I am replacing my house and starting batteries on a 36' sailboat and was ready to buy a pair of the 12V 230Ahr AGM Super Cycle batteries for my house bank as they will fit perfectly in my 4D size tray if they are installed on their small sides with the long dimension becoming the vertical height.
The dealer I wanted to purchase from said these cannot be installed on their side "...you have to lie these down in the way they are designed, you cant stand them upright. They are heavy and the plates hang from the top side so when you mount them vertically their weight is inadequately supported and prone to breakage in the event of a bump in the road or a wave in the ocean. The same thing applies for all lead acid batteries but the bigger the battery the more the effect will occur."
I can understand this in a Jeep or or perhaps a fishing boat smacking through chop at 25 knots, but is there enough stability in a slow cruising 36' sailboat and mounted amidship that this would not be an issue? I was a bit surprised to hear this and wanted to find more opinions on this.