You can use the Sphero bluetooth API to write the appropriate command yourself into the node.js SDK.
The bluetooth API is at: https://github.com/orbotix/DeveloperResources
The command you would send is the SetOptionFlags command (35h). You send the id byte of that command, followed by the payload, which is a bitmask. Set the first bit.
I will warn you, though, that this isn't supported behavior. The battery can completely die over a long enough time in the charger.