Delay SAN shutdown on power outage, avoid corrupt databases...

In my case the SAN I have will shutdown immediatly if a power outage is detected : and this cannot be changed.
My hardware : Dell EMC AX150 + APC Smart UPS 750
You cannot delay this shutdown through the NaviSphere software.
This is really annoying since the SAN hosts the Exchange databases (could have been SQL databases too).
When there is a power outage, the Exchange server doesn't have time to shutdown before the SAN turns off.... and this can cause database or logs corrupt...
In order to avoid this and since there is nothing I can parameter, I have added an intermediate UPS as shown below :

SPA and SPB are the 2 power supplies of the SAN

So my servers (connected to another UPS) can shutdown on a power outage (please read the shutdown scripts article) and then once the intermediate UPS battery is low (or you can parameter a delay too) it behaves like a power outage for the SAN+UPS and this one turns off too.