I did it your way for 20 yr., mix-match of panels I'd come across over the yr. No problem. However, as the previous person said, you won't see the rated output at the charging end. Couple yr. ago, I decided to upgrade to a couple MX60s, add a few more panels. I ended up rewiring my entire array into 36 v. strings [formerly all just left at 12 v] and run them all into a combiner box. Then, two circuits out at 36 v. to the controllers, 12 v. out from them to the batteries. Much, much more efficient and equal to adding even more panels. Of course, the controllers cost, too. For what you are doing now, however, you should have no problem. If your system grows, and your usage needs increase, at some point it will make good sense to change things around with an MPPT and etc.