Alternators - leave them alone and forget about them

[Jeff F]

I've been following the challenges that come with adopting lithium for a long time. By far the most intractable challenge has been hooking them up to the alternator.

I have a solution. Don't. Leave the OEM alternator charging the start battery and look elsewhere for charging sources for the house bank.

Let's assume you have a lithium house bank sized to accomodate 24 hours typical use.

I can think of three viable ways to charge the house bank away from the dock. Alternator, genset through AC charger, and solar.

None of these are any better or worse for the battery. The charge cycle doesn't have to match the discharge cycle. There is no necessity in achieving or maintaining full charge, and no practical constraint on charge rate. Lithium is liberating that way.

It seems to me you can pick any two out of three charging sources and get on with life. If you're optimizing for liveaboard at anchor you've learned to do without alternator input. Why not give it up completely?

Go ahead. Shoot me down. But honestly I'm tired of the alternator angst when maybe we can just not go there. Not going there might be easy.

Tell me again why charging from the engine is a good idea. We needed it way back when, but now? Why do we treat it as a necessity? My Prius had a 12v start battery but no alternator. Let's be a little creative.

[Simi 60]

It's not just LFP
I smoked two large frame alts (one on warranty) doing AGM house bank

Now the replacement does starts only with a small 24v Victron charger to finish off and condition
Big solar and Genset if required does house, now LFP.

[rslifkin]

I don't feel the need to have high capacity charging from my alternators, but some is necessary. It helps power the windlass (run from the house bank) and my electronics are all powered from the house bank. So with no alternator input, I'd just be drawing the batteries down if I run at night when there's no solar input.

The other time I appreciate alternator charging is if we've had cloudy weather and are down on power, but going to move the boat. The extra fuel burn from higher engine load for more alternator demand is less than I'd burn by firing up the generator for a couple hours to throw a similar amount of power into the batteries.

[Jeff F]

Originally Posted by rslifkin

The extra fuel burn from higher engine load for more alternator demand is less than I'd burn by firing up the generator for a couple hours to throw a similar amount of power into the batteries.

I can see the increased fuel burn in my instrumentation when I load up the alternator. I suspect the increased fuel burn would be similar to that used by a genset charging. Lithium supports bulk charging nicely. Any efficiency argument is going to be over small differences.

[O C Diver]

Ok, let me give you my reasoning.

When I set my boat up 8 years ago, my parameters were pretty simple:

I would anchor most of the time while cruising.

I wanted the lowest cost method to charge the bank while motoring.

I wanted atleast 2 totally independent ways to charge the bank, regardless of weather and time of day.

My solution was to be able to charge the bank through the inverter / battery charger, powered by the generator or shore power. The primary source is through the alternator.

So why is the alternator the best choice while cruising? On my boat, I added a purpose modified and optimized second alternator. Between the alternator, external regulator, and installation, I invested around $1,000. As I did most of the installation myself, it might cost someone else around $2,500. I now have 7 years of cruising on the boat with 5,000 engine hours. In that time, I have done ABSOLUTELY ZERO MAINTENANCE to the alternator. I haven't even replaced the serpentine belt that drives it (haven't even adjusted it). My 5K hour PM will be to replace the brushes, bearings, and belt. Tell me how many hours of generator time you would have to rack up to equal that amount of charging? BTW, my alternator is 220 amps and the battery charger is only 120 amps. How many hours and dollars of maintenance will be required? When I use the alternator, there is zero engine maintenance above what is required to push the boat. Lets talk efficiency. If running a generator to power a battery charger, there is wasted energy to make the generator engine run. There is no extra energy required for the boat engine as it's already required to push the boat through the water. So in essence, the alternator only requires the energy to make electricity. Finally, if you use an alternator to charge a battery, it doesn't require a power conversion. Running the generator to run a battery charger requires another power conversion. Power conversions aren't 100% efficient.

This year I cruised for 7+ months. I put around 120 hours on the generator, most of the time for climate control. I would guess it could have been between 500 and 750 hours without the second alternator.

Ted

[Jeff F]

Ted, I've always had lots of respect for your choices and rationale. Your use case and mine are remarkably similar.

I guess for me the game changer is lithium and solar. If I hadn't adopted both I'd be echoing your points. So maybe I'm really advocating for more solar. In any case these two changes for me have changed the way I look at house power management.

I can't fault any decisions you made 8 years ago. But what would a do-over look like in today's world? You can go for endless redundancy, but that's a want rather than a need.

[O C Diver]

Originally Posted by Jeff F

Ted, I've always had lots of respect for your choices and rationale. Your use case and mine are remarkably similar.

I guess for me the game changer is lithium and solar. If I hadn't adopted both I'd be echoing your points. So maybe I'm really advocating for more solar. In any case these two changes for me have changed the way I look at house power management.

Please explain to me why Lithium makes any difference regarding the charging system. There are external regulators that can be programed for Lithium. I would have thought one of the advantages to a second alternator with Lithium would be the high amperage rate (up to 320 amps at 15 volts) and bulk charging format.

I can relate to solar's zero fuel cost. Without building a bank that would last 3 or 4 days, I wonder how many days would require generator time while cruising in the Great Lakes. While it would be nice to have some solar, my pilothouse roof just doesn't have the space for it, so it was never really a serious consideration.

Ted

[Jeff F]

Actually I shouldn't have asked. You've got a great setup that's matched to your use case. Carry on.

[Jeff F]

Originally Posted by O C Diver

Please explain to me why Lithium makes any difference regarding the charging system. There are external regulators that can be programed for Lithium. I would have thought one of the advantages to a second alternator with Lithium would be the high amperage rate (up to 320 amps at 15 volts) and bulk charging format.



I can relate to solar's zero fuel cost. Without building a bank that would last 3 or 4 days, I wonder how many days would require generator time while cruising in the Great Lakes. While it would be nice to have some solar, my pilothouse roof just doesn't have the space for it, so it was never really a serious consideration.



Ted

I have 7.5 kw of lithium, with 700 watts on top of the pilot house, shaded at times by the radar and mast.

I didn't keep detailed stats, but I'd estimate average daily output Jun-Aug at 2.5 khw/day.

My summertime house consumption matches that pretty closely. I have modest needs.

Both vary, of course. But with enough capacity for 2 days and a lithium battery you learn to relax when you're running at 50% and check to see whether it'll be nicer tomorrow. It's liberating.

I think if you carefully examine your use case you might see that bulk charging capabilities become needless with lithium. It's a bit paradoxical. You can do it, but maybe you shouldn't.

[O C Diver]

Originally Posted by Jeff F

I think if you carefully examine your use case you might see that bulk charging capabilities become needless with lithium. It's a bit paradoxical. You can do it, but maybe you shouldn't.

It's interesting to think what I might change in the future when switching to Lithium, but the reality is that I'm probably not going to own the boat when the batteries need to be changed next.

Ted

[Jeff F]

Originally Posted by O C Diver

It's interesting to think what I might change in the future when switching to Lithium, but the reality is that I'm probably not going to own the boat when the batteries need to be changed next.



Ted

Right. Not advocating change for you.

I think you built your existing system around the needs and capabilities of LA batteries. The new generation of batteries is much more flexible and tolerant, so it's worth a rethink. It requires unlearning what you have learned :-)

[Simi 60]

Originally Posted by Jeff F

I have 7.5 kw of lithium, with 700 watts on top of the pilot house, shaded at times by the radar and mast.

I didn't keep detailed stats, but I'd estimate average daily output Jun-Aug at 2.5 khw/day.

My summertime house consumption matches that pretty closely. I have modest needs.

Both vary, of course. But with enough capacity for 2 days and a lithium battery you learn to relax when you're running at 50% and check to see whether it'll be nicer tomorrow. It's liberating.

I think if you carefully examine your use case you might see that bulk charging capabilities become needless with lithium. It's a bit paradoxical. You can do it, but maybe you shouldn't.

Similar story for us but with 2.5kw of solar up top and 20kwh of lifepo4

I'd love on engine charging but not enough to spend the $3000 plus needed here in Oz

24v Balmar/wakespeed and the like are over $1000
A 24 volt large frame brand name alt that throws out 150+ amps will cost nearer $2000
Plus fitting

That buys a lot of Genset hours and all I need do there is press a button and turn a key and run it for a hour or two every few weeks when it rains.

[DDW]

It all depends on the use case doesn't it? If you are in the PNW anchored out every night, the AC line charger and solar aren't going to cut it. If you don't like listening to the drone of the genset, that isn't the answer either. If you typically run 4 - 6 hours a day between anchorages, then the alternator is the ideal charge source. Engine already running, alternator probably already needed.

The reason boats are set up so many different ways isn't because the 3/4 that didn't do it your way are wrong - it might just be wrong for them.

[Insequent]

Jeff, your "choose two of the three" is reasonable.

Ten years ago I did a major refit at Port Townsend and the result in terms of electrical energy was:
1. Discard Onan 7.5 kVA genny
2. 200A Leece Neville alternators on each engine, Balmar regulator. OEM alternators on new JD engines were sold.
3. 1820 W solar, in 7 panels
4. AGM house bank of 1284Ah @12V (Odyssey PC1800FT) charged first, with ACR's to start batteries

I was very happy with performance in general, but after 5 years I tweaked the solar setup. I configured 6 panels of higher wattage, mostly to reduce shading. I then had 2070W. Shading absolutely is a killer.

The alternators have been flawless. I bought a spare at the time, but have never needed it, or replaced serpentine belts. With a depleted house bank I was seeing 360A going into the AGM's. No way would a flooded wet acid bank of similar size been able to take it. Obviously temp sensors on the alternators, and they de-rate if getting hot. But they put a lot of AH back into the batteries in the first part of bulk charge. No reason to ever smoke an alternator IMO.

A year ago I tweaked the solar setup again, mostly by adding 2 more panels and having 4 of the 8 panels on stainless drawer slides. When utilised, the slides further reduced shading. I now have 2740W of solar. I added a timer switch to heat hot water once the house bank is at 90% or so. In summer I have excess solar capacity, but in winter or with several cloudy days I may have to consider pulling out the Honda 2000 portable genny. Although in practice I'll just raise the anchor and motor for an hour or two to another spot.

At the time of the latest solar tweak I installed 3 x 300Ah lithium batteries. We programmed the Balmar reg with correct voltages etc, and de-rated the alts a touch on the basis that the lithiums would be able to suck higher amps than the AGM's for longer, and that might stress the alts unreasonably. On testing they can still put out 340A between them, which is a decent charge rate.

I have AGM start batteries. So we disabled the House/Start ACR. In practice it was a manual turn off in the ER and labels on the ACR there, and on the remote switch at the helm. Labels indicate that the ACR is for emergency use only. To charge the start batteries, each has a 30A Victron DC-DC charger. Source house lithium and destination AGM start. Some may say I'm vulnerable to a failing AGM start battery. But anyone using a shore power charger has the same vulnerability. Bottom line is that you have to be diligent when a lead acid battery is being charged.

I don't miss the Onan at all. I should note that I don't have aircon. If I did, a genny would be needed. Then I'd be at 3 out of 3, but who cares?

Were I starting again with a blank sheet I would still go for large alternators and as much solar as could reasonably be fitted

[Jeff F]

Originally Posted by DDW

It all depends on the use case doesn't it? If you are in the PNW anchored out every night, the AC line charger and solar aren't going to cut it. If you don't like listening to the drone of the genset, that isn't the answer either. If you typically run 4 - 6 hours a day between anchorages, then the alternator is the ideal charge source. Engine already running, alternator probably already needed.

The reason boats are set up so many different ways isn't because the 3/4 that didn't do it your way are wrong - it might just be wrong for them.

Check daily consumption against charge rate of generator/charger. Optimize charger size. That gives you the hours per day of drone requirement. With a three day capacity you can be very selective of when you drone. Motoring is optional and independent.

How's that bump against your use case?

[Jeff F]

I don't have a way, for the record. I'm a problem solver hanging out on my boat, experimenting and learning. And it's January.

I'm married to a philosopher. So maybe I come off as arrogant and challenging. I'm not really advocating, just sort of challenging conventional wisdom a bit.

[Simi 60]

I'll bring this thread up again as it has big similarities

What I was proposing was a belt driven AC 10kw MeccAlte generator head which is similar in size to an alternator and available for $500 .
Wired into the inverter charger to, on our boat, provide 120amps of charge.
Could have an electric clutch to turn on and off

Our vessel spends 99% of her time running constant RPM.



https://www.trawlerforum.com/forums/...ger-62840.html

I haven't looked at it further as we have big solar and Genset.
But if the Genset dies I would seriously look into this again.
There has to be a way.....

[Jeff F]

Originally Posted by Simi 60

There has to be a way.....

Of course there's a way, but what's the motivation?

The only possible motivation would be if you had no genset. Back to 2/3.

If you're going to maintain a genset you shouldn't be afraid to use it to do charging vs. engine. Pick your poison.

[DDW]

Originally Posted by Jeff F

Check daily consumption against charge rate of generator/charger. Optimize charger size. That gives you the hours per day of drone requirement. With a three day capacity you can be very selective of when you drone. Motoring is optional and independent.

How's that bump against your use case?

Just to show that there are many cases: I own a sailboat and a trawler. They are very different. The sailboat does not have a genset at all, just a very large alternator (280A @ 24V). I would prefer not to run the engine at all. There is only space on deck for 500W of solar, which is guaranteed to be half shaded. I have about 3 days capacity in the battery bank, then the engine must be run. It needs to charge the battery as fast as possible.

The trawler gets run about 4 - 6 hours every day we are on it pretty much, batteries are charged by the alternator. In 3 years I have put about 10 hours on the genset. Consumption is about the same (in both cases, refrig and freezer are the main consumers).

No matter what your fuel consumption says, a genset is a very expensive and noisy way to recharge batteries. On the trawler the main engine is already running, putting out about 1/5 its rated power. The additional load of the alternator is very efficiently driven. On the sailboat a genset will cost substantially more than the main propulsion engine, it makes no sense to have one at all.

On the other hand a power boat anchored in a bad climate might need to run the genset to keep the AC alive. Whole different scenario.

It's easy to fall into the trap of looking only at your own boat and usage. The reason there are so many ways to set up a DC system is that no one way is good for every case.

[Jeff F]

Originally Posted by DDW

Just to show that there are many cases: I own a sailboat and a trawler. They are very different. The sailboat does not have a genset at all, just a very large alternator (280A @ 24V). I would prefer not to run the engine at all. There is only space on deck for 500W of solar, which is guaranteed to be half shaded. I have about 3 days capacity in the battery bank, then the engine must be run. It needs to charge the battery as fast as possible.

I too have a sailboat, and have the same concern and solution. That's heavy necessary optimization on a single charge method. Your engine is equal part propulsion and generator. Clearly out of scope here.

On the other hand a power boat anchored in a bad climate might need to run the genset to keep the AC alive. Whole different scenario.

So you have a genset but don't use it regularly. And solar isn't in the mix. You have 2/3 and are optimizing on one for obvious reasons.

But assuming a decent size lithium bank you don't need a big honking generator. There is zero benefit in having the batteries fully charged by lunch time. Depending on typical house needs a dc-dc charger may be an appropriate solution.