We've built obstacle avoiding robots .
Simple spec: 2 DC motors (6V-10V), HC-04 Sonar sensor, 1 servo - based on Arduino Uno with L298N motor controller. Doing this as part of a CoderDojo group project for beginners.
Powered by two PP3 9v batteries, one for the uno, one for the motors.
Clearly the PP3s are not up to the job. The start/stop demand is too great. After a while the motors will not start , or one only will start and generally it becomes erratic. Particularly bad if using PWM to control speed. I need a better solution.
I've been reading about possible battery configurations. I've seen it suggested that LiPo rechargeables are the way to go. They seem a tad expensive and require expensive chargers too. ( and as an aside - dire warnings exist about how hazardous they are.
I could run from a single 11 volt maybe and supply 5volts, for the Arduino, off it, by regulation.
I would welcome suggestions as to what batteries/ battery configuration might be suitable.