I ran into an unexpected issue with V2 of the DRVR.

If you look at the image I posted recently, DRVR v2 is comprised of the following:

• RVR Base
• A Raspberry Pi 4
• An Oak-D AI Camera
• An 18000 mAh battery
• Some 3D printed plastic parts and cables

When I tried to run the robot in that configuration it struggled to turn and move. After a brief period, the RVR Base started flashing yellow and orange which is an overheat warning. It then waits for a mandatory cool down period. Oops.

Doing a bit more research, the RVR Base has a maximum weight capacity of 250g. The current configuration is 550g. 300g for the battery and 250g for everything else.

Why do I have the extra battery? I knew that the Raspberry Pi and the Oak-D could consume a lot of power. Up to 5v at 3A. The battery has a 1A port and a 2A port so I could feed the Oak-D 1A and the Pi 2A.

The RVR has a USB port you can use for power, but that's limited to 2.1A. I tried running that to the Pi and powering the Oak-D from it. The RVR would run for a few steps and then eventually stop communicating with the Pi. I suspect a large power load from the base eventually caused a brown out of some sort.

To verify my software was working and to feel like I accomplished something, I ran the robot while holding the battery in my hand, and running a USB-C cable to the Pi 4 for power. Sure enough that worked really well. It did look like I was walking the robot with the USB cable acting as a leash.

I tried a smaller battery pack which was 200g. The robot worked better in that case. Still stalling a bit, but it would have a hard time with the hills in the park. 50/50 whether it would make it.

I've now got a small power supply that takes a single 18650 cell. That's down to 67g, I left that running the robot code in my office and it drained the cell in about 2 hours.

I think that will be light enough to remain on the robot and still provide enough power for the Pi 4 and Oak-D. We'll see in my next run.