since people normally don’t pick-up EMP cells, it also took me a while to figure out were to find the ultracapacitors 4 making the Experimental Messuer Rifle ammo, 
now you know also
All EMPs provide this ressource now.
Additionally they minimum recycling amount was reduced from 10 to 1.
I always gathered them since the companion update to get enough rubber for my prefered armor.
Someone mentioned, that Car battery EMPs don’t provide this ressource yet, but I didn’t check it yet.
large EMP cells 30, medium EMP cells 20, small EMP cells 10, nope for the car battery
there is a skill that helps machines drop these items more often
I always collected the batteries to use them against large machines, it helps a lot if you can get close enough. And it’s faster than a bazooka emp shot. Now I almost feel bad taking them apart.