Twin alternator option on Beta Marine engine

[scott2640]

I'm currently gathering quotes for our engine on our home built 41' Diesel Duck. It will be built of wood with a 42,000 pound displacement.

Our preferred engine is from Beta Marine. They offer an option of a 2nd 120 amp alternator in addition to the included 65 amp alternator.

I need to preface this with the fact that I know nearly nothing of DC electrical systems so I won't be insulted if you dumb down your explanation.

This boat will be our winter cruising home for my wife and I. We would like to spend significant time "off the grid" away from Marina's. We would also like to have many of the electrical comforts of home while we cruise. These would include Air conditioning in the state room, television, computer, gaming system, cooking equipment, a small midi wood turning lathe along with more traditional demands of navigation equipment, lighting, etc.

Is money better spent on a larger battery bank, genset, solar panels and inverter?

What is the benefit of the 2nd alternator? Would this advance our goal of electrical surplus?

Or is the addition of a 2nd alternator principally for some other use or mission objective that I'm missing?

 

[O C Diver]

It depends.....

If you plan to run air conditioning when at anchor, a generator will be a requirement.

The second alternator with an external 3 stage regulator shines for recharging the banks while underway and can provide up to 3KW of AC power while underway. If you plan to spend a fair amount of time off the grid a large battery bank will be important whether you use solar, wind, engine alternator or generator to charge it.

Imo, the 120 amp 2nd alternator is a little on the small side (mine is 220 amps). To some degree the size of the second alternator will depend on the size of the battery bank, as the bank can only handle so many incoming amps based on it's size.

Determining your needs and then the size of the bank, will ultimately lead you to how big your recharging system should be.

Ted

 

[Lepke]

If you want off grid AC, house appliances, etc., you're going to need a generator, good inverter, bigger fuel tanks and lots of batteries. I don't think you can do what you want to do in 41 feet. I never could.
Building a wood boat is thousands of man hours to completion. I know, I've done it alone and with crews. I'm a shipwright and worked on and built large wood boats and small ships. Many people building boats from scratch think it's cheaper or easier to pay as you build. Most never finish. Some that do are too old to do what they started out to do. That is cruising.

Your money and time would be better spent buying an older wood boat and putting less time and less money there. You'll have engine(s), alternators and other things you can improve on. And actually be able to use the boat. As to home store wood, when I rarely buy home store wood, for 2x4s, I buy a 16' 2x12 and am lucky to get 2 - 8' 2x4s when I trim it down. And I live in a timber county. Your wood is full of knots. Rot likes to travel around knots. Along with being less strong.

I do what you want, but in 83 feet. I have 3 - 48v banks for the inverter and 2 - 12v banks for each main + a 12v bank for misc. house. I can anchor for about 3 days without running a generator, depending on how many people are aboard. No city people, maybe 5 days. But I rarely run AC. About 3 days this year.

 

[FF]

"I need to preface this with the fact that I know nearly nothing of DC electrical systems so I won't be insulted if you dumb down your explanation."

If you make a list of the power used , and hours operating , you will have a far idea of the daily power requirement.

Depending on what you choose the power needs can be cut , but better more efficient gear is more expensive.

Refrigeration is one example , a Sun Frost reefer is great , and can be purchased , rather than attempting to create a more efficient built in unit.

In some cases a small and larger set of noisemakers work better than a ton of batteries , multiple charge sources and the effort involved in maint .


I suggest you get this free catalog as it has many ideas on living well with minimum energy .


http://www.backwoodssolar.com/catalog-request

 

[Larry M]

We have two alternators on our single FL135, one for the engine start bank and one for the house bank. Both have their own 3 stage alternators and are independent systems with no internconecting switches. Voltage regulators and alternators are indentical and are interchangeable plus I carry one spare for each. In over 20,000 miles I’ve never had a dead bank or had to jump one to the other. It’s a simple system.

 

[dhays]

Determining your needs and then the size of the bank, will ultimately lead you to how big your recharging system should be.

I agree with Ted. Since you are starting from scratch, you should follow the above sequence.

Having said that, if you need to get a quote, I’d have them quote it with the larger alternator. It won’t be too big!

So figure out what your electrical needs will be. You listed a LOT of potential AC appliances and devices. Take the time now to figure out how much power those devices use at your dirt home. If you are powering them on a good inverter, they will take roughly an additional 15% power from a battery bank.

If you want air-con, then as others have said, you will need a genset.

I don’t know DC systems either, so I can’t offer any practical advice other than what has already been said. However, Ted’s advice above is a good place to start.

 

[DavidM]

As noted above, the only way to run an air conditioner at anchor is to run a generator to power it. It is too much load for a battery/inverter system.


You need to think through how you will cruise to determine if it is valuable to have a second alternator on the propulsion engine. If you just stop for a day or two at anchor and then continue on for several hours to the next anchorage, then the charging capability of the second alternator could be useful. But as noted above, you need a big enough battery bank, probably 800+ amp hours of capacity, to use the full capability of the second alternator. Also Beta offers a Balmar alternator instead of the OEM alternator which will increase your charging output to 100+ amps.


If you hang out on the hook for 3+ days at a time, then you need to have the ability to recharge your batteries without running the propulsion engine as it is not good for it to run lightly load as would be required for battery recharging. So that means a generator driving a shore power charger (as in an inveter/charger combo) probably combined with solar panels to top off the batteries during daylight. Or if your DC consumption is moderate, maybe solar panels can supply it all.



So analyze how you plan to cruise before jumping in to twin alternators.


David

 

[FF]

"So analyze how you plan to cruise before jumping in to twin alternators."

Twin alts are a delight , as are isolated batt systems .

The alt to the start batt can be a stock one wire imbecile , the alt to the house is probably best a large frame with twin belts and of course a smart V regulator.

Some items like TV can be 12V (from the RV folks Jensen) and not need an inverter and its losses.

Hot water can be done the old way , a black tank or bladder on the cabin top , drains with gravity , filled with a power or hand pump.

Air cond is always nice , but in many locations like the Carib it is not necessary.

The breeze is usually 080deg to 120deg at 10k to 15K so sun covers and good sized hatches do a great job.

With buckets the deck can be sloshed to get rid of any daily captured heat , and the vessel brought down to near water temperature , cool enough to sleep.

 

[Aquabelle]

Balmar makes a single regulator that can manage two alts on a single engine, directing all charge to the House bank. That's what you want to do given the objectives you've outlined as this will minimize recharge time. The Starting battery can be maintained with an echo charger or Balmar digital duo charger. You cannot hurt the batteries by oversizing the alternators as a quality regulator and the batteries themselves will look after that. In fact oversizing the alternators will mean they run cooler and last longer.

 

[DavidM]

You cannot hurt the batteries by oversizing the alternators as a quality regulator and the batteries themselves will look after that. In fact oversizing the alternators will mean they run cooler and last longer.

Well, yes and no. A 200 amp alternator charging a 100 AH house bank will soon destroy the battery if the "quality regulator" isn't set properly. Conventional wisdom is that flooded cell batteries should only be charged at 25% of their AH rating, AGMs maybe a little more.

You could set the maximum charging rate at 25 amps with a "quality regulator" and protect the battery. Not sure if Balmar's regulators do that though. Balmar's battery temp sensor drops the amps in half when it senses hot temps. That may be ok for 400 AH bank and a 200 A alternator.

David

 

[caltexflanc]

Get yourself a copy of Nigel Calder's "Boat Owners Mechanical and Electrical Manual" and then turn off the internet and read the first several chapters (and eventually all of them except the sailboat specific stuff). Then you will be well educated and can come back here if need be to gather the relevant (and know what's relevant) experience of others. After you read that book (but only after), you could take a look at, ZRD's weird but wonderful website or give them a call for some alternatives. They are extremely expert on DC systems.

 

[GoneFarrell]

Caltex's advice on Nigel's book is spot-on. It is a straight-forward bible for the issues and questions you seek to answer as an owner/operator/fixer, whether you buy/rebuild used or build new.

My boat runs a 24 VDC alternator for charging the starting bank and a 12 VDC alternator for the house bank. They are separate electrical systems/separate chargers too. If the 24 volt bank ever went dead I can move a couple cables and jump the starter from the house bank, or recharge from a 2KW portable genny I keep topside. Anything bigger is too heavy to move around by hand.

Ask yourself if you will have thrusters and an electric anchor winch too, those are the biggest intermittent DC loads other than starting the engine. Running those loads at 24 volts will keep the long copper wires smaller and cost less.

 

[CMS]

What is the benefit of the 2nd alternator? Would this advance our goal of electrical surplus?

Or is the addition of a 2nd alternator principally for some other use or mission objective that I'm missing?

In order to answer this question we'd really need a lot more information. Dual alternator systems are very, very useful and provide redundancy over single alt installations. If you have a large bank and high demands it will be best to make the second alternator a large frame unit (not a small frame), 160A to 200A, such as a school bus type, if possible. Stan can create a mount for any alternator you choose and he will even allow you to ship him your alternator of choosing. It is far less costly to have Stanley do this now rather than doing it later...




-Daily Ah consumption?
-Battery type AGM, GEL, Flooded?
-True deep cycle batteries (Golf car better)?

-Battery bank Ah size
-Other charge sources?
-Loads fridge, freezer, watermaker, electric cook top or gas etc. etc...