powering line follower mobot

The line follower i made follows the line accurately. We have a 10m track, my problem is it follows the line in 1 round only and after folloing the line it does not function as desired. I have to charge the battery again so that the mobot will functions as desired. Can you suggest on what to do? should I put a buffer before supplying it to the system? or voltage regulators such as LM2940 or add a battery and use 7805?

I would suggest a higher voltage battery and an LDO regulator, with the motors fed from the unregulated side. However, you will have to change your H-bridges for this.

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pls help me for my mobot using microcontroller pls...

i see 4 1.2v Ni-MH Batteries but no mAh rating. Maybe its too low. Ive seen some with a mere 1000 mAh and if so it would die pretty quick i assume. Think about battery mAh also.