Sions Ult

How low is his cooldown with no reduction at level 17??

I just finished a game where the other teams Sion ulted THREE TIMES!! in 1 team fight that lasted a little over 1 minute maybe 1 min 20 seconds at the most while defending our base.

He opened the fight with a ult....then ulted during the fight,........then a 3rd ult which won them the fight. other team had a Lux and even she didnt ult this often.

Now he did have %30 reduction from items and ultimate hat but still to ult this many times in 1 fight his ult cooldown must already be low. I dont play him so i have no clue which is why im asking.