcopters and RC cars/planes.
Others: There are also some batteries like Nickel-Metal but has lower voltage per cell or you can even power your project from a power-bank(which is basically a Li-on battery with voltage regulation).
The charts below shows the price comparison of these batteries.
It is pretty clear that the best batteries, Li-POs are way too expensive than the rest while the Li-ONs provide much of the features within a moderate price range. So, unless we are making RC cars/planes or quadcopters, Li-ONs are the right batteries to go with. Then again, if we are building something non-mobile where size&weight is not an issue, we can go for the cheap lead-acid also.
Click on the images to see details about the battery specs and buying information. Also, have a look at the resources linked below to learn more about batteries and power management.
Feel free to comment if you face trouble understanding any part of this tutorial or have additional queries!