This robot use two power source, one for the Raspberry Pi and one for the L298n Motor Driver.

For the raspberry Pi, I use two kind of USB battery Pack. 

1. One with the big size has the capacity for 10.000 mAh with two output for 1 A and 2 A. with this battery Pack I can turn on the raspberry pi for 8-9 hour straight. but the problem here is the size for the battery pack is too big. On my not so big chassis, I need to forcely fit the battery pack, and the result was not good

2. The second one is a smaller one with the capacity 5600 mAh and has one output for 1 A. Surprisingly the whole size of this USB battery pack fits perfectly to my chassis. It has shorter time to turn on the raspberry pi (4 hour) but I think its enough.

For the L298n Motor Driver I use AA baterry with the minimum voltage of 6 V:

1. First I use a pack of 4 AA alkaline battery that give 6 V to the motor driver module. Using this pack the wheel of the robot runs perfectly stable because the motor driver give 2 A current which is sufficient to make the robot walk normally. But again the size for this battery is too big for the chassis, and after 1 hour controlling the robot, the battery run out of power and I have to change the battery again and again.

2. Later I use AA 3,7 V UltraFire Rechargable Battery. For this battery I only use two pieces and it already give me 7,4 V for the motor driver module. Since the module can receive voltage up to 12 V,  I don't need to add a power regulator. Because it only use 2 pieces battery, I can fit this battery pack anywhere I want in the chassis. It can make the robot run longer than the previous one for about 2 hour run time. And everytime it run out of power I just need to recharge it again