Thanks for the information. Our mechanic is saying some of the same things that have been said in this post. He also recommends taking the batteries out during the winter when the unit won't be used and putting them on a charger once a month. Another idea would be for us to park it in our driveway where it can be plugged in for awhile. (He didn't say how long) We know now some of the things we should do differently. It's our fault--but I will say the owner's manual didn't provide any information on taking care of batteries.