Recharge times and Hasten downtime.

Can someone help me with some kind of formula to figure out the real recharge time for a power if Hasten wears off while it's recharging?
Like, for example, say I have Benumb from Cold domination. Let's suppose no Recharge enhancements or bonuses for easier numbers. Benumb has a base 120 second recharge. With Hasten on, that Recharge would go down to 70.6 seconds. (I'll assume it's 71 seconds for sake of easier numbers, again)

Now, let's suppose that Hasten is active, and Benumb was activated, recharged for 50 seconds, then Hasten expired. How much more time would Benumb really need to fully recharge?
Would it be something like... 50 seconds while Hasten is active meant Benumb has recharged 70.4% of it's full downtime. And now that Hasten is off, it would take 29.6% Of the original downtime (120 seconds), which would be something like 35.5 seconds. Which would make the total recharge time 85.5 seconds?

Am I shooting in the dark way off target?

Now..the more complicated version. Let's assume Benumb has two 50 Recharge IOs, which makes for a 83.32% Recharge, and a recharge time of 65.5 Seconds instead of 120 while Hasten is dead, and 47.7 second recharge if Hasten was active throughout the recharge. And then add ontop of that a 12.5% Global recharge from two Decimation sets. Which would further reduce the recharge times to 45.1 seconds and 61.3 seconds with and without Hasten respectively. (Yes, I"m aware that when calculating recharge for a specific power recharge bonuses from single IOs in the power would simply be added ontop of the global recharge. So in the previous case it's simply a case of Benumb having 95.82% recharge on it. And yeah, I know that global bonuses are simply added ontop of the value you have, and not subject to ED. So having say... 107% global recharge bonus would make a total of 190.32% recharge for benumb, not less) how would all that work out?

Honestly, my brain hurts just from typing all that lol. Never been too good with number crunching.

Any help would be greatly appreciated. Thanks in advance

I suspect you might find this guide helpful.

Thank you all for the answers. This has been very educational. Much appreciated!

A little late to the party but this is how I deal with recharge buffs active for only part of the time.

With no recharge buff 1 second of game time counts 1 seconds towards the total recharge value.

A recharge buff active in that second, multiplies that by the total recharge value.

So in the first example example given.

The 50 seconds of hastened recharges has added (50x1.7) 85 seconds to the total.
the remaining 35 seconds tick off at the baseline rate

Total recharge is the 85 seconds.

In the second example given:
At the 'baseline' thanks to the slotting and global bonuses each second that ticks adds 1.958 seconds towards the 120 required,
With Hasten up each second adds 2.658 towards the 120 required.


Mathamtically its exactly the same as the way Father Xmas presents, I have had a lot more sucess getting friends to understand when its presented verbally, rather than purely in equations.