How does KerbalEnginer/Mechjeb calculate deltaV for mixed massless/massed propellant engines?

[MatterBeam]

Hi.

While designing an engine mod, often I've had the idea of creating an engine that uses a regular propellant (liquid fuel, intakeAir) alongside a massless 'propellant', such as ElectricCharge.

How do Mechjeb or KerbalEngineer calculate deltaV in that case?

Is there a workaround if they can't?

Is there a way to create some sort of Generator module with its consumption of a massless resource tied to that of the propellant flow, outside of an Engine module that Mechjeb/Kerbal Engineer reads?

[Kerbart]

Propellant, by definition, has mass. However, as a "fuel" (energy provider) it can certainly exist. So I assume what you mean to ask is: how do MJ/KER account for the amount of electricity available to provide for propulsion? So if you only propellant for 5 minutes of burn time, but only electric charge for 2 minutes, the amount of DV available would be, say, 200 m/s and not 500 m/s?

I don't write mods but I suspect inspecting the available charge in the batteries will go a long way.

[sarbian]

No, MJ assumes a infinite amounts and I am quite sure KER does the same.