Upgrading Generator Alternator for House Bank

I have been working on improving my electrical systems and it strikes me that if I'm out on the hook a lot, without much solar... I'm running my generator to drive my charger converting energy twice which seems inherently inefficient.

Wondering what folks thoughts are on installing a high capacity alternator with multi-stage regulator on the generator? I have a 3cyl westerbeke 8kw diesel generator. This is an oversized generator for the boat (shore power is only 6kw) rarely do we demand more than 4kw from it.

Probably not going to be a significant savings unless you have a smaller battery charger. How big is your current battery charger? How big is your battery bank?

Ted

Both are too small 50A/250AH. Just have not prioritized upgrades yet there hence the question.

I am not sure size is a factor here tho, as I cannot imagine ever having a shore charger larger than what is obtainable in terms of an alternator.

maybe break this down into 2 questions, is alternator to batteries more efficient than generator to charger to batteries?, and two, is it practical to stick a high output alternator on a westerbeke like mine?

kev_rm said:

I have been working on improving my electrical systems and it strikes me that if I'm out on the hook a lot, without much solar... I'm running my generator to drive my charger converting energy twice which seems inherently inefficient.

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Doubt I'd bother with the cost and effort to fool with it. Might be some slight inefficiency in your current set-up, but that probably wouldn't be enough to overcome my resting inertia.

Our genset alternator charges the genset start battery, and at the same time generator output to the chargers to the batteries is max bulk/absorption current our charger will provide and batteries will accept. If the chargers were larger (within reason for the battery banks), our set-up would be more efficient... but even that probably wouldn't get me off the dime unless/until a charger needs replacing because of failure. Or if I have so many surplus boat bucks$$$ hanging around, I can't think of anything else to do with them.

In fact, one of our projects last year was slightly about that. (Finally had some boat bucks$$$.) We added an inverter/charger to service one whole bank... so now each large bank has it's own dedicated charger and therefore overall max current to both improved... to take advantage of the AGMs. But that whole project was about gaining an inverter (and all those benefits) and a charger, not a minor detail like a larger alternator.

-Chris

Kev

Do you have a dedicated battery for your genset?

Is so and just for grins, price out an alternator that is dedicated for the genset start battery. That would provide some redundancy in the event of other charger issues.

I'd upsize the AC powered charging system over installing a larger DC alternator on gen engine. Installing a big alt on that thing is mechanically problematic. Alt regulator to be effective will be expensive. Efficiency of conversion is a very minor issue, and if you ran through all the math the alt may in fact be less efficient. And the larger charger is available for use when shore power is available.

kev_rm said:

Both are too small 50A/250AH. Just have not prioritized upgrades yet there hence the question.

I am not sure size is a factor here tho, as I cannot imagine ever having a shore charger larger than what is obtainable in terms of an alternator.

maybe break this down into 2 questions, is alternator to batteries more efficient than generator to charger to batteries?, and two, is it practical to stick a high output alternator on a westerbeke like mine?

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First issue is what type of batteries you have. If you have golf cart wet lead acid batteries, depending on the manufacturer, you should only be charging them at around 20% of capacity or 250AH x 20% = 50A. If you decide to charge at a higher rate, it seriously kills battery life. Obviously, other battery types can accept higher charge rates.

It costs me between .4 and .5 GPH to generate 14.8 volts at 200+ amps with my 220 amp alternator with Sterling 3 stage regulator on my John Deere. That's around 3KW for comparisons purposes.



Depending on the size of the alternator, pulley(s), belt(s), and fabrication, you could invest a fair amount of coin. My system including alternator, 2nd crank pulley assembly, external regulator, and some fabrication labor was probably $1.5K to $1.8K. 100 amp alternator in this setup might have cut the cost in half.







Ted

It's an interesting questions; what is the relative fuel efficiency of generating power from a genset vs an engine mounted alternator. I did a little experiment last summer and have been meaning to write a blog article with the results. Maybe this will get me off my butt. The simple answer is, it depends.

More specifically to this post, you will encounter some losses and limitations with an engine mounted alternator, in this case your generator engine.

- There are limits on how much power you can draw off the pulleys on an engine vs the main output off the flywheel. It varies, but 10% of rated power is a number I have seen thrown around. That means no more than 800W on your 8kw genset. Or maybe tops 1600W if the engine can handle up to 20%.

- There are power losses in the belt drives for alternators. This reduces fuel efficiency. How to quantify it? I don't know.

- There are electrical conversion losses in the alternator. We often thing in terms of the DC output that goes straight into the batteries and think that's efficient. But what many don't know is that the alternator actually generates 3-phase AC power which is then rectified into DC with diodes in the alternator. These dissipate a lot of heat which translates into loss of efficiency.

So it really isn't a given that generating power from an engine mounted alternator is more efficient than from a genset.

Personally, I agree with Ski. If I was going to do anything, I would add more AC charging capacity and load up the generator that way.

Thanks all good advice.. had not considered the mechanical and fitment type issues so obviously not a slam dunk as opposed to just eating any conversion that the charger does. (now understanding those may not even be material).

I'm kind of in an interim state right now and future will include enough solar to not need too many top offs. I actually dislike generator to battery in any form because no one ever runs them long enough to get a good absorption phase in any case..

kev_rm said:

Thanks all good advice.. had not considered the mechanical and fitment type issues so obviously not a slam dunk as opposed to just eating any conversion that the charger does. (now understanding those may not even material).

I'm kind of in an interim state right now and future will include enough solar to not need too many top offs. I actually dislike generator to battery in any form because no one ever runs them long enough to get a good absorption phase in any case..

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Maybe think of solar the other way. If you did the bulk and much of the absorption charge in the morning, maybe you could get a more complete charge during the day with solar. Other than refrigeration, during the day there is very little else sucking off the battery when your at anchor.

Just a thought.

Ted

twistedtree said:

It's an interesting questions; what is the relative fuel efficiency of generating power from a genset vs an engine mounted alternator. I did a little experiment last summer and have been meaning to write a blog article with the results. Maybe this will get me off my butt. The simple answer is, it depends.

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OK, I got off my butt (or more accurately I sat on my butt) and wrote the blog article that I alluded to on this topic

Adventures of Tanglewood: Engine Alternator or Generator: Which is More Efficient?

I long ago suffered battery charge issues. I even purchased a Xantrex 50 amp charger....... will not express my regards to this *^%$# other than to say it was an unwise expenditure.

I tired of having to run a 7.5KW generator for 6 hours a day on anchor AND STILL HAVE LOW BATTERIES. I finally went solar. First I purchased a pair of 150W panels that almost resolved my problem so the next year I purchased another pair. There is charging current from the time the sun rises to mid afternoon when the batteries ( 4 each East Penn golf carts) wired as one 12v bank is fully charged.

This arrangement gets 24 amperes into the batteries for hours until the batteries are charged or the sun fades. NO MORE BATTERY PROBLEMS! We run a 2KW true sinewave inverter 24/7 so we always have AC on the boat while away from the dock. The inverter runs at the dock also in case of power outages.

For load on the batteries..... microwave oven as needed, 2 32" HD TVs, toaster, 2 laptops, lights plus an 8.3cuft fridge with self defrost and an interior light not found in marine fridges.

If you have space for panels I highly suggest solar! Why screw around with alternatives that you will not be happy with. 150 watt panels are available today for $150 delivered. I have 4 panels, last fall installed another hard top, this time over the helm. I am arguing with Self about purchasing another pair or two pairs. Heck, the only reason would be for hot water so........

twistedtree said:

OK, I got off my butt (or more accurately I sat on my butt) and wrote the blog article that I alluded to on this topic

Adventures of Tanglewood: Engine Alternator or Generator: Which is More Efficient?

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OK, my intention is not to challenge your analysis but to highlight what I consider somewhat important.

Alternator armatures are wound with copper wire which has a positive temperature coefficient. This means that current flow through the wire generates heat and the hotter it gets, the higher the resistance which means the hotter it gets the.............

I have no clue how you can operate an alternator at currents significantly over 100 amperes for any length of time without cooling, forced air or water. Your generator I am supposing is in the bilge where air flow is constrained coupled with no fan on the engine.

But assuming some how you do get the currents you describe for extended time periods, I suggest that inverters, especially those designed to operate at 120 or even 240vac can easily output huge DC currents for battery charging. And batteries should be temperature monitored when being charged at high rates to prevent over heating. Just my humble thoughts

fog, I don't think inverters output DC Are you talking about an inverter charger? That's just a charger when it has AC input.

I would agree, however, on the very large output (>150A) alternators are questionable - but for my purposes 100A is about as big as I would need. Don't watch TV, fridge is largest load.. just need to power some LED lights and a laptop and mifi/wifi booster beyond that.


Tangle's analysis is great, I love actual data - but in the case of my question, I am basically considering adding a an additional alternator load to a generator engine already loaded up... so I actually think there could be an advantage to using a larger (100A) alternator over an AC powered charger or inverter/charger. I was not suggesting charging the house bank with a large ME while on hook.

kev_rm said:

fog, I don't think inverters output DC Are you talking about an inverter charger? That's just a charger when it has AC input.

I would agree, however, on the very large output (>150A) alternators are questionable - but for my purposes 100A is about as big as I would need. Don't watch TV, fridge is largest load.. just need to power some LED lights and a laptop and mifi/wifi booster beyond that.


Tangle's analysis is great, I love actual data - but in the case of my question, I am basically considering adding a an additional alternator load to a generator engine already loaded up... so I actually think there could be an advantage to using a larger (100A) alternator over an AC powered charger or inverter/charger. I was not suggesting charging the house bank with a large ME while on hook.

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Kev--- whatever floats your boat

But consider this URL for a starting point, there is a bunch of products that might meet your requirements

http://www.invertersupply.com/index...F8XWtS86kYE1REY7N3nYC8-dv3bm3MVsLcRoCesLw_wcB

foggysail said:

OK, my intention is not to challenge your analysis but to highlight what I consider somewhat important.

Alternator armatures are wound with copper wire which has a positive temperature coefficient. This means that current flow through the wire generates heat and the hotter it gets, the higher the resistance which means the hotter it gets the.............

I have no clue how you can operate an alternator at currents significantly over 100 amperes for any length of time without cooling, forced air or water. Your generator I am supposing is in the bilge where air flow is constrained coupled with no fan on the engine.

But assuming some how you do get the currents you describe for extended time periods, I suggest that inverters, especially those designed to operate at 120 or even 240vac can easily output huge DC currents for battery charging. And batteries should be temperature monitored when being charged at high rates to prevent over heating. Just my humble thoughts

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Please chime in, by all means.

You are right, I didn't make any assessment of the heat from the windings. Both the alternator and generator end will produce such heat, and I expect it will be higher in the alternator because of the higher current.

All the generator ends and alternators that I've seen have forced air cooling. It's typically part of the pulley on an alternator and internal to the generator end. Like you said, there is a lot of heat to pull out. I have seem my alternator case go as high as 300F which is too high. I actually made some mods to the protective shroud to allow for better air flow and it now runs much cooler - typically low 200F range. The alternator is designed for full output continuous duty, and yes, it runs hot.


Like most boats, I can charge my batteries via my alternator or via shore or gen power and a variety of chargers. The alternators (there are two running in tandem) can put out about 275A, and my AC powered chargers can put about about 270A. So both charge sources can crank out around 7.5kw of power. That's enough to load the generator enough to be efficient, or to charge strictly from the alternators. I can also run my washer and dryer off the alternators via inverters.

All that is what got me wondering just which was best to use when, and how much it really mattered, if at all.

Oh, and all chargers have battery temp sensors as you suggest.

kev_rm said:

fog, I don't think inverters output DC Are you talking about an inverter charger? That's just a charger when it has AC input.

I would agree, however, on the very large output (>150A) alternators are questionable - but for my purposes 100A is about as big as I would need. Don't watch TV, fridge is largest load.. just need to power some LED lights and a laptop and mifi/wifi booster beyond that.


Tangle's analysis is great, I love actual data - but in the case of my question, I am basically considering adding a an additional alternator load to a generator engine already loaded up... so I actually think there could be an advantage to using a larger (100A) alternator over an AC powered charger or inverter/charger. I was not suggesting charging the house bank with a large ME while on hook.

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Yes, I get that you are proposing something different, but I think the data still applies. You just happen to be powering the alternator off the generator engine rather than the main engine. I think as long as your generator is reasonably loaded, which it is, it will be just as efficient, and probably more efficient, to load up the generator engine via its AC end powering a charger rather than loading up its front pulley with a belt drive alternator. Plus I think the charger will be cheaper, much easier to install, and much easier to cool properly. And you won't introduce the potential to stall your generator by having the alternator load plus a larger than planned AC load (your alternator load will correspondingly reduce you generators AC output capacity)

twistedtree said:

Please chime in, by all means.

You are right, I didn't make any assessment of the heat from the windings. Both the alternator and generator end will produce such heat, and I expect it will be higher in the alternator because of the higher current.

All the generator ends and alternators that I've seen have forced air cooling. It's typically part of the pulley on an alternator and internal to the generator end. Like you said, there is a lot of heat to pull out. I have seem my alternator case go as high as 300F which is too high. I actually made some mods to the protective shroud to allow for better air flow and it now runs much cooler - typically low 200F range. The alternator is designed for full output continuous duty, and yes, it runs hot.


Like most boats, I can charge my batteries via my alternator or via shore or gen power and a variety of chargers. The alternators (there are two running in tandem) can put out about 275A, and my AC powered chargers can put about about 270A. So both charge sources can crank out around 7.5kw of power. That's enough to load the generator enough to be efficient, or to charge strictly from the alternators. I can also run my washer and dryer off the alternators via inverters.

All that is what got me wondering just which was best to use when, and how much it really mattered, if at all.

Oh, and all chargers have battery temp sensors as you suggest.

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My concern pertaining to wire heat is the insulation temperature class which manufacturers seldom provide. Formvar comes in various ratings, and of course there is crap out there.

At one time in the past I purchased a Generac 1KW generator because it was less expensive than a better grade Honda. The thing failed so I pulled it apart. It had a diac or triac forgot which that failed. So I soldered in a replacement and to my surprise, the soldering heat MELTED the wire insulation!

So sometimes when you open a box of chocolates you never know what is inside.

I have 2 x 200A Leece-Neville 12V alternators, one on each main engine. When installed we found they were getting hot, but some modification of the shroud/belt guard enabled the fan on the alternator pulley to provide enough cooling. I seldom see more than 350A going into the house bank (1284Ah AGM) when getting underway, but its enough!

My solar panels have input up to 160A as well. Yesterday at anchor the panels provided an average of 72.5 A for the 13 hours of daylight I had. As posted earlier, the best idea is to do your re-positioning move to new anchor locations in the morning, and let the solar take the batteries into absorption/float during the rest of the day. Of course that isn't always possible, but that's Plan A.

I don't have a genny anymore. Well, excluding a Honda eu2000. Which reminds me - I have not started it for over 4 months, I ought to do that.

foggysail said:

I tired of having to run a 7.5KW generator for 6 hours a day on anchor AND STILL HAVE LOW BATTERIES.

For load on the batteries..... microwave oven as needed, 2 32" HD TVs, toaster, 2 laptops, lights plus an 8.3cuft fridge with self defrost and an interior light not found in marine fridges.

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Seems odd. At anchor, we usually only ran the genset 4 hrs/day... to coincide with morning and evening cooking times... with 600 Ah of AGM battery in two banks... two fridges... and a measly little ol' 40 amp charger.

I wonder if that self-defrost feature (which we would probably like) is a serious power hog? I presume the interior light only comes on when the door is open? (But how would we know?)

kev_rm said:

fog, I don't think inverters output DC Are you talking about an inverter charger? That's just a charger when it has AC input.

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Notwithstanding our fairly decent charging results over the years... I wanted even more battery capacity if possible, and that in turn meant more/better charging capability. And we wanted an inverter of some sort to make quiet morning coffee and afternoon popcorn.

Turned out an inverter/charger on one of our battery banks could be a way to solve part of that... and increasing bank size should solve the other part of it. We installed the inverter/charger (70 amp) late last August -- so not much experience with it yet -- but it acts promising. Doing that meant we could devote the original 40 amp charger to one 300 Ah battery bank, use the 70A charger for the other 300 Ah bank...

And next, we'll change the 3xG31 dual-purpose bank -- the one serviced by the 70A inverter/charger -- to a 440 Ah deep cycle bank, with 4x GCs in series/parallel. That's space constrained, or I'd consider an even larger bank.

Bottom line, I'm hoping, is we get the inverter (already working) and more capacity at sorta-kinda the same time.

FWIW, even though I'd been thinking on that for several years... the installation location for the inverter was one hang-up. The other was about space constraints where the batteries live. Once I solved those, everything else could proceed apace.

And the two chargers, one 40A and one 70A, I think make better use of our 8 Kw genset anyway. Otherwise, when we're not running the ACs (aircons), we don't have much to put a decent load on it... except for probably the water heater, and even that's not much after the initial start-up.

I probably can't increase the size of the other bank, due to space limitations... but if the older (original) 40A charger craps out, I'd likely increase the size of that, too.... also to put a better load on the genset, and to take better advantage of the AGMs.

-Chris

Using the noisemaker to power a good sized alt is a great idea for most diesel cruisers.

A 135A alt can be had from a big truck store (like Detroit diesel) brand new for under $150 ($135 here in FL)

A big advantage is it frees up perhaps 10A on the small noisemaker for other uses.

And it usually creates a good load so the noisemaker cooling can heat a HW tank.

Yes you will need a proper 3 or 4 stage V regulator with temp sensor , but the combo will charge faster and harder than most AC powered battery chargers.

The last 10-15% of charge is still best with solar as the battery is the slowdown , not the DC source.

ranger42c said:

Seems odd. At anchor, we usually only ran the genset 4 hrs/day... to coincide with morning and evening cooking times... with 600 Ah of AGM battery in two banks... two fridges... and a measly little ol' 40 amp charger.

I wonder if that self-defrost feature (which we would probably like) is a serious power hog? I presume the interior light only comes on when the door is open? (But how would we know?)


-Chris

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Chris-- in post 12 I mentioned our illustrious 50 ampere charger which was just unable to recharge our batteries. The so called high output remained high for less than about 15 minutes instead of until the battery bank reached float. That forced me to seek a better charging technique....solar.

Now as to our fridge's light ..............well, I went years without a light using a marine fridge so just a little bragging!

We do use the genny for an hour or so in the mornings for hot water along with coffee. A genny though is nice for backup whenever needed.

But it won't fit on the engine in most cases. You would need to design and fab multiple brackets, extra pulleys, tensioners, etc.

What seems to be the objection for many to exclude solar? Why resort to mechanical means to charge batteries? Big heavy, hard to install alternators plus providing cooling for them? OK, I could not install solar onto my old 30 Hunter sailboat but this is a trawler forum with big boats and large available surface areas for most who post here.

I'm all for solar, but on my smallish boat there just is not much available space amenable to panel install. And in my normal cruising duty cycle batteries stay up just from running main engine from anchorage to anchorage.

In a one month cruise, I might run gennie for batt charging maybe a few hours total. A trivial expense.

foggysail said:

I tired of having to run a 7.5KW generator for 6 hours a day on anchor AND STILL HAVE LOW BATTERIES. ..

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Foggy, you must have some big power needs, small house bank and/or small chargers.

We are good for a day after about 45 minutes of gen set run time in AM and same in PM. We tie genset running in with washing/drying, cooking or raising anchor. When cruising for more than 4-6 hours or so our batteries are topped up from engine alternators.

Our house bank is 8 Trojan 105s with a 135 amp Magnum inverter charger. Engine starts have a 50 amp Newmar charger which can also feed house bank.

No argument with using panels, but for our cruising style no need.

sunchaser said:

Foggy, you must have some big power needs, small house bank and/or small chargers.

We are good for a day after about 45 minutes of gen set run time in AM and same in PM. We tie genset running in with washing/drying, cooking or raising anchor. When cruising for more than 4-6 hours or so our batteries are topped up from engine alternators.

Our house bank is 8 Trojan 105s with a 135 amp Magnum inverter charger. Engine starts have a 50 amp Newmar charger which can also feed house bank.

No argument with using panels, but for our cruising style no need.

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Our requirements are not abnormal. And it matters not how large one's battery bank is IF THE CHARGE CANNOT BE REPLACED while the boat is away from a dock.

Again.................... please read post #12 in this thread. The over rated battery charger I purchased based on literature FAILED to charge at or near 50 amperes until the batteries had attained float. Sure.... I could have gone forward, done additional research, purchased another battery charger and maybe depleted battery problems would have ended.

I had enough of the battery charger bullpoop and went with solar. There is no change, ZERO.... between the number of batteries before and after solar nor are there any changes in our power usage.

EDITED:

Solar works for those who have space for panels and IMHO is
(an absolute necessity for anybody)<--- change that to:

an absolute necessity for many

who spends time away from a dock.

Sorry for getting excited

I might agree if those boats stay at anchor in one spot all the time...but if underway every day or other day for more than a couple hours....then solar is NOT an absolute necessity.


Especially for vessels that run their gensets 24/7 for other reasons.


like many discussions here, rarely does one size or method fit all.

psneeld said:

I might agree if those boats stay at anchor in one spot all the time...but if underway every day or other day for more than a couple hours....then solar is NOT an absolute necessity.


Especially for vessels that run their gensets 24/7 for other reasons.


like many discussions here, rarely does one size or method fit all.

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Of course!!! I edited my post #27, Thanks PSNEELD

foggysail said:

Our requirements are not abnormal. And it matters not how large one's battery bank is IF THE CHARGE CANNOT BE REPLACED while the boat is away from a dock.

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Ok, you love your solar panels. And for you that was a better alternative than getting a beefy reliable inverter charger.

But, for many of us big reliable chargers are onboard with sufficient cruising hours done during the day to be battery state happy. If I anchored for days on end in a solar friendly area I'd load up the top with Elon's favorites.