Second alternator or DC to DC charger

[David Griffiths]

Complexity or simplicity?
47' live aboard motorsailer. 4 x 175watt solar panels, no genset, AGM house batteries, sealed lead acid start.
OEM 120 amp alternator with internal standard regulator.
Question: Leave the OEM alternator to look after the start battery and thruster battery bank and add a second 120 amp alternator with external reg (Balmar?) to look after loads applied to the house battery system OR continue to use a single alternator and add a DC to DC battery charger to maintain the house battery system?
Nigel Calder, my go to reference advocates "by far the best arrangement is to add a second high-output alternator to look after the house battery system" BUT this book was written in 1996.
Is the mechanical whiring/complexity of a second alternator now superseded by the electronic wizardry of the new DC to DC charging systems?
Redundancy: Carry a second alternator? Jumper leads (or parallel switch connection) to join the house system to the start battery system.

 

[mvweebles]

Similar setup with 800w solar though with a larger LiFePO4 house bank. All charging goes to house bank with DC-DC to engine snd generator start (both AGM). I do have a pair of high output Balmar alternators though they are run through a single dual regulator for a total of 200a @12v charge potential. You'll have to decide whether you need that much charging potential.

Good luck

Peter

 

[David Griffiths]

My boat: Single JOHN DEERE 6.8
The question of charging potential is more a question about system balance, ie: need for power to run appliances being equaled by battery charging ability.
My understanding is to not regard the alternators as "battery chargers" they are to handle loads imposed on the system while the engine is running.
Battery charging is BEST accomplished by DC to DC chargers and/or solar panels. (I'm sure this will start a fight....)
I guess my question is really mechanical, spinning things, heat generation vs electronic wizardry. Which is more reliable? Which is better for battery health? Which is more user friendly/servicable in the long run?

 

[mvweebles]

I don't agree with the premise that alternators are primarily used for powering load while underway. Certainly true in a motor vehicle. Not true on a cruising boat or RV. Alternators have a strong use-case as a charging source for battery replenishment. Besides, your boats DC panel is likely cabled to your house bank so you're effectively running off that when underway. This puts starter battery as intermediary. I know this was conventional wisdom, but that has evolved with large house banks and large alternators and solar.

DC-DC chargers are limited to around 40a (12v). Power transferred is adjustable and fairly clean at any rpm. Main benefit to DC-DC is as Rosetta Stone between dissimilar chemistry batteries. If your house bank is small, 40a charging might be okay, but I'd still rather have 120a alternator charging the house bank, then charge the start battery. If no major chemistry difference, an ACR would allow full charging current between the banks.

I think you're hung up on mechanical vs electronic. You may want to focus on system design compared to your overall usage.

There are a few really sharp people on TF who will hopefully respond. As a tip, a sketch really helps avoid any misunderstanding.

Good luck

Peter

Edit - decent related article by Steve D on sizing alternator and use of dual alternators.
https://stevedmarineconsulting.com/the-relationship-between-battery-bank-size-and-charge-capability/

 

[DavidM]

I don't think a DC to DC charger is a good addition to a standard, internally regulated alternator. The DC2DC will put more continuous load on the alternator than it can handle and it may ultimately burn up.

A simpler solution to a second alternator is to install a bigger, high output alternator in place of the existing one with an external regulator such as made by Balmar. Be sure to get the temperature probe to reduce current when it gets too hot.

David

 

[mvweebles]

I don't think a DC to DC charger is a good addition to a standard, internally regulated alternator. The DC2DC will put more continuous load on the alternator than it can handle and it may ultimately burn up.

A simpler solution to a second alternator is to install a bigger, high output alternator in place of the existing one with an external regulator such as made by Balmar. Be sure to get the temperature probe to reduce current when it gets too hot.

David

OP - David here is one of the most knowledgeable TF people I was hoping would respond. You may do well with a quick sketch of what you have and ask an open-ended question about what is the best bang-for-buck upgrade might be.

David - couple general questions: what's your thinking on running single alternator to start-battery vs large house bank? For AGM + Sealed Lead Acid, can a simple ACR combine them, or is the chemistry different enough that a DC-DC is needed?

Peter

 

[O C Diver]

If you have a single engine boat (as I do), dual alternators are absolutely the way to go.

First, there is the value of redundancy. Cruise long enough, and sooner or later the alternator will fail (brushes, regulator). With a paralleling switch you now have the capacity to provide power to all systems.

Secondly, most engine alternators aren't designed for continuous high output amps. Choosing a second high output alternator allows you to have and utilize one specifically designed for that purpose.

Third, with 2 alternators, you can configure your 12 VDC in an optimal manner. For me, that means nothing on the start battery except the engine and related electrical. Simply, when the engine key is turned off, nothing draws from the start battery. The large second alternator charges the house bank. In this scenario, draining the house batteries has no impact on starting the engine.

Having a paralleling switch as previously mentioned, allows me to start the engine from the house bank should the engine battery fail (which it has). It also allowed me to maintain the house batteries when the Sterling external regulator (POS) failed. Balmar regulator is a much better product.

My choice for the second alternator was a large frame commercial grade 220 amp Leece Neville. Have been extremely happy with it. On my TF user page, there is a photo gallery with pictures of the installation if you're interested.

Ted

 

[rslifkin]

Personally, I run my alternators to the start batteries, then ACRs to the house bank. The ACRs are ignition interlocked so they'll only engage when the engines are running and stay out of the picture for charging on shore, generator, or solar power. Start and house batteries are all AGM on my boat. They're different brands and do spec different charging voltages, although the alternator output falls a bit above float voltage (but below absorb) for both, so while it's not ideal for fast charging, it does get them charged without cooking the batteries. The house and start batteries do have separate shore charging systems, etc. to accommodate the voltage differences.

With my setup it's easy enough to confirm the alternators are working as well. When each engine is started, you should see the volt meter on the instrument panel for that engine come up to indicate good alternator output, then after a couple seconds it'll flick downward a bit as the ACR engages for that side. The ACRs are connected to the engine side of the battery switches so if a start battery fails and I switch both engines to 1 start battery I still get both alternators connected to the house bank.

I've also followed the same method as OC Diver where nothing at all draws from the start batteries that doesn't run through either one of the engine ignition keys or the generator start switch.

If I switch to LiFePO4 at some point, I'll have to decide whether to add a second externally regulated alternator to each engine (and run those directly to the house bank) or replace the ACRs with DC-DC chargers.

In my case, my engines require power to run, so I consider ensuring that the starter batteries are topped off to be more important than charging the house bank (as I have other charging sources beyond the alternators if needed). I'd much rather let the alternators bring up voltage on the start batteries, then start charging the house bank vs spending a while charging the house bank while the starter batteries slowly draw down.

As far as cooking an internally regulated alternator, I agree, it's definitely a concern. In my case, the alternators are low enough output relative to their physical size, etc. so they don't seem to have a heating problem even when dumping full power into the house bank for hours on end. A higher output unit of similar size would likely have issues if the regulator doesn't de-rate on temperature, however.

 

[mvweebles]

If you have a single engine boat (as I do), dual alternators are absolutely the way to go.

First, there is the value of redundancy. Cruise long enough, and sooner or later the alternator will fail (brushes, regulator). With a paralleling switch you now have the capacity to provide power to all systems.

Secondly, most engine alternators aren't designed for continuous high output amps. Choosing a second high output alternator allows you to have and utilize one specifically designed for that purpose.

Third, with 2 alternators, you can configure your 12 VDC in an optimal manner. For me, that means nothing on the start battery except the engine and related electrical. Simply, when the engine key is turned off, nothing draws from the start battery. The large second alternator charges the house bank. In this scenario, draining the house batteries has no impact on starting the engine.

Having a paralleling switch as previously mentioned, allows me to start the engine from the house bank should the engine battery fail (which it has). It also allowed me to maintain the house batteries when the Sterling external regulator (POS) failed. Balmar regulator is a much better product.

My choice for the second alternator was a large frame commercial grade 220 amp Leece Neville. Have been extremely happy with it. On my TF user page, there is a photo gallery with pictures of the installation if you're interested.

Ted

At the suggestion of TwistedTree (BLOG post HERE), I went with two alternators but a single Balmar 612 regulator to gang-together the two outputs into a single large output. Redundancy is automatic if one fails. Now, I really do not have room for a large-frame alternator or that would have been my preference. I also happened to have a spare 70A Balmar laying around so coupled with a 150A. I could have run the 150A to my house, the 70A to my start, but felt it better to have full 220A potential to my house bank.

NOTE - the Balmar 612-dual only works with dual alternators on the same engine, not one alternator each on two engines.

Peter

 

[DavidM]

David - couple general questions: what's your thinking on running single alternator to start-battery vs large house bank? For AGM + Sealed Lead Acid, can a simple ACR combine them, or is the chemistry different enough that a DC-DC is needed?

Peter

I have never used a mixed AGM/FLA combination, but I think that the charging parameters of these are close enough that using a single ACR to combine them would be fine.

Re another post: Although it is more complex to wire, I prefer that the engine alternators charge the house batteries and an ACR or Combiner ties in the start battery when the voltages are right.

Why? Well the house batteries probably get 95% of the current from the alternators so it makes some sense for them to be the primary connection to the alternators.

David

 

[DDW]

Whether one or two alternators, if living about and depending on the batteries, you definitely want external regulation. Internal alternator regulators just aren't designed for this type of use. There are many brand name alternators that can be used (Delco, Leece, etc) and converted to external regulation for a small fraction of the price of a Balmar. The best external regulator today is the Wakespeed WS500, but a Balmar is a bit cheaper and can work OK.

 

[David Griffiths]

Thankyou all for your valuable contributions.
It would appear that there is not one absolutely ideal scenario.
Space. Cost. Complexity. Availability of parts and knowledgeable assistance. Owner understanding and ideology all have an input into the decision.

 

[Jeff F]

I agree that an external regulator is a good first step. When properly set up it will protect your alternator against overheating, and should take good care of a single chemistry bank.

I completely overhauled my charging system a year ago, with a single 170 amp alternator charging the FLA house bank through a Balmar regulator. Also have 700w solar charging the house bank.

Three other battery banks - one start, one bow thruster/windlass, and one 24v stern thruster - each have their own 30 amp DC-DC charger drawing from the house battery with voltage limits set to turn on when the house bank is being charged.

After a year of full time traveling with this arrangement I can't think of anything I'd do differently. I carry the OEM alternator as a spare for field repairs.





Sent from my moto g play (2021) using Trawler Forum mobile app

 

[twistedtree]

Lots of good advice so far, and I think you figured out the most important thing which is that there are lots of right answers, not just one or two.


I would start with two objectives.


1) Try to best match the charger size with the load size. Generally a house bank and house loads will be much greater than a start bank. This is both in terms on constant load, as well as recharging demands. This means you usually want to apply the biggest alternator and/or charger to the house bank, and the smaller alternator or charger to the start bank.


2) Consider what happens when something breaks. If you cruising allows you to limp home, or get a tow, then you don't need to worry too much about redundancy etc. But if you want more autonomy, then it's important. So ask yourself what you would do if either alternator failed, or either charger failed, or a combiner failed? Does your system provide an alternator way to maintain power to the engine(s)? Does your system provide a way to maintain house power, including navigation electronics?


I think those are the key things to consider. From there it's a matter of what your existing system looks like, and what's the most effective way to evolve it to what you want. The actual solution you pick will likely be heavily influenced by how your boat is set up today.

 

[David Griffiths]

Thankyou all.
This relatively short sub forum has very quickly pulled together many options (with no angst or aggro).
The alternatives suggested seem to have covered all the major options available.
In our world here is Aus at the moment, parts availability is a key issue. Skilled labour in the marine elec industry also seems to be in short supply.
My boat is 20 years old (and perhaps along with Nigel Calders book) there is a need for update and improvement across all systems.
At age 60, I'm looking for straightforward without the need for a "tech head" with specialised software to make adjustments to any of my systems.

 

[David Griffiths]

in addition:
I don't like wasting peoples time and effort when with a bit of self help a question could have been answered by looking around this (or other) forums or picking up one of the many marine books.
That was why I did'nt ask an open question.
I think that style of question is disrespectful of the available brain power on this forum.
My "2 bob" worth about courtesy and responsible forum behaviour....

 

[twistedtree]

There are a number of people here from Aus who might be able to help re suppliers and tradesmen.


And Welcome! You are off to a good start.

 

[Simi 60]

Question: Leave the OEM alternator to look after the start battery and thruster battery bank and add a second 120 amp alternator with external reg (Balmar?) to look after loads applied to the house battery system.

This gets us into this territory imho

Sure, it has its downsides (fixed rpm) but seeing as you are in Oz the upside is $$ and output.
A Balmar will set you back $3000 + plus install
A 10kva Genset head is around $400

An electric clutch could be a good way to interconnect and engage - disengage load. (I have not fully investigated this yet)

Post #30

A 10kva Mecc Alte brand made in Italy and set up to be belt driven.
With outlet fitted, $395 + gst

Reckons he's sold plenty over the years, never had a return
10kva 50hz 240v is only 245mm wide and 460mm long

https://www.trawlerforum.com/forums/s4/load-dump-lifepo4-generator-battery-charger-62840.html

And welcome

 

[Neil Ramsey]

I bought a 200 amp brushless alternator from an oilfield industrial supplier for $320 CAD. A small machine shop made serpentine belt adaptors for a couple of hundred more. A Wakespeed external regulator, WS100 or, better yet, the WS500 will control the charging and protect the alternator. You should be able to find similar savings down under if you hunt around.
Simple and dependable.

 

[David Griffiths]

Thankyou Neil
What was your thought process in selecting a second alternator over the DC to DC charger path? ie a mechanical solution over the current crop of "clever charging devices"
Many will say when asked this question "redundancy." I suspect a second alternator could be on board as a spare, and installed reasonably quickly if the primary one fails.
Has anyone had an alternator fail, and cause an immediate shutdown of the engine?

 

[Simi 60]

Wakefield ws500 is $1000+ in Oz
Your $300 200amp brushless alt is a unicorn here
Been on the hunt for one for 3 years myself, closest I got was around $1500.
But hey, if you can find some let me know, I'll buy a few.

 

[Ken E.]

Following this....I have a Renogy dc/dc 50 amp charger in my truck/camper setup and I'm very happy with it in that application. As mentioned, it seamlessly connects LA batteries with lithium and also controls the charging output of the solar panels, sending it to either the house or start batteries as needed. For boats though, it sounds like there are better solutions based on the comments above.

 

[Neil Ramsey]

Wakefield ws500 is $1000+ in Oz
Your $300 200amp brushless alt is a unicorn here
Been on the hunt for one for 3 years myself, closest I got was around $1500.
But hey, if you can find some let me know, I'll buy a few.

Here you go:

http://www.all-tek.ca/index.html

I am using the CH-12200-SS. It is a hair larger than the original but, with a little trimming on the mount, it fits just fine. I've had it 3 years and it pumps out 185 amps long enough to bring 4 Firefly's up to tapering from 40% charge without overheating. The WS-100 doesn't start charging for long enough for the engine to settle down and ramps up to whatever full power you want.

 

[Neil Ramsey]

Thankyou Neil
What was your thought process in selecting a second alternator over the DC to DC charger path? ie a mechanical solution over the current crop of "clever charging devices"
Many will say when asked this question "redundancy." I suspect a second alternator could be on board as a spare, and installed reasonably quickly if the primary one fails.
Has anyone had an alternator fail, and cause an immediate shutdown of the engine?

No, I replaced the old 55 amp original. (Westerbeke W46 in a blow boat)

 

[Simi 60]

Here you go:

Yeah but it's not in Australia.
And it's small frame

Just realised the OP made no mention of big bank or 24v so that could be the difference
Large frame 24v with J180 mount alts are silly money here

 

[Neil Ramsey]

Probably worth an enquiry. I bought an Excel anchor from Australia and the shipping isn't that bad.

 

[Simi 60]

Probably worth an enquiry. I bought an Excel anchor from Australia and the shipping isn't that bad.

85 amp is the biggest they list in J180 24v


http://www.all-tek.ca/marine-brushless.html

Freight on that sort of weight is about $300
And then, because it's over $1000 we get hit with import charges and GST on any purchase now, so probably + 15% extra calculated on purchase and fright combined.

All adds up

Even on Alibaba/AliExpress it'll be around $1300 delivered for a yum cha 24v 200amp J180 mount alt. (Just checked again)
Plus the Wakespeed for $1000.
Buys a lot of diesel for our Genset (-;

 

[Rufus]

Has anyone found a detailed "how to" guide for converting an internally regulated Delco to an externally regulated configuration? The 130Amp Ample Power externally regulated alternator on our boat died last year and I found a decent 120 amp Delco17SI in my pile of car parts. At the moment I have a 55A internally regulated Delco charging the 660A golfcart house bank.... (the tachs run off the alternator)

Alternatively, it is possible to just leave the internal regulator in place and run the 17SI through the external regulator?

Or...can I easily tie in a temperature signal to the 17SI (with internal regulator)? Where do I purchase a temperature sensor?

 

[Jeff F]

Thankyou Neil
What was your thought process in selecting a second alternator over the DC to DC charger path? ie a mechanical solution over the current crop of "clever charging devices"
Many will say when asked this question "redundancy." I suspect a second alternator could be on board as a spare, and installed reasonably quickly if the primary one fails.
Has anyone had an alternator fail, and cause an immediate shutdown of the engine?

I didn't realize this was your first post. Welcome, and feel free to share pics!

I don't think any practical solution avoids the "clever charging device." You're going to be using one in any case, either a smart charger or a smart regulator. That's a good thing in my books. I suspect that those fearful of bulk charging from the alternator are basing it on experiences with crudely regulated OEM units.



Sent from my moto g play (2021) using Trawler Forum mobile app

 

[Simi 60]

I don't think any practical solution avoids the "clever charging device." You're going to be using one in any case, either a smart charger or a smart regulator. That's a good thing in my books.

True, but the inverter charger can be the smart charging device if using a relatively inexpensive gen head as mentioned earlier. (Most boats already have a smart charger)
There are other members on this forum and cruisers forum that have been using this method succesfully for years.

I suspect that those fearful of bulk charging from the alternator are basing it on experiences with crudely regulated OEM units.

I'm not fearful of bulk charging from an alt
But I see no reason to spend bulk coin to do it when it seems there are other far more affordably ways of achieving same