I'm a bit confused abou this module. Does it only restore your energy after a kill if you're not using energy as it begins to restore? Because I seem to notice the blue highlight pulsing across my energy bar as if it's trying to restore some energy (say when I go into cloak after a kill) but it doesn't restore any energy.

Could someone clarify this please?

It refills energy but it is inconsistent. Lvl3 is full energy refill so you would figure it would be the whole bar but sometimes it isn't when shield is up.

if you still have armour on after the kill, try switching it off for a split second and you'll see your energy raise up pretty damn quickly. i usually double tap armour after i kill someone and 90% of the time just from that split second my energy will fill up to 100%.

oh and in terms of upgrades, i believe that upgrade 1 will refill 50% of energy, upgrade 2 is 75% (i think?), and upgrade 3 restores full energy after each kill.