A small exception with converter on, that could confuse, is when batts are now full at 14.6 volts and you dial down the adjustable voltage to 13.6 volts. For a little time my Trimetric shows a small negative amps while battery voltage falls until it gets to 13.6 and amps go to zero and small positive back and forth, where it stays.
I have not zeroed the Tri, so after a long time on shore power with batts floating it shows hundreds of positive AH accumulated. Have to reset the counter when leaving on a trip.