If you search the threads you'll find some good information. Your 170W solar
array is probably just big enough where an MMPT controller is worth the money
... but it depends on ambient temperatures... and opinions vary about the efficacy of MMPT controllers. I have the same battery setup as you, with 216W of solar panels
, and I use the Blue Sky 2512ix (MMPT). I monitor charging
with my existing battery monitor. It shows the solar
panels' full rated output going into the batteries with any kind of sunlight... can't ask for more than that.