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I am trying to build a robot using a kit I got from amazon: https://www.amazon.co.uk/DFRobot-Tank-Mobile-Platform/dp/B014L1CF1K?th=1 (it uses plastic motors).

The main problem that I am having is that whenever I try to apply a battery with 9 volts to one of the motors it only moves the slightest amount. I am not sure if the voltage is too low or not because in the manual it is using 7.4 volts.

The motors are connected up to a motor driver, here is a diagram of what it looks like

enter image description here

Could the motors potentially be broken? (Hope not because it means I will have to dissect the whole robot)

The motors I am using look like this: enter image description here

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    9V batteries are utter junk.
    – Majenko
    Oct 11 '20 at 11:16
  • Could you try to use 2 Li-ion battery (like 18650)? They will give you 7.4 - 8.4V. Oct 12 '20 at 5:05
  • @AleksejVasinov Isn't that going to give less voltage than the current battery that I am using though? Oct 12 '20 at 15:57
  • In specification it is written - "Working Voltage: 3-8V DC". So you should be good :) Oct 13 '20 at 6:43
  • @AleksejVasinov One thing I tried doing was connecting one of the motors up to the 9V battery and this seemed to only nudge the motor forwards slightly (almost nothing). So could this mean its the motor that is faulty? Oct 16 '20 at 20:03
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9v batteries are incapable of supplying enough current for a motor; their best application is tiny-current, standby devices like smoke detectors. You need a power supply that can deliver much more current than the 9v brick can. 6 AA cells in series would do much better. 6 pairs of AA-cells would give you longer run time (each 2 cells in parallel; the 6 parallel pairs in series). You could accomplish the same thing using AAA-cells if your project values space over run-time.

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  • 6 D-sized cells would be better yet. Those provide both a large peak current and a large amount of power (measured in amp/hours.) Those are large and heavy, however.
    – Duncan C
    Oct 11 '20 at 12:38
  • @DuncanC the robot's width is about 20cm. It could still work though. I might be able to find a way around it Oct 11 '20 at 18:33

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