I’ve built the Mini Balancing Robot (see the link below) and it has been working, but I have been periodically ruining both A4988 and TMC2100 stepper drivers. I’m using two Nema 14 Bipolar Stepper Motor 5.4V 0.8A 25.5oz.in/18Ncm 3D Printer from Stepperonline and powering them with a 12V LiPo battery. I have not been using a capacitor across the Vmot and Grd wires. Could this be causing the failures?
Yes. Why not follow advice?
When I did the post, I didn’t realize the stepper motors I bought were 5.4v. Could using them with 12v also be part of the problem? They seem to run hot.
Current limiting stepper drivers like the A4988 are meant to use supply voltages above the coils voltage rating. You can read more about that in our FAQ for the motor driver. We recommend using an electrolytic capacitor because voltage spikes can cause failures without them. How are the failed drivers behaving? Did they fail when the system was first powered or after it was running for a while? Can you post pictures of your system so we can see how you have everything connected?