DC System Discovery Day

[BruceK]

I have no plans, at all, to buy bigger alternators. Heck, if you saw the setup, I doubt I could get a bigger one in there. I am, however, considering a stand-alone battery for the genset that isn't in the charging system for the rest of the boat. I suppose I would have to remember to start it up often enough to keep it charged or keep jumper cables/starter box onboard should I need it.

My genset battery has a dedicated 25W solar panel with a simple regulator and is always charged.

 

[Tom.B]

Here is an option I am considering.

Adding a "dedicated" starter bank using two dual purpose 12v.

Splitting house to two 4xGC2 banks providing 880Ah

Under normal running and in marinas, 1/2/B/O switch in position 1 and on/off set to on. At anchor, 1/2/B/O switch to position 2 and on/off set to on.

Alternators moved to house banks

Genset system isolated to dedicated starter battery charged by a CR relay or Duo Charger.

 

[O C Diver]

Never been a fan of having to charge battery switch positions in routine operations. Also, not clear as to the advantage of splitting the house bank. Why not build the start bank for both motors as you describe with one alternator charging it. Use the other alternator to charge one large house bank. Add a battery switch to combine the two for a battery failure or alternator failure.

Ted

 

[Capt.Bill11]

I think you are making it overly complicated. And I'm not a fan of hooking multiple alternators together without the proper isolation.

 

[FlyWright]

If your charge and load circuits are not already split, I'd do it. Wire your charge straight to the batts. Then you'll never have to move the load switches during normal operation and the ACRs will share the charge as needed.

 

[Tom.B]

I think you are making it overly complicated. And I'm not a fan of hooking multiple alternators together without the proper isolation.

I am trying to keep it as simple as I can with what I have to work with already. I don't want to reinvent the ENTIRE system and spend days and days and lots and lots of money buying and making new wires and connectors. Been there... Done that. This design only requires minor changes. Look at the picture of the switches in my first post. Major reconfigs of the wiring will be a huge PITA.

Besides, this seems to be an improvement. With the switches in the marina/underway setting described above. None of the alternators are tied together. I think.

 

[Tom.B]

Never been a fan of having to charge battery switch positions in routine operations. Also, not clear as to the advantage of splitting the house bank. Why not build the start bank for both motors as you describe with one alternator charging it. Use the other alternator to charge one large house bank. Add a battery switch to combine the two for a battery failure or alternator failure.

Ted

I only see the switches changing when I reach an anchorage. And don't all the rules kind of change then anyway?

As to your build idea, I am not opposed to it, but like I told Bill, I don't want to reinvent the wheel here. I just don't have the time, money, or willingness YET, to undertake it. There are more pressing issues at hand.

Thanks for the reply, sir.

 

[Tom.B]

As to your build idea, I am not opposed to it

I know quoting myself is in bad taste

BUT, I will try to reconfigure it with two starter/dual purpose banks and on big house bank that won't be too much of a pain to do.

Thanks again.

 

[Larry M]

... Also, not clear as to the advantage of splitting the house bank. Why not build the start bank for both motors as you describe with one alternator charging it. Use the other alternator to charge one large house bank. Add a battery switch to combine the two for a battery failure or alternator failure. Ted

We have a starting bank and a house bank. One alternator/voltage regulator for the house bank and one for the starting bank. Nothing to switch unless there is an issue and there hasn't been. I guess what I'm trying to say is one large house bank is simpler than 2 smaller ones and less risk of drawing down a set of batteries in a split house bank.

 

[Tom.B]

one large house bank is simpler than 2 smaller ones and less risk of drawing down a set of batteries in a split house bank.

After giving it some thought, I think I am beginning to agree. However, I need to find a way to reconfigure the system in a simple-ish way.

 

[Capt.Bill11]

Whats the amperage output of the alternators you have now?

 

[Tom.B]

Whats the amperage output of the alternators you have now?

I believe the two main engine alternators are 60A each. Actually, the manual calls them generators.

Here is the next generation diagram. Yes, it will take a little more doing, both in effort and cost, but I think it won't be too bad.

It adds a switch and does away with the 1/2/B/O switch. It's what I did on the last boat... And I suspect, more in line with what people here would recommend.

 

[koliver]

I am sure that what is being proposed here will work.

But, I have trouble justifying the excess no of batteries for starting. Here is what I have:

4x6v Golf cart for the house
1 single 4D Start for 2 x TAMD41 Volvos + 1 x Westerbeke 4kw genset.
1 x combining solenoid, should either the house bank or the start bank die and I need some juice from the live bank.

When I bought this boat in 1994, there were 2 x house banks, 1 was 2x 8D, one was 2x 4D. I reduced demand by changing fridges, added an Inverter/charger (Xantrex 2000W, that charges at 100 amps). All of this is regulated by "smart" 3 stage regulators.
I replaced the 4x6v batteries in the house system after 10 yrs, 2 yrs ago, when they showed slow charging. The 1 x 4D start battery is still providing good service after 12 years, never uses a lot of water, never slow to turn over an engine.

I haven't had to use the combining switch to start, in 21 years.

In my Motorhome, I have a pair of car sized start batteries, wired in parallel. they start the Cummins ISL400, that is beside them, and the Onan 10kw genset that is 40' away, without difficulty. There is a combining solenoid, should the need arise.

There are thousands of Motorhomes set up this way. I know of none that have a dedicated start battery for the genset and another for the main engine.

If yours was mine, I would save the weight and cost of the extra start batteries and get one big enough for the big Volvos, use it serially, on all three engines, and sleep well.

 

[Rossland]

Here is my 2 cents:

1. The generator start battery should not be connected to anything else. That way you will always be able to start the generator (And the the AC battery charger) even if all the other batteries are dead.

2. The two main engine alternators should be connected to a Balmar Centerfielder regulator (or another brand that does the same). Otherwise, one alternator will "fool" the other alternator into thinking that the batteries are fully charged.

3. The start batteries should be connected together, or alternately you could use one start battery of sufficient size.

4. The house batteries should be connected together into one bank. The start batteries should be connected to the house batteries by using a combiner such as a Charles BattCom.

5. The AC battery charger should only be connected to the house batteries. The start batteries will also be kept topped up thru the combiner.

6. And if all else fails, I carry a pair of booster cables, so I can boost anything with anything, even my dingy battery.

Hope this helps. This is basically the system that I have on my boat, and it works well.

 

[Tom.B]

Thanks Ross... I have never heard of the Charles BattCom or the Centerfielder and will look into them.

I have to ask: Why not split the alternators between a house bank and starter bank? You aren't the first person to suggest using an ACR type relay to charge the whole kit-and-kabootle with just one alternator and I am curious what the thought process is that leads to this.

 

[Rossland]

Thanks Ross... I have never heard of the Charles BattCom or the Centerfielder and will look into them.

I have to ask: Why not split the alternators between a house bank and starter bank? You aren't the first person to suggest using an ACR type relay to charge the whole kit-and-kabootle with just one alternator and I am curious what the thought process is that leads to this.

Typically, it takes very little power to start an engine. Yes, there is a very high amperage draw, but it only lasts for a few seconds. Therefore, a large alternator will fully recharge the start batteries in a couple of minutes. However if your boat has not been connected to shore power for a while, the house batteries may be deeply discharged, and may take several hours to fully recharge.

The system that I described will result in both alternators producing the same amount of amps at all times. This means that there is an equal load on both engines, and there will be the combined output of both alternators available to charge the batteries.

A combiner is nothing more than a relay which opens and closes at a set voltage (13.3V in the case of the Charles Industries version) This means that both the start and house batteries are connected together when the batteries are fully charged. Then when the engines are not running and the house loads draw the voltage down to 13.3, the relay opens, and the start batteries are not discharged any further. When the engines are started, the alternators charge the start batteries first, then when the start battery voltage reaches 13.3 the relay closes, and the alternator output is fed into the house batteries. You can accomplish the same thing with a manual switch, but I would forget to turn the switch half the time, which is why I rely on a combiner.

 

[Tom.B]

I like your thinking, but I think that if I went that way, I would connect the alternator (or in the example... the Centerfield) to the house and use a Balmar Duo Charge or Blue Sea ACR (or the Charles thingy) to charge the start batteries. Possibly just semantics, but I am more of a fan of alternators going to house banks instead of starts. But that's just me.

 

[Tom.B]

Like so:

 

[Rossland]

Like so:

That would work well. The only improvement that I would suggest is that the generator should have its own start battery. If your start batteries were to become discharged (say by a failure of the combiner), you would not be able to start the generator either.