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Old 12-22-2015, 06:13 PM   #1
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DC System Discovery Day

Hello team!

As my introduction to our new 42’ 2000 Navigator continues, I had a chance to spend some quality time in the bilge to figure out exactly how the factory has wired this wonderful vessel. As was documented in an earlier thread, we have had a total failure of battery #3 and the other two are below 80% of rated... so they are on their last leg too. All of the batteries are currently 8D Ray-O-Vac’s from Batteries Plus (NOT deep-cycles), but will all be replaced. Let me also say that there is quite a bit of space to add multiple batteries and also vertical space. Where the #3 battery sits, there is a deck about 36x12 and where 1 & 2 sit is about 48x12.

Below is the diagram and I will point out a few of the features.



Real pic of switches (I am sitting between engines looking starboard):


Battery location (aft under cockpit, still sitting between engines looking aft)


It’s a fairly ingenious design. As it sits, each battery can be isolated for any task. Meaning, there is no “starter bank” or “house bank” designation. That frees me up to design the new system as-needed.

Charging is not tied to the battery switching. I think that is a good thing.

One thing I see as a problem is that all the alternators are tied to the starter posts. Even the genset.

Another thing I am curious about is that the two engines starters are tied together. How common this is I can’t answer because this is our first twin-engine boat. The engines are, by my standards, large, however, I am not the expert. I don’t know how much juice is needed to crank them over. Maine Sail (the guy from Compass Marine) consistently says that starting smaller sailboat engines is a breeze with a house bank, however, I don’t know if these big Volvo’s fall into that category. The instruction book makes only a couple of references to batteries. One of which says the electrolyte density, but the other says: Battery capacity for a 12V system……… 2x12V connected in parallel. max. 110Ah (total max. 220Ah), so it’s hard to say one way or another exactly what is “required” to start these gals.

Finally, the battery switches are all the way in the bilge. That is good and bad. The good is that making an error while underway is less likely. The bad is that it brings in the out-of-sight-out-of-mind mentality and opens the door to an error when anchored or access during an emergency. That may change in the future, but for now, I will just note it and move on.

Here is what I am considering. Let’s say, for a moment, that I do indeed, need to have a separate starter bank for these motors. Would it make any sense to make one bank a pair of dual purpose 12V batteries (Group 27 in parallel maybe?) specifically for that task? Part of me says yes, but unless I start switching around the switches whenever I start the motors, I would me mixing the starter bank with the other two banks. In a way, that seems pointless. But that does still leave me room for two banks of four 6V golf cart batteries (if sized from Trojan T-105s, although there is room to go with taller batteries with even more amp hours).

Otherwise, if we determine my motors do NOT need dedicated starters, could I not go 100% golf cart on all three banks? I will eventually want to put in a medium-size inverter, so the way I see it, the more the merrier.

I am not afraid to make some major changes, however, considering that this is a fairly good setup, about the only thing I might need to do other than all new batteries and a few lug changes would be to maybe move the alternator feed wires… but to where, I am not sure. Then, maybe next year, throw in some buss bars and move the switches up to the main salon. It’s not a very far move. Just a foot or so above (through the floor) from where they are in the bilge and into a cabinet below the breaker panel. Still, that would be a fairly big task that I am not really ready to tackle.

Look forward to your opinions.
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Old 12-22-2015, 06:40 PM   #2
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Are you sure your alternators for the main engines are wired together full time?

That makes no sense to me.

The other draw back to having the battery switches in the engine space is if you have a DC electrical fire you have to go down there to turn off the switches. Not very handy.

And not real safe if the fire is in the engine space.
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Old 12-22-2015, 07:12 PM   #3
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What engines ?
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Old 12-22-2015, 07:19 PM   #4
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What engines ?
6.3 turbo Volvo's. 318hp TAM 63L
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Old 12-22-2015, 07:25 PM   #5
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Are you sure your alternators for the main engines are wired together full time?
Yep... all three alternators are connected directly to the positive starter posts. While they aren't directly tied together, there seems to be one starter circuit.
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Old 12-22-2015, 07:30 PM   #6
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A single group 31 will easily start that engine. I would have a dedicated pair of 31s for each engine.
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Old 12-22-2015, 08:02 PM   #7
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Yep... all three alternators are connected directly to the positive starter posts. While they aren't directly tied together, there seems to be one starter circuit.
Your drawing seems to show the two engine alternators connected to each other at one engine. If so, and there is no isolator involved, then they are directly connected to each other it would seem.
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Old 12-22-2015, 08:24 PM   #8
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Your drawing seems to show the two engine alternators connected to each other at one engine. If so, and there is no isolator involved, then they are directly connected to each other it would seem.
Yes... That is correct. In what appears to be an attempt to only have one starter system, the alternators end up being tied together. The wire between the engines on the drawing is about a 4-gauge.
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Old 12-22-2015, 08:36 PM   #9
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A single group 31 will easily start that engine. I would have a dedicated pair of 31s for each engine.
Two for each or one for each... Or two tied together to start both?
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Old 12-22-2015, 08:44 PM   #10
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Threads like this inevitably get very confusing such as this one already has. I would get a copy of Nigel Calder's or Charlie Wing's marine electrical books and study them before jumping into anything.


Any wholesale revision to your electrical system can't possibly be discussed effectively on a forum. There are too many possible changes and too many opinions.


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Old 12-22-2015, 09:29 PM   #11
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David is right. There are a number of ways to go about this. And those books would be a big help to you in figuring out which way to go about it and how you want it to end up.

And you certainly can discuss it here if you like.
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Old 12-22-2015, 10:07 PM   #12
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One of the items to consider is that if the starters and alternators are all tied together, you won't get significant charging capacity out of all the alternators without a smart regulator setup such as the one from Balmar. The regulators tend to fight each other and reduce charging capacity in this kind of setup.

As already mentioned, I'm a fan of each engine having it's own electrical system (starter, alternator, and battery). That way a failure in the battery system doesn't prevent both engines from starting. Also not sharing batteries also eliminates an accidental draining of all batteries. Having a second alternator on one or both engines for charging the house bank, keeps everything simple. You could have paralleling switches to over come a dead battery or simply keep a set of jumper cables on the boat. My boat (single engine) is setup this way with a simple dedicated engine battery, starter, and alternator. The house bank is charged by a second heavy duty 220 amp alternator. There is a paralleling switch as it was there from the previous setup.

Had a really bad experience with a multiple battery charging isolator block when one of the diodes went bad and the voltage shot through the roof, never again.

Ted
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Old 12-22-2015, 10:43 PM   #13
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Threads like this inevitably get very confusing such as this one already has. I would get a copy of Nigel Calder's or Charlie Wing's marine electrical books and study them before jumping into anything.
True enough, but with all due respect, all of these threads ALSO end up with someone saying to get and read Nigel's book... And I have. Many times. However, I still believe it is good practice to ask for opinions based on what has and has not worked on other boats. While you can look at Calder's book as a textbook, and even a guide, there is STILL no substitute for experience.

But thanks for the reply.
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Old 12-22-2015, 10:59 PM   #14
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I'm a fan of each engine having it's own electrical system (starter, alternator, and battery).
That's not a bad way to go. Bank 1 & 2 as just starters and 3 as only a house. Although, I don't think I have the ability to add another alternator to these motors to provide charge to the 3rd bank. So I may have to do a duo charger of some kind to make that work... OR just rely on the genset running the charger as a stand-alone bank. Not bad.
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Old 12-22-2015, 11:11 PM   #15
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The other option would be to charge the house bank with one engine's alternator. Then charge that engine's battery with an electric charger. There are 12 volt battery chargers that are powered by 12 volts DC. So you could power the charger off the house bank. Think of a 10 or 20 amp electric battery charger, only not 120 AC but 12 volts DC.

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Old 12-22-2015, 11:34 PM   #16
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Sterling Power Alternator to Battery Chargers are just the ticket. They trick your stock internally regulated alternator into putting out more current by lowering the voltage that they see and then charge your batteries properly by regulating the increased output current. It is truly magic and it works. You can also connect up to four alternators. The batteries and an alternator is protected by temperature sensors. I have one and it is great!

https://cdn.shopify.com/s/files/1/06...s/A2Bs.pdf?743

and for a US source see here:

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Old 12-23-2015, 08:01 AM   #17
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6.3 turbo Volvo's. 318hp TAM 63L
Quote:
Originally Posted by kulas44 View Post
A single group 31 will easily start that engine. I would have a dedicated pair of 31s for each engine.

Agree, a single G31 for each could well suffice. Think I'd examine the option of a single battery each first, before deciding whether to install two for each engine. Engine manual and starter should inform as to minimum CCAs/MCAs, so you can compare from there.

FWIW, the Odyssey PC-2150 is an AGM example of a G31 that can put out huge cranking amps... if you're thinking at all about AGMs.

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Old 12-23-2015, 08:58 AM   #18
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Hello team!

As my introduction to our new 42’ 2000 Navigator continues, I had a chance to spend some quality time in the bilge to figure out exactly how the factory has wired this wonderful vessel. As was documented in an earlier thread, we have had a total failure of battery #3 and the other two are below 80% of rated... so they are on their last leg too. All of the batteries are currently 8D Ray-O-Vac’s from Batteries Plus (NOT deep-cycles), but will all be replaced. Let me also say that there is quite a bit of space to add multiple batteries and also vertical space. Where the #3 battery sits, there is a deck about 36x12 and where 1 & 2 sit is about 48x12.

Below is the diagram and I will point out a few of the features.














































Real pic of switches (I am sitting between engines looking starboard):


Battery location (aft under cockpit, still sitting between engines looking aft)


It’s a fairly ingenious design. As it sits, each battery can be isolated for any task. Meaning, there is no “starter bank” or “house bank” designation. That frees me up to design the new system as-needed.

Charging is not tied to the battery switching. I think that is a good thing.

One thing I see as a problem is that all the alternators are tied to the starter posts. Even the genset.

Another thing I am curious about is that the two engines starters are tied together. How common this is I can’t answer because this is our first twin-engine boat. The engines are, by my standards, large, however, I am not the expert. I don’t know how much juice is needed to crank them over. Maine Sail (the guy from Compass Marine) consistently says that starting smaller sailboat engines is a breeze with a house bank, however, I don’t know if these big Volvo’s fall into that category. The instruction book makes only a couple of references to batteries. One of which says the electrolyte density, but the other says: Battery capacity for a 12V system……… 2x12V connected in parallel. max. 110Ah (total max. 220Ah), so it’s hard to say one way or another exactly what is “required” to start these gals.

Finally, the battery switches are all the way in the bilge. That is good and bad. The good is that making an error while underway is less likely. The bad is that it brings in the out-of-sight-out-of-mind mentality and opens the door to an error when anchored or access during an emergency. That may change in the future, but for now, I will just note it and move on.

Here is what I am considering. Let’s say, for a moment, that I do indeed, need to have a separate starter bank for these motors. Would it make any sense to make one bank a pair of dual purpose 12V batteries (Group 27 in parallel maybe?) specifically for that task? Part of me says yes, but unless I start switching around the switches whenever I start the motors, I would me mixing the starter bank with the other two banks. In a way, that seems pointless. But that does still leave me room for two banks of four 6V golf cart batteries (if sized from Trojan T-105s, although there is room to go with taller batteries with even more amp hours).

Otherwise, if we determine my motors do NOT need dedicated starters, could I not go 100% golf cart on all three banks? I will eventually want to put in a medium-size inverter, so the way I see it, the more the merrier.

I am not afraid to make some major changes, however, considering that this is a fairly good setup, about the only thing I might need to do other than all new batteries and a few lug changes would be to maybe move the alternator feed wires… but to where, I am not sure. Then, maybe next year, throw in some buss bars and move the switches up to the main salon. It’s not a very far move. Just a foot or so above (through the floor) from where they are in the bilge and into a cabinet below the breaker panel. Still, that would be a fairly big task that I am not really ready to tackle.

Look forward to your opinions.

In my opinion, a great circuit ! Assuming that the switches are of good quality and Amp rating. I would maybeee ? add fusing on each battery circuit...
I just re wired my main DC and I wish I had seen this diagram before. My wiring is close to yours BUT I will definitely keep this diagram if I ever decide to redo what I have done.

Frank B.
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Old 12-23-2015, 09:21 AM   #19
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Agreed, looks like a good simple setup. I'm not a fan of fused starting circuits, some are. Later, if you decide to add an inverter/charger, an AGS with Batt monitoring could be used to start the gen when Batt voltage gets to a preset level on the house bank. Magnum makes a good AGS unit thats plug and play for there inverter panels.I like the house bank to be isolated from the start bank, for obviuos reason. IMO that every engine needs its own solated start batt.
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Old 12-23-2015, 11:51 AM   #20
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My boat came to me wired somewhat like the diagram. However handy it may be to be able to switch out various batteries, connecting the alternators together will ensure that you'll get full output from only one unless you have something like Balmar's smart regulator.

I rewired my entire charging system last spring and was able to double the effective amount of power from the existing alternators. As it turns out there is an article in the latest Soundings which talks about wiring the banks just the way I did it. (Alternator outputs go to the 2 house banks, then through Automatic Charging Relays to each engine start battery)

Ken
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