The math looks right from here.
Mini-guides: Force Field Defenders, Blasters, Market Self-Defense, Frankenslotting.
So you think you're a hero, huh.
@Boltcutter in game.
Yup, looks right. The "total recharge method" works great, although I like to rearrange the variables a little bit to answer the question: how much faster does this recharge with X Buff up:
B = Time to recharge if the buff were up for the whole power.
R = Time to recharge without Buff.
D = Duration of the Buff
Reduction in recharge duration: R*D/B-D
That is the amount of time it would take for the percentage of the recharge time covered by the buff to be covered without the buff, minus the duration of the buff (that is the time actually covered for that percentage of the recharge).
B = 1500/4.0875 = 366.95
so the reduction in recharge duration is: 485*60/366.95-60 = about 19 seconds which agrees with your calculations.
I find this formulation to particularly useful when trying to answer how much faster the Force Feedback proc will make powers recharge.
Draggynn on Virtue: lvl 50 Storm/Psi, 1389 badges
Draggynn's Guide to Storm Summoning(Gale-Tornado, updated 6/25/2011)
Avatar by Wassy full reference here
Leo, you're such a nerd 
I love all the nerds that make it easy for me! You guys are my cheat help!
@MARTy McFly
Thank God you guys are hear, i was so bad at maths but thankfuly exelled at Ingish. I look at yur numbers and all i see is gobbliedeegook and im not ever gonna be able to comprehend what it is yur talking about but i do apreciate it.
few! i can spel!
My character has 208.75% global recharge from set bonuses and Hasten. I want to calculate how long it will take for Geas of the Kind Ones to recharge; by default it takes 25 minutes (1500 seconds). If I recall correctly, it's: 1500 / 3.0875 = 485 seconds = 8 minutes and 5 seconds.
Except Geas itself is a 100% recharge buff, so for the minute it's active, I have 308.75% global recharge. This is where I'm likely to screw things up.
For the first 60 seconds, I have 308.75% recharge, so 60 * 4.0875 = 245.25 "recharged seconds" passed. 1500 - 245.25 = 1254.75 seconds left; then 1254.75 / 3.0875 = 406 seconds for the rest. 466 seconds total = 7 minutes and 46 seconds.
Is this correct?
www.SaveCOH.com: Calls to Action and Events Calendar
This is what 3700 heroes in a single zone looks like.
Thanks to @EnsonsDeath for the GVE code that made me VIP again!