@drummerscott, I'm using the 250s/Smartpass combination in my 2014. Some thoughts:
- your perception of the role each plays
above isn't accurate. The distinction between them is the 250S is essentially a DC
C "smart" charger and the Smartpass is a slightly more intelligent version of a classic aux battery charging relay. The 250S "pro" is it can output suitable charging voltages for all charging cycles, even if it is receiving a low-ish voltage from the alternator; the 250S "con" is that it is current limited . . . only 20A max output. The Smartpass on the other hand can pass 80A (even higher for intermittent periods) but is really only passing whatever voltage is provided from the alternator.
The value proposition to using the combination is getting high-current bulk charging from the Smartpass and quality "smart charging" from the 250S at absorption and float cycles. And the 250S can conveniently (and compactly) act as your solar controller.
- you can place both the temp sensors (one from Smartpass, one from 250S) on the same single battery. This way, they have same temp intelligence. Pick a "representative" one of your two batteries and put both sensors there. Not crucial . . . with a well done charging system, and both batteries in same/similar location, their temps are likely to be the same. In my case it was much easier (in terms of running wire) with both sensors on one battery.
- your ground wire gauge can be small from Smartpass/250S to gnd. The charging currents are not moving through these wires; its only the supply V for the CTEK electronics.
- ideally run the main wire from alternator directly to Smartpass (as shown on your diagram) and bridge that to the 250S via the bracket things provided by CTEK. It will function with the wire going to 250S and bridged to the Smartpass, but you're needlessly moving high currents across the (relatively) smaller sq mm of the CTEK bridge bracket things.
- the CTEK Battery Sense product is not designed for RV house system use in my opinion. Personally I find the Trimetric systems a bit dated and klunky. I suggest you consider a Victron BMV-700 monitor: $160-ish, small, robust functionality. I really like mine.
- in theory, three 100W panels could output >16A in perfect sunlight. Unlikely no doubt, but perhaps consider a 20A rather than 15A CB or fuse on the main wire to panels.
