No, grenades aren't "weapons", they are "apparel"

Pretty much consider them as back up weapons.. their weight tends to limit how many you carry anyway.

So tend on a pure explosive / melee / unarmed build to carry between 10 - 20 grenades ( imagine them on a bandoler. )
Then between 5 - 20 mines in the backpack.

On a gun build 3 - 6 grenades just in case or for tactical advantage.