If your converter is not up to modern Smart standards I'd upgrade by replacin the "Guts" (electroncs) with a Progressive Dynamics 4600. or if it is a stand alone 9200 (the difference is mostly packaging)>. I just had to replace my 9180 (I have the charge wizard)
No better way to keep 'em charged
For back up (I had to swich to back up) a Battery Tender. the model I have is 1-2 amps "Tender" 20 amps "Boost" (Must be manually initatied) and 70 anps Jump Start (likewise) it took 24 hours in boost to re-charge my system when the old 9180 died 9 days ago