Dual Alternators on Single Engine

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I run two 50 amp alts on the old 453 DD with amp meters, and volt meters. I also run two 40 amp chargers.


Isolated. No combiner.
Regulator on alts set to 15 V to compensate for isolator drop.
On / off switch for each bank.
Fuse protected close to the battery except for the start.


Start battery dedicated. 8 D
Fridge banks x 2 dedicated 4 x 6 v
House bank x 1 dedicated. 2 x 6 v
Spare x 1 dedicated. 1 x 12 v ( portable )
Two blank


Jumper cables.


Simple.


The fridge is the power hog at anchor, wish I could mount a propane fridge on board.
 
I run two alternators. One is 180A for the house bank, and the other is 85A for the start bank. Both are controlled by Balmar smart regulators.

At least one of the guys who has my boat's twin has dual 180A alternators, both charging the house bank. Then he uses a DC/DC charger to indirectly charge the start bank. At some point I will likely do something similar with my 85A alternator. Under normal conditions the start bank gets charged back up quickly and the 85A alternator is doing nothing. I'd rather split the load between the two alternators with each running at the same % of it's rated output. Obviously the bigger one would always be delivering more of the current, but that's what it's supposed to do.

The DC to DC chargers are made exactly for this, and I believe only turn on when the house bank is at a high enough voltage to be receiving a charge itself. So you are never charging by actually drawing power out of the house battery - just diverting charge from the alternator. I think the Balmar Duo is an example of such a device, but I might not be remembering the name correctly. Echo Charger is the other name I have heard. Anyway, I've got lots of other things higher on my project list for now, but some day I'll get to it.
 
Simple is good! We run 2-110 amp alternators off of one engine with 2 external, 3 stage voltage regulators. One alternator is for the house bank and one is for the start circuit/engine gauges only. No interconnecting switches.

We do carry a spare alternator, regulator and jumper cables. Have never needed the jumper cables in 16000 plus miles. KISS :)
 

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I think it's possible...
 

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And looks neat...
 

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Murray- Tell us what engine you have. Bigger engines have room to mount one big alt, and that is the way to go if possible.

I have seen a variety of second alt installs where the mount engineering was poor. Caused lots of trouble. Lots of vibration in the front of a diesel and it likes to break things!! Last one I saw like that was yesterday. Adding structure, mass, rotational inertia and belt side loading up there is not a trivial task.
 
Thanks Ski, and all,

Yanmar 100hp 4JH2-UTE squeezed in by the PO where a 65hp used to reside. Very little wiggle room at the forward end...will measure tomorrow, but it was mere inches. Second one would have to be mounted in the same orientation as original, so rotation and fan would have to be considered.

Will post photo's tomorrow.
 
Those pictures I posted are not just frivolity, they suggest another way of attaching alternators without just hanging them off any old tab and hoping the belts line up. Start with what you require for power, then get the correct alternator(s) and build a proper structure to support them. Remember how belt loads can cause bearing failure then figure out how to drive them. Serpentine are the preferred choice.
 
Greetings,
Mr. LM. If that's a Lehman 120, how did you configure the belts so your coolant hose doesn't pass through the middle? and is that a 3 sheave pulley on the crank? Is there a kit to change that (hose routing)? I think that would be a positive modification in my case.
 
RTF. I have a double groove pulley that is a bolt on to my Lehman. It was part of the install kit for the Dickson hydraulic stern thruster. So those pulleys are available.
I'm also interested in the hose re routing
 
Sorry RT, but the engine's the Dover, FL SP135 not the 120. No mods were made other than adding the other alternator/bracket. The main pulley was on the boat when we bought her.
 
Ditto as above: 2 alternators, 45A Delco for start battery internal regulator, 120A Delco for house bank also internal regulator. No interconnection, jumper cables (never needed). When I cruise I move almost every day so fancy regulators not needed for recharging quickly. My electrical loads are very small due to small, super insulated, refrigerator. & LED anchor & cabin lights.
 
When doing the re-power on my trawler, setting it up with dual alternators like my charter boat was an obvious choice. First, if you are going to go to the effort of setting up dual alternators, don't just add one that's lying around or necessarily the same one as your stock engine alternators. Most stock alternators won't put out their rated amperage for very long. When they heat up, the output is reduced. On my charter boat I needed 120 amps out of the second alternator to run an AC unit. Originally I added a second 150 amp Delco alternator. When the unit got hot, it was barely able to maintain 110 amp output. Ended up switching it out to a 220 amp Leece Neville alternator and haven't had a problem since. The Leece Neville is a large frame truck alternator that is designed for continuous high output applications such as fire trucks and emergency equipment. The alternator is substantially larger and weighs maybe twice what the Delco weighs. For my trawler I decided to use the same alternator but added a 3 stage Sterling regulator as this alternator was more for charging the 900 amp battery back. On my trawler, the primary alternator is only for charging the engine battery as nothing else normally will run off it. All other loads run off the second alternator and the house battery bank. There is a battery switch that will tie the 2 banks together in the event of an alternator failure. The second alternator is mounted on a custom built front motor mount. Had to build motor mounts anyway, so this was a logical mounting choice. Because the second alternator has a quite large capacity, I decided to add a second pulley to the crank and have the second alternator driven by it's own 8 groove serpentine belt. Below are pics of the custom adapter between the 2 pulleys, the mounting, and belt tensioning rod (1/2" Stainless all thread). All brackets and hardware except for the pulley adapter are stainless steel.

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If you think you need more than 220 amps, Leece Neville make this in sizes to over 500 amps. The mounting and diameter are the same, but the body gets longer and the price goes over $1K.

Ted
 
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O C Diver said:
When doing the re-power on my trawler, setting it up with dual alternators like my charter boat was an obvious choice. First, if you are going to go to the effort of setting up dual alternators, don't just add one that's lying around or necessarily the same one as your stock engine alternators. Most stock alternators won't put out their rated amperage for very long. When they heat up, the output is reduced. On my charter boat I needed 120 amps out of the second alternator to run an AC unit. Originally I added a second 150 amp Delco alternator. When the unit got hot, it was barely able to maintain 110 amp output. Ended up switching it out to a 220 amp Leece Neville alternator and haven't had a problem since. The Leece Neville is a large frame truck alternator that is designed for continuous high output applications such as fire trucks and emergency equipment. The alternator is substantially larger and weighs maybe twice what the Delco weighs. For my trawler I decided to use the same alternator but added a 3 stage Sterling regulator as this alternator was more for charging the 900 amp battery back. On my trawler, the primary alternator is only for charging the engine battery as nothing else normally will run off it. All other loads run off the second alternator and the house battery bank. There is a battery switch that will tie the 2 banks together in the event of an alternator failure. The second alternator is mounted on a custom built front motor mount. Had to build motor mounts anyway, so this was a logical mounting choice. Because the second alternator has a quite large capacity, I decided to add a second pulley to the crank and have the second alternator driven by it's own 8 groove serpentine belt. Below are pics of the custom adapter between the 2 pulleys, the mounting, and belt tensioning rod (1/2" Stainless all thread). All brackets and hardware except for the pulley adapter are stainless steel.

View attachment 36548

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If you think you need more than 220 amps, Leece Neville make this in sizes to over 500 amps. The mounting and diameter are the same, but the body gets longer and the price goes over $1K.

Ted
Click to expand...

Nice tidy install, I like it.
 
DCBD said:
Nice tidy install, I like it.
Click to expand...

Dang purdy :thumb:

Took an eyeball measurement today and it looks like there's a little over 3 inches from the cooling 'fresh water' pump to the forward bulkhead. I don't have any experience except for our own boat...in the scheme of things would that be considered "somewhat normal", "tight", or "insanely tight"?

Forgot to mention this - the house bank is four 6 volt Exide Xtra GC-135C golf cart batteries in series parallel for 450 amp hours, and the starting battery is an Exide Commercial 4D starting battery.
 
I'm keeping it simple with one on the only engine. Still, I can see the advantage of having one for each engine. Wouldn't want to have the one engine with an alternator to fail if there were multiple engines, and would want equal loads on the engines.


img_300064_0_25004085531e2d7ccd8683f0863e4037.jpg
 
MurrayM said:
Dang purdy :thumb:

Took an eyeball measurement today and it looks like there's a little over 3 inches from the cooling 'fresh water' pump to the forward bulkhead. I don't have any experience except for our own boat...in the scheme of things would that be considered "somewhat normal", "tight", or "insanely tight"?

Forgot to mention this - the house bank is four 6 volt Exide Xtra GC-135C golf cart batteries in series parallel for 450 amp hours, and the starting battery is an Exide Commercial 4D starting battery.
Click to expand...

That's pretty tight. Adding a second pulley will be challenging. With a 450 amp bank you probably don't want to be dumping more than 70 amps in during charging. So a smaller second alternator may be a possibility driven off the existing belt configuration. Might want to ask the engine manufacturer if that's possible as far as belt load.

Pic is worth 1K words if you want to go further.

Ted

Ted
 
A second alternator is one way to go, but I think you have enough charging power with your current alternator. If it has an internal regulator, you could definitely improve on that.


On my last boat after spending much time and money I finally got my alternator retrofitted to use an external Balmar 3 stage regulator and the difference was huge. I had exactly what you have for a house bank and a 90 amp single wire alternator that took a long time to make any real noticeable difference to my batteries.


I don't know what you have available where you are for auto electric but in Victoria we have a couple of very competent shops, one also does a lot of marine work as well. They bypassed or removed the internal regulator and set it up to use the external regulator for under $200 and that included a complete servicing of the alternator. Then I installed the Balmar 3 stage regulator and never looked at it again.


Even on my current boat I have 4 x 8D AGMs for house power with a Leece Neville 105 amp externally regulated alternator and it works just fine. If you can't get your current alternator set up to run an external regulator you have a couple of options available such as something like what I have or Balmar makes a small case 150 amp alternator that has an internal 3 stage regulator. Or 2 alternators. I've been told that more than 90 amps you should consider a dual belt set up so make sure you can do that if you decide to go bigger.


If your engine is fitted with metric bolts other problems can be encountered if you decide to change to a North American made alternator.
 
Thanks for the advice :)

In case somebody doesn't know our situation, here's the condensed version: We're photographers so will not want to leave an anchorage for many days (weeks) if we find a great spot. When we do leave, the next 'great spot' may only be an hour away. Fast charging times are the goal, without a generator if at all possible. PO put in an additional 40 gallon fuel tank, so we have 140 gallons diesel tankage...even so, fueling stations are scarce around here. Looking at solar, wind, and maybe even fuel cells for topping up batteries when conditions allow.

I have read that when considering a larger alternator, one could go as high as 30% of the house battery banks amp hour capacity...is that right? If that's the case...couldn't I go as high as 135?

Looks like this might squeak in there; PK-4JH2-UTE Yanmar Marine 4JH2-UTE Serpentine Pulley Kit

There's a remote oil filter in the way of a second alternator (if I end up going that route) but that could get shuffled to another spot.
 

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Starboard view;
 

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You definitely won't be driving a second alternator off that one belt. Most higher output alternators (130+ amps) use a heavier single belt, 2 belts, or a serpentine belt. Charging limitations vary from manufacturer to manufacturer. Trojan recommends a maximum of 13% of battery capacity. Would check with the manufacturer of your batteries before assuming 30%. Clearly you can push the limit somewhat provided the batteries are able to dissipate the increased heat from charging. This will likely shorten overall battery life. What amp alternator are you running now?

Ted
 
I'd just go with the largest alt that fits in the original alt spot. Rig an external regulator so output can be adjusted to right below where belt starts to squeal. Should be able to get around 100a if you rev engine to 1800 or so.

Just seen too much mechanical misery by added second alts.

Optimize the single alt arrangement you have and it will get you close to where you want to be.
 
Larry M said:
Sorry RT, but the engine's the Dover, FL SP135 not the 120. No mods were made other than adding the other alternator/bracket. The main pulley was on the boat when we bought her.
Click to expand...

Me too, well almost.

I got the bracket from American Diesel. I wanted faster charging times. After only one night on anchor, I would be -400 amp-hours, which would then take the 120 amp Balmar Alt 8 hours to replace.

But was running out of time in Florida to get it done. Kept reading about positives and negatives of dual alternators. :confused:

Ran out of time in Florida to get it done. But did get the solar pane;s installed and changed my 120v fridge and freezer.:D

On the way north, I noticed with the solar panels putting about 40+ amps back in every day and the new Vitrifrigos only taking 150 amps/24 hours at absolute most. My worst nighttime deficit was not more than 100 amps, which then got put back with only a few hours of running.:dance:

Decided i did't need no stinkin second alternator.:nonono::nonono:

But I did get a spare before i left RI:dance::lol:
 
Ski in NC said:
I'd just go with the largest alt that fits in the original alt spot. Rig an external regulator so output can be adjusted to right below where belt starts to squeal. Should be able to get around 100a if you rev engine to 1800 or so.

Just seen too much mechanical misery by added second alts.

Optimize the single alt arrangement you have and it will get you close to where you want to be.
Click to expand...

:thumb::thumb:
 
Ski in NC said:
I'd just go with the largest alt that fits in the original alt spot. Rig an external regulator so output can be adjusted to right below where belt starts to squeal. Should be able to get around 100a if you rev engine to 1800 or so.

Just seen too much mechanical misery by added second alts.

Optimize the single alt arrangement you have and it will get you close to where you want to be.
Click to expand...

+1, and stay within the engine manufacturer's specifications for accessory power required and side loading on the crankshaft. :thumb:
 
Ski in NC said:
I'd just go with the largest alt that fits in the original alt spot. Rig an external regulator so output can be adjusted to right below where belt starts to squeal. Should be able to get around 100a if you rev engine to 1800 or so.

Just seen too much mechanical misery by added second alts.

Optimize the single alt arrangement you have and it will get you close to where you want to be.
Click to expand...

That's my advice as well. He already has an 80 amp alternator. I have twice the battery bank that he has and only once have I ever seen it charging above 80 amps. If he can adapt a 3 stage regulator to his existing alternator that would be the simplest and most cost effective way to increase his charging while at anchor. You could throw a lot of money at this and not gain much more as far as charging ability. Increasing the size of the battery bank would also be helpful if he has room.
 
DCBD said:
That's my advice as well. He already has an 80 amp alternator. I have twice the battery bank that he has and only once have I ever seen it charging above 80 amps. If he can adapt a 3 stage regulator to his existing alternator that would be the simplest and most cost effective way to increase his charging while at anchor. You could throw a lot of money at this and not gain much more as far as charging ability. Increasing the size of the battery bank would also be helpful if he has room.
Click to expand...

Home for lunch, so not much time, just wanted to say thanks for everybodies input. Since I'm at the bottom of the learning curve all this wandering around checking out different possibilities has hardly been a waste of time...so much to learn!

Will commit to finding out how to squeeze as much as I can out of one alternator (probably with the serpentine belt kit linked above) after checking Yanmar for side loading on shafts and Exide's charging recommendations, while keeping in mind pulley sizes and engine rpm.
 
This is my set up . It was installed by the PO . Electrical is not my strong point so I can't tell you much about it.
 

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