Diamond Lances consume all stacks of Armor Charge when using Grenade Kickstart
While the grenade is fully charged with the Grenade Kickstart mod equipped, if the player picks up and then throws a Diamond Lance then they will consume every stack of Armor Charge without gaining any benefit.
If the grenade is not fully charged then throwing the Diamond Lance will not consume armor charge and will not interact with Grenade Kickstart in any way.
Incidentally the Diamond Lance is able to activate other "grenade" effects such as the Heart of Inmost Light's empowering buffs.