The base recharge of energy at level 1 is 3 minutes (180 seconds).

My suggestion is that every '50' ranks, the meter increases by +.5 (so at level 50 you'd recharge 1.5 per tick), but you also get a timer 'adjustment' of 30 seconds -- so unbuffed you'd have a 3 minute and 30 second recharge for '1.5' energy.

rank 50 -- 1.5 en @ 3.5 min (easily you can reduce this by 24 at this rank (+6 rechargers) so 1.5 en @ 3.1 min)
rank 100 -- 2 en @ 4 min (easily you can reduce this by 48 at this rank (+12 rechargers) so 2 en @ 3.2 min or better)
rank 150 -- 2.5 en @ 4.5min (easily you can reduce this by 72 at this rank (+18 rechargers) so 2.5 en @ 3.3 min or better)
rank 200 -- 3 en @ 5 min (easily you can reduce this by 96 at this rank (+24 rechargers) so 3 en @ 3.4 min or better)
rank 250 -- 3.5 en @ 5.5 min (by now you will 'probably' have +30 rechargers) so 3.5 en @ 3.5 min or better)
rank 300 -- 5 en @ 6 min (only 1-4 people here so who knows what rechargers they'll have) 5 @ 3.6
rank 350 7 en @ 6.5 min 7 @ 3.7
rank 400 9.5 en @ 7 min 9.5 @ 3.8
By implementing this, you will be rewarding people for reaching the '50 increment milestone' and find the solution to the problem of 0 recharge that is approaching. The pattern is completely predictable too so people can plan out their energy cost/use ratios.

Rank Number of Seconds New (energy) Old (energy) Recharge (using the rechargers suggested) Differential
1 180 1 1 0
50 186 1.5 1.19 + .31
100 192 2 1.5 + .5
150 198 2.5 1.8 + .7
200 204 3 2.43 + .57
250 210 3.5 3.5 + 0
300 216 5 6 + 1
350 222 7 18.5 -10.5
400 228 9.5 Infinite Recharge Rate as charge is down a negative number - Inf.

Note that this would 'buff people' a bit but would even out at the max items versus what happens currently at 'rank 350/400 scenarios'.

the overall concept isnt that bad, but it can in no ways be based off rank. CCers will be invincible. Now adding 30 seconds +1energy per tick for every new level of relays you research and equip 4 of them is another thing. Add like a "Set bonus" as they call it in WoW.

"Plasma RelaysX4, Time to next Energy tick is increased by 60 seconds, Energy per tick increased by 2."

Skipping the first set of relays because +1 charges are not worth adding 20 seconds too IMO.
(Im trying to do the math when I do do it for this ill edit in a graph.)