Different Batteries connected in parallel

that is not a good idea.  especially don't do this if they are different types of batteries such as flooded, agm, or gel.  Mixing types is a real no-no, mixing the same type and different sizes and different ages will prematurely wreck your batteries as the weakest/oldest of the bunch will likely drag down they rest of the crew.

more than 3 series strings in parallel is also a no-no.  If you can, it is best to have 1 series string of batteries for their health and longevity.  this also minimizes connections and money spent on the copper to do it.

In a pinch, or if you dont have anything better, you can do it, but I would not.  If they are different types, do not put them together.  If you want a stable battery bank that will last, size it correctly, bite the bullet and buy them all at once. 

check out homepower #114 page 54 for a good article on batteries.

james - Alt-E staff