Charlie, if you look at the online & printed materials from battery
makers, and from most of the folks in the 12v "power" businesses, you'll see a consensus that the best way to hook up batteries in MOST situations, is to make 12V banks by adding cells in series--not in parallel. Once you go to a series+parallel or plain parallel setup, you add possibilities for incorrect charging
and other problems that simply can't exist with a series-only setup.
If you read up on that, and you understand and appreciate the potential problems, only then think about these series+parallel setups, no matter what fancy charging
or monitoring gear
The simplest most robust way to go is series-only banks, and if you need more than one, you switch between banks. That also gives you some redundancy and less urgency if one cell fails and only takes out one bank. The most cost-effective way to build battery
banks is by adding 6V cells to make 12V (Sam's Club or Trojan "traction" batteries for golf carts are popular) or if you want more power, go to an industrial battery supplier where they sell single
2.2V cells for fork lift
batteries. Wire up six of those, and you'll have one whopping huge 12V bank--with each cell still small enough to lift
(well, more or less) and replaceable if it fails.
As for the series+parallel bank you've already got...well...I'd say probably leave it be, treat it as one bank and use it most heavily--so you can replace it with something better, sooner.<G>