How are cooldowns calculated?
I know there are other questions about power recharge and weight, but none of them (that I found) ask or answer this.
At first, I assumed the X% modifier to recharge speed actually meant your recharge speed is (100+X)% the standard value
. That made sense, because the modifier could positive or negative. Then I realized your recharge speed modifier can go all the way down to 200%, which completely invalidates my assumption.
So, what the hell do they mean by 200% Recharge Speed? I understand it’s a bad thing, but I want to quantify how bad it is. Given a recharge time of 5 seconds, how is this 200% supposed to affect me?
One Solution collect form web for “How are cooldowns calculated?”
Mass Effect tracks cooldowns differently than in most games. Rather than mapping increases / decreases to the base cooldown of the power (where a 100% reduction would be no cooldown), it increases / decreases the number of uses per second.
The Theory is as follows:
Assuming a 5 second cooldown at +100% cooldown would be twice every 5 seconds, or 2.5 seconds, and +200% would be 1.67 seconds.
Reverse would work the same way. 100% cooldowns means once every 10 seconds, and 200% cooldowns means 15 seconds.
!!Science!! Follows:
I decided to pull some numbers from my finished ME3 playthrough save, my Vanguard.
Notes on the Numbers:
 I respeced Shepard, clearing all skills.
 I still had one of the research options for 5% power cooldown.
 All testing took place on the Normandy, which meant no power cooldown gear was applied. I switched my gear to damage or shield bonuses instead, just to be safe.
I have 3 setups for Weight Cooldown Bonuses of 200%, 0%, and 200%.

200%: Javelin Sniper Rifle and Claymore Shotgun.

0%: AT Raider Shotgun and Locust SMG.

+200%: Phalanx Pistol.
And here were my numbers. I’m using the skill “Pull”.
With the 0% loadout:
 3.81 seconds
 3.08 seconds (+25% from Rank 2)
With the +200% loadout:
 1.31 seconds
 1.21 seconds (+25% from Rank 2)
With the 200% loadout:
 11.8 seconds
 10.8 seconds (+25% from rank 2)
Other Values: 1% total CDR: 4.07; 0% total CDR: 4.00
Pull has a base cooldown of 4.00. Following our Hypothesis, 200% cooldowns would give a cooldown of 12.00 seconds. Our 5% CDR has a cooldown of 11.8! That’s pretty close to the expected!
Math confirms that this is, in fact, correct: 4 (1.00 + 1.95) = 1 / 11.8!
Additional bonuses, like rank 2 of the ability, stack additively. 1 / 4 (1.00 + 1.7) = 1 / 10.8!
So this works fine and dandy when your malus is a penalty, but what about when you have a bonus? Bonuses are a bit easier – simply divide the cooldown by the bonus %, converted to a decimal.
4 / (1+2.05) (from our 205% weight + research bonus) = 1.31
4 / (1+2.30) (from rank 2) = 1.21
If you have a net bonus, formula is:
[Old Cooldown] / (1+ [Percent Bonus As Decimal]) = [New Cooldown]
If you have a net penalty, formula is:
[Old Cooldown] * (1+ [Percent Bonus As Decimal]) = [New Cooldown]
It’s late, so if someone wants to check my math / make a pretty picture with the formula / math markup, please, be my guest.