Start Battery as Deep Cycle.......

[Scott T-Bird]

I agree Sh!t happens no matter what ... The reason I like the DCP is that it gives me the ability to operate 2 battery banks at the same time independently. The 1-2-B doesn't do that. The DCP is also a very simple ON and OFF switch. Basically, I never use it in COMBINE, just as you would never use yours in BOTH. Turning mine to ON is no different than turning yours to 1, except that my start battery is also operational without being run down by the house bank.
The only negative that Stu can point to is that I can't turn off my house bank and turn on my start batt. He thinks that it would be a crisis if I ever combined the two banks. I say that there is no crisis if all I need to combine them for is to start the boat when the start batt is discharged (not that I know how that would ever happen). If I had a situation where the house bank is actually damaged to the extent that I have to rely on the start batt for more than just starting, then to avoid combining the good and the bad banks, all I would have to do is pull the cables off the house bank. This I don't consider to be such a hard thing to do. I think I can manage that in a crisis. Then I am operating the auxiliary without combining to a bad house bank. What if my start bank fails (as in it can't be revived) and it's not possible to start the engine in COMBINE? I might have to re-wire in that event - I'm prepared for that possibility. It wouldn't be the end of the world. There will always be some remote chance for a truly catastrophic event, isn't that how we live 100% of the time?
All-in-all, I think the DCP switch is a simple ON-OFF switch and just as reliable as the 1-2-B switch. All the perceived problems with the DCP switch are remote, in my opinion, and just as easily resolved.

 

[Scott T-Bird]

If all you did is over discharge then yes it won't be a bad situation but if you really over discharged a large bank and combine it with a much smaller one you still may not have enough left over to actually crank the motor. In that case it would be best to isolate the larger bank then start the motor.

I can't think of a reason to combine the smaller start batt with the larger, discharged house bank to start the engine. If the house bank is fully discharged, I would still turn the switch to ON and the start batt cranks the engine without combining with the discharged house bank. The only reason for combining banks to start the engine would be when the smaller batt is discharged and the larger house bank is charged. If the smaller batt is actually shorted, then I can understand the need to re-wire is a PIA, but the chance is remote and not the end of the world. If my boat was actually set-up for long periods of cruising, I would probably see the reason for changing the switch. But for now, I don't see any disadvantage with the DCP, when it is recognized for what it is.

 

[Ron20324]

[QUOTE="...I can't think of a reason to combine the smaller start batt with the larger...[/QUOTE] c

There lies the point, Scott. It is for the reasons you CAN'T think of that you plan your sytems to get you going. I don't know why you'd pull cables off- just pull the batt fuses. You DO have fuses on each batt, don't you??? That's where i like my Beneteau. One on-off switch for each battery.

 

[Scott T-Bird]

Yes, a fuse on the house bank side and a fuse on the start batt. Going back to the original post, I find it hard to imagine not noticing that the batts were wired incorrectly. The first thing I do after the boat is launched each spring is make sure the batts are wired correctly. I guess that is because I find each spring that they aren't. I think the addition of ACR, batt monitor and alternator output running back to the house bank left them confused. I'm sure they never saw many boats with a 1-2-B switch or anything similar.
That's just as well ... it kept me from getting lazy, I think. We'll see how they do this spring in a new yard. I suspect they will put everything together as they found it. I can't image leaving the dock with my boat for the first time each spring without making sure the electrical system is put back together correctly.
My point about the DCP is that it functions exactly as I want the system to function. I prefer the start batt to be independent from the house bank. I don't have to switch from bank 1 to bank 2 for any reason - I just turn my switch ON. The occasion for an event such as a battery short is just too remote to be concerned about. The start batt is my auxiliary and if there were ever any reason it has to be isolated, then the mechanics of isolating the auxiliary batt are so simple, that it isn't worth needing a switch to do it. If I can't operate the start batt independently from the house bank (and the 1-2-B switch does not give you that option) I simply don't want it. I agree that 2 separate ON-OFF switches provide the functionality that I would prefer.

What set me off on this topic was Stu's misleading statement that the DCP switch combines a good batt bank with a bad bank. Well, it simply doesn't if you don't want it to. You have to set it on COMBINED to do that. The 1-2-B switch does exactly the same thing when you set the switch to BOTH. So why not complain about that?