What happens to regenerative energy with no battery connected?

1

Hi all,

I’ve built a small cart powered by two hub (BOT) wheels, each driven by its own ODrive S1. The system is normally powered by a 24 V Greenworks Li-ion battery (link). Regenerative energy from the wheels is fed back into the battery.
However, I’m curious what happens when the battery is disconnected, but the cart is still moved (pushed by hand), causing the wheels to spin and generate energy.
Where does the regenerative energy go in this case?
Is it potentially harmful to the ODrives if there’s no sink (like a battery or brake resistor) for that energy?

Thanks in advance for any clarification or advice!

2

The current caused by back-emf will flow through the FET body diodes into the main system bus, with a voltage roughly equal to the motor’s speed constant times the motor velocity. Generally as long as the total current draw from the rest of the system is less than around 5-10A, this should be safe.