If you have access to …..
Whoops! Logan beat me to it! Another way to keep the water in the batteries that requires almost no effort is a battery water system. This trailer has batteries that are difficult to get to so I installed one. Take out a jug of distilled water, attach the pump hose, squeeze a couple of time until batteries are full. Disconnect and go on down the road.
Here's a link to the fill kit. You need the little pump listed on down the page.
https://www.amazon.com/Flow-Rite-MP2...s%2C149&sr=8-6