Half a gallon is a lot of water. Your battery must have been dry. My thoughts. If the battery had been left in a discharged state for a long time it will not be in good condition and charging it when dry, it is probably dead. I doubt that a Kiwi would have a smart charger, but it may. I would get a portable smart charger that had a desulficatin??? (sorry bad spelling) cycle. That may revive the battery, but I think you will need a new battery.
A few notes. When you fill a battery add water until the water in the cell looks like a cat's eye. Disconnect the battery when your not going to use the trailer there are drains on the electrical system even when you are not using the trailer.
No I am NOT retired. I work full time.:D
Tracy from Central PA
2010 Jayco 17Z Ex-Port
2004 Ford Explorer V8 with the tow package
2010 Camping Stats
Nights Camping 132 - Nights Camping in My Z 102
2011 Camping Stats
Nights Camping 107
2012 Camping Stats
Nights camping 133 - Nights camping in my Z 128
2013 Camping Stats
Nights Camping 66 Nights