I have a 1999 model 24/1800 installed charging 4 house batteries. It charges fully, say to +48 amp hours, then shuts off. The batteries then start to discharge. If I unplug and replug from shore power or turn the unit off then on, the charging resumes at least for some period of time. Is this normal behavior? Since we are running often I have not been able to wait long enough to see what happens if the battery discharges enough to determine if the charger will restart. Any thoughts? thanks