MS, I've been waiting for your commentary regarding this type of switch. I installed this DCP type of switch on my boat a few years ago to replace the old switch, which had a cracked case.
Scott,
Pro's of the DCP:
#1 Simplicity - This is a very simple ON/OFF switch with a "BOTH" feature. Does not get any easier.
#2 Isolates Starting Battery - This can prevent equipment "drop out" on boats with small house banks when the house bank previously got used for starting. As the house banks get larger the drop out of equipment is a non-issue. These were originally designed for fishing boats who start and stop the motor multiple times per day to to prevent the fishing instruments from re-setting. These boats very often have equally sized house and starting banks. The switch can work well in this application whether you have a sailboat or power boat with equally sized small banks..
Drawbacks To The Dual Circuit Plus:
#1 The DCP switch lacks the ability to properly isolate a failed bank and take it off line while using the "good bank".
#2 Lacks the ability to use the house bank to power starting and house loads while isolating the "start" bank from the rest of the system.
#3 Lacks the ability to use the starting/reserve battery to power house and starting loads while isolating the "house" bank from the rest of the system.
#4 Lacks the proper instructions for wiring configuration with a large house bank (cruising boats) without re-wiring the alternator output. Connecting it via the factory diagram, to a large house bank, will cause relay cycling. As such the alternator output needs to be re-wired to go direct to the house bank when the banks are unequally proportioned..
Blue Sea offers a technical brief on this here:
Prevent Relay Cycling In Battery Combiners
Sadly they don't include this tidbit in the installation instructions so may boaters install them incorrectly for the application.
#5 With a bank failure, such as an internal short, it forces the user to use the "BOTH/COMBINE" feature and combine a good bank with a failed bank. This can leave a boater dead in the water as it did for one of my customers as recently as last summer. That customer has since switched back to a 1/2/BOTH/OFF with a second ON/OFF for engine start isolation. It is more complicated, as he has two switches to turn ON & OFF, but he has more comfort in knowing he has redundancy and full isolation without the need for using the "BOTH/COMBINE" feature, the same feature that left him dead in the water.. While these failures are rare they can & do happen. Short of re-wiring the system, when a battery dies, you have no way to isolate a bad bank.
#6 Most boats already have a perfectly good 1/2/BOTH/OFF switch and the addition of an ACR or Echo Charger will get you the same seamless charging benefit without having to drill more holes in the boat, spend more money or to have less redundancy and isolation.
#7 With the addition of two ON/OFF switches in the battery compartments, not to be seen by vessel occupants, the DCP switch can become quite good because you now have the ability to isolate the bad bank. Create a charge bus on the load side of the hidden house bank switch and you now have a very good solution...
As I have said before for your application the switch will work just fine as it is. Your banks are nearly equally sized. While you do give up the "isolation" and "use choosing" ability, if all goes well you'll be fine and you have no reason to rip it out. For most boaters they work perfectly I just think it is important for everyone to know the pro's and con's of these switches. Blue Sea certainly is not going to tell you these things...
I do install them on center consoles and fishing boats but tend to shy away from them in deep cycling applications such as sailboats..
Hope this helps.. I'm in a rush so I am sure I forgot a few points but these should be the key points.