I realize that the OP had a BaleTraK Pro and have seen 28-29 amp on the multimeter myself, but is does seem the lower the voltage goes, the more the numbers on the monitor disagree with the multimeter.  Just wanted to point out that just because the monitor is only showing 20-22 does not mean it is only drawing 20-22A rather it could easily be 27-29A when the monitor voltage is low due to undersized wiring/poor connections.  Perhaps I should have elaborated a little more.