FYI - your on-board OEM battery monitor is practically worthless so don't bother getting concerned about the reading you get from that device.
Did you check the water level of your new battery when you purchased it? When you say the water level was low - how low - were the plates showing? Even the old fashioned single voltage (dumb) converters won't significantly deplete battery water is a week or two but topping off at least once a month is a good idea.
Have the battery tested - it's free - bad cell will result in rapid water depletion.