How to have rigid-bodies and charge fields interact? Using the answer in "Why don't effectors effect effectors?", it is possible to have rigid body objects interact with each other using force fields. However, I would like to do something similar using charge fields.

If I try using this approach with the charge fields, there does not appear to be any forces applied.

Is it possible to use charge fields with rigid objects? If so, how is it done? 



Example:

The animated result using force fields in Blender 2.76:



This is created using rigid body physics. The cage is a rigid body. Each sphere is a rigid body. An empty is parented to each sphere. Each empty has a force field assigned as shown below.



If the force field is changed to a charge field, the spheres end up on the bottom of the cage.
It would seem that there is a paradox going on in the (blender) physics...

from the manual

"Charge
It is similar to spherical field except it changes behavior (attract/repulse) based on the effected particles charge field (negative/positive), like real particles with a charge. This mean this field has only effect on particles that have also a Charge field (else, they have no “charge”, and hence are unaffected)!"

Unfortunately this means that charged objects will only affect other charged objects and that giving an object a charge (force/field), turns it into an effector, and therefore does not affect other effectors...

With the field added to an empty, the field will have no effect on the uncharged spheres.

Seems like a bug/glitch/oversight/unintended consequence of the negation of the effectors affecting each other.