Joe,

21.8V for 30 seconds is not too low. The 30 second timer would only be affected by a fairly heavily loaded battery. That voltage must not rise above that for the full 30 seconds. A better AGS trigger would be based on state of charge. SoC takes the varying load affected voltage out of the equation.

You might be surprised what the resting voltage is on a battery drawn down to this voltage due to a heavy load.