Your line-avoiding robot is otherwise great, but it can be a bit of an annoyance to run after it while you’re holding the USB cable. It’s time for your robot to get its very own power source.
We can’t use a regular 9-volt battery for the bot, as it doesn’t have enough juice to power motors, the LED, and the NeuroSky dongle. It’s also much nicer to use a high-capacity rechargeable battery, because it can keep your robot running 10 times longer without the need for a battery change.
We used DualSky 1300 mAh 30C 2s1p 7.4 V battery (Figure 2-11). What do all these values mean? 1300 mAh (milliamp hours) or 1.3 Ah is the battery capacity. Higher value means longer running time. 30C is the discharge capacity for one hour. In this case 1300 mAh * 30 = 39000 mAh = 39 Ah. 2s1p means that battery has two 3.7 V cells in parallel. So together they give you 7.4 V, the output current. The recommended input voltage for Arduino Uno is 7–12 V.
Figure 2-11. Rechargeable lithium-polymer battery pack
Always use strong batteries carefully. Acquire and follow battery-specific instructions. A short circuit can lead to heating, fire, or even explosion.
Batteries often use one set of cables for charging and other for discharge (powering your device). In our battery, the blue connector is for discharge and small ...