VainGlory was the first game I played that used a statistic called Cooldown Acceleration. I have played hundreds thousands of hours of League of Legends which uses a different statistic called Cooldown Reduction, so to understand it better I did a short write-up.
Cooldown Reduction is a flat, percentage reduction of the ability cooldown as a whole. This mean that an ability with a 100 second cooldown would be reduced by 1 second for each 1% of cooldown reduction a character had. In League of Legends it needed a cap because any character with more then 40% cooldown reduction would start doing magical things. See URF.
Cooldown Acceleration behaves quite differently. Because of the nature of accelerating cooldowns it has drastically lower rate of returns based on the amount that you have. Imagine that your abilities are coming off cooldown at a current rate of 100%. This makes the math the easiest. As you gain percentage points of cooldown acceleration that 100% increases. With each percentage point of cooldown acceleration, you add a point to that 100%, then the ability is divided by the whole number.
If you had an ability with a 100 second cooldown and you had 50% cooldown acceleration (summing up to 150% normal cooldown speed) you would divide the 100 second full cooldown by 1.5 (150%) resulting in 66.6 seconds of cooldown. 50% cooldown acceleration is therefore equal to 33.3% cooldown reduction. However, 100% cooldown acceleration only results in 50% cooldown reduction. The rate of return has already halved. The first 50% gave you 33.3% cooldown reduction, the second 50% only gave you 16.6% cooldown reduction. These diminishing returns are outlined further below:
| Base Cooldown | Cooldown Acceleration | Equivalent Cooldown Reduction | Difference | Cooldown |
| 10 sec | 0% | 0% | 0 sec | 10 sec |
| 10 sec | 25% | 20% | 2 sec | 8 sec |
| 10 sec | 50% | 33% | 1.33 sec | 6.66 sec |
| 10 sec | 75% | 42.8% | 0.95 | 5.71 sec |
| 10 sec | 100% | 50% | 0.71 | 5 sec |
| 10 sec | 125% | 55.5% | 0.56 | 4.44 sec |
| 10 sec | 150% | 60% | 0.44 | 4 sec |
While this is probably information that people already knew, I was hoping someone would find it useful or educational. Thanks for reading!
For funsies, the most cooldown acceleration you can have would be six Clockworks, which would be 300%, giving you 75% reduction on your cooldowns. You’d be able to use Glaive‘s Afterburn every three seconds, which would be helpful because you wouldn’t have boots. It would also be doing 610 damage. You would run out of energy. Probably.