List<IMyJumpDrive> jumpDrives = new List<IMyJumpDrive>();
public Program()
{
    Runtime.UpdateFrequency = UpdateFrequency.Update100;
    jumpDrives.Clear();
    GridTerminalSystem.GetBlocksOfType<IMyJumpDrive>(jumpDrives, b => b.CubeGrid == Me.CubeGrid);
}

public void Save()
{
}

int freq = 3;
int c = 0;

bool sequentialJumpDriveCharging = false;

public void Main(string argument, UpdateType updateSource)
{
    c++;
    if(c % freq == 0)
    {
        IMyJumpDrive lastCharged = null;
        IMyJumpDrive lastCharging = null;

        foreach (IMyJumpDrive jj in jumpDrives)
        {
            if (jj.CurrentStoredPower < jj.MaxStoredPower) lastCharging = jj;
            else lastCharged = jj;
        }
        if(lastCharging != null)
        {
            foreach (IMyJumpDrive jj in jumpDrives)
            {
                if (jj != lastCharging) jj.Enabled = false;
            }
            lastCharging.Enabled = true;
        }else if(lastCharged != null)
        {
            foreach (IMyJumpDrive jj in jumpDrives)
            {
                if (jj != lastCharged) jj.Enabled = false;
            }
            lastCharged.Enabled = true;
        }
    }
}