Troubleshooting Voltage to Motor. Motor Driver vs my electrical knowledge?

We recently started building a mecanum car, starting with this kit:

We are using an Arduino Nano, an LM2596 Buck Converter, 2 DRV8833 Motor Drivers, a LiPo 2S 7.4V 5200Mah 50C battery, and a RadioLink T8S

The DRV8833 is not the exact one that is in the Fritzing diagram


The Fritzing Breadboard Diagram:

Everything is working just ok. The car can be driven by the remote and the cool mecanum steering is working as intended. However, the voltage going to the motors seems way too low and this where I’m hoping for some assistance.

We are using this DRV8833 motor driver: GitHub - TheArduinist/DRV8833: A Arduino-based library for the Pololu DRV8833 dual motor driver carrier and using the non-speed option as we are just looking for On/Off at this point.

Using a multimeter, the voltage from the battery is ~7.8V and remains 7.8V at both motor drivers VCC/GND. However, the output on both OUT1/2s and OUT3/4s is only ~2.2V.

When we run a test setup with just one motor driver and one motor, we get 7.8V out to the motor.

So we’re struggling to sort out what is going on how to fix this. My electrical knowledge is very rusy, but I believe the motors are wired in parallel so they should each be getting 7.8V (which they are at the VCC/GND from the multimeter). So why is on 2.2V going to each motor?

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Hi @Snuffy2 and welcome to the forum.

If you run just ONE motor driver with TWO motors, is there a still issue? Same issue on both driver boards or on just one?

Maybe these two motors are too powerful for one board.