Alternators - leave them alone and forget about them

rslifkin said:

On an 8 hour travel day, high amp charging is pretty unimportant unless you have high power draws while underway. But having the ability to charge faster is nice if you sometimes make a short hop to the next destination that's only an hour or 3 away. Of course, whether it's worth it depends on whether the faster charging is easy to implement or if it adds too much complexity.

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Right. And how important more capacity is in the future. It's an odd way to think about it. The promise of a future charge is equivalent to a charge now, until you run out of buffer.

rslifkin said:

On an 8 hour travel day, high amp charging is pretty unimportant unless you have high power draws while underway.

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Nope. See my earlier post. Irrelevant.

Hope my last comment made sense Rob.

In the real world, if I hit a six day patch of really gloomy weather at anchor and want to cook, I need to get traveling again, and not just across the bay.

I had one occasion last summer when I ran the engine specifically in order to charge. I had been at anchor a week or more on solar only, and was running low on juice. Gloomy dark weather late in the season. Rather than start the winterized genset I ran the motor for a couple of hours and was very thankful for the ability to charge at 130a.

But for me that's a highly anomalous situation. Normally if I pull anchor I'm putting in a long day. And if I end the day at 30% SoC I'm satisfied.

Edit to add: actually I've done that twice. Was at anchor in NS when the tail end of a hurricane blocked out the sun almost completely for 3 days.

rslifkin said:

Of course, whether it's worth it depends on whether the faster charging is easy to implement or if it adds too much complexity.

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And risk, I'd suggest. Not to mention cost.

Think through the failure case. BMS takes a wrong turn. Unrecoverable error.

If you've got your alternator hooked to the bricked battery it doesn't really matter whether it still works or not.

Assuming you've got operational needs covered, you carry on.

Now, if you have a generator you can support the operational side, assuming you have an AC 12v charger.

Solar is useless because it passed through house.

I'm not suggesting that this is a high likelihood event. TT has deep insight into the innards of his battery, and full failover capabilities. I want to use Chinese drop ins. Neither one of us is at particularly high risk.

I dunno. Seems like a no-brainer, for me at least.

This has been enormously helpful. Thanks to all.

Jeff F said:

Edit to add: actually I've done that twice. Was at anchor in NS when the tail end of a hurricane blocked out the sun almost completely for 3 days.

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But that was pre-lithium, so it doesn't count

cafesport said:

We have a pair of externally regulated 175 amp 24v alternators. Way more capacity than our batteries or hotel loads ever need or use. I’ve found that using our small generator instead of the alternators under way uses less fuel and keeps our engine room temp ten to fifteen degrees cooler. I pulled both alternators for rebuild at the 8000 hour mark just because. Not going to think about them ever again.

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I remember you mentioning this here a long time ago. At the time I was more Huh than Hmm. I get it now. Do you have lithium, or just run the generator all the time?

Jeff F said:

And risk, I'd suggest. Not to mention cost.

Think through the failure case. BMS takes a wrong turn. Unrecoverable error.

If you've got your alternator hooked to the bricked battery it doesn't really matter whether it still works or not.

Assuming you've got operational needs covered, you carry on.

Now, if you have a generator you can support the operational side, assuming you have an AC 12v charger.

Solar is useless because it passed through house.

I'm not suggesting that this is a high likelihood event. TT has deep insight into the innards of his battery, and full failover capabilities. I want to use Chinese drop ins. Neither one of us is at particularly high risk.

I dunno. Seems like a no-brainer, for me at least.

This has been enormously helpful. Thanks to all.

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I figure in the worst-case scenario like that, I re-configure things a bit to keep the important DC loads powered, and most likely crank up the generator and point the bow towards somewhere with shore power and the ability to get parts so I can get the system working again.

Thinking about the cloudy weather case, I think that becomes less of an issue as the boat gets bigger. Larger boats can often carry disproportionately more solar and battery, so it takes more cloudy days to become a problem.

For us, for example, we've got 820 watts of solar. Until the day comes that I ditch the bimini for a hard top, that's all we get as we're out of space to mount panels. It's enough in decent weather, but not when it gets really cloudy. And we still cook on generator power, as we don't have enough battery or solar to support using the stove on battery power full time (we can and at some point will add more battery).

Yeah, I could probably get up to 3+ kw without really giving anything up. It's one of the joys of a big pilothouse boat.

First I thought I'd carry the dinghy up top, then a Laser. There are two in my household. Now I'm thinking I could quite happily plaster it with panels.

Edit to add: more capacity also goes a long way. If you know that typical production > typical usage capacity makes you a winner, ultimately.

Given the price of cheap batteries that's probably a cheaper and more effective alternative to more solar. I can double my house bank from 3x daily use to 6x daily use with $2100 in batteries and a bit of cabling.

Jeff F said:

Yeah, I could probably get up to 3+ kw without really giving anything up. It's one of the joys of a big pilothouse boat.

First I thought I'd carry the dinghy up top, then a Laser. There are two in my household. Now I'm thinking I could quite happily plaster it with panels.

Edit to add: more capacity also goes a long way. If you know that typical production > typical usage capacity makes you a winner, ultimately.

Given the price of cheap batteries that's probably a cheaper and more effective alternative to more solar. I can double my house bank from 3x daily use to 6x daily use with $2100 in batteries and a bit of cabling.

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Even without going LFP I can easily double my house bank in the available space and without worrying much about weight. And eventually I'll install a hardtop which would give room for me to probably double our solar capacity.



At this point, my biggest sticking point for the eventual next battery replacement is whether it's time to go LFP or not. The costs are starting to look better, but I've still got a few sticking points to worry about (cold weather during winter storage, making sure my insurance doesn't have issues with LFP, etc.). And realistically, given enough solar, our usage patterns aren't particularly abusive to a lead bank, so I haven't had a pressing need to jump to LFP.

rslifkin said:

The costs are starting to look better, but I've still got a few sticking points to worry about (cold weather during winter storage, making sure my insurance doesn't have issues with LFP, etc.). And realistically, given enough solar, our usage patterns aren't particularly abusive to a lead bank, so I haven't had a pressing need to jump to LFP.

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My 300 ah drop ins are easy to heft around. If I ever store ashore in the frozen north I'll take them home and do some balancing and capacity testing.

They're a little over $1,000 each. If you want to go there it might be easier than you think...

And you're a planing boat. Weight matters!

Jeff F said:

My 300 ah drop ins are easy to heft around. If I ever store ashore in the frozen north I'll take them home and do some balancing and capacity testing.

They're a little over $1,000 each. If you want to go there it might be easier than you think...

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Jeff F said:

And you're a planing boat. Weight matters!

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Weight does matter, but as planing hulls go, this one carries weight pretty well. It's geared pretty low with good size props and doesn't have the "speed above all else" hull form that some do. Burning off 1500 lbs of fuel makes the boat faster at slow cruise by raising the stern, so there's less drag from the submerged transom. But oddly, other than popping onto plane a hair faster, there's no detectable speed difference on plane. The one thing that does slow the boat down noticeably is adding weight too far forward. We don't run on plane a lot anyway, so even the 500 lbs of batteries we'd be carrying aren't really an issue if I double the bank. And they're mounted fairly low and centered, so I can call them ballast to offset things like a hardtop.

As far as batteries, I've been looking at some of the heated drop-in options like the Kilovault ones that have CAN or other external communication for their BMSes. That's probably the route I'd take, as they could stay on the boat over the winter without issue. They won't see much use in storage, but it's nice to be able to plug the boat in and power up some basic systems when I'm doing work on things over the winter. It's mostly a matter of cost, insurance, and whether I find any systems changes needed (beyond alternator related ones) to do the swap.

Honestly, one of the biggest issues I'm running into is battery shape. I'm currently using the big, tall L16 6 volts. Most of the drop-in LFP options aren't nearly as tall, so fitting as much as I'd want in the available space might become a challenge. For example, the space that'll hold 4x L16 (830ah at 12v with AGMs, a little more with high end flooded batteries) is only able to hold a 400ah worth of the Kilovault drop ins due to not using the full height and the shape wasting a bit of space at the side of the area (but they're too long to install a 3rd oriented sideways).

The one thing I'd point out about the CAN thing is that once you've taken the bank out of the operational side and not fiddled with the alternators the need is minimal.

Jeff F said:

The one thing I'd point out about the CAN bus thing is that once you've taken the bank out of the operational side and not fiddled with the alternators the need is minimal.

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I'd want the integration with the Victron gear I have though (Cerbo, Multiplus, MPPTs). I have to do some more digging on those aspects of the system. But I don't like the idea of the BMS being all on its own with no control of anything else except to turn the batteries off entirely if it sees a problem.


Plus, I don't think I'd separate any of my loads off the house bank. I don't have huge operational loads when underway, and save for the engine room blowers, plenty of those loads get used at anchor as well (at anchor I normally leave a chartplotter on and the VHFs are on until bedtime).

rslifkin said:

I'd want the integration with the Victron gear I have though (Cerbo, Multiplus, MPPTs). I have to do some more digging on those aspects of the system. But I don't like the idea of the BMS being all on its own with no control of anything else except to turn the batteries off entirely if it sees a problem.

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Your choice. If you have multiple BMS in parallel the likelihood of a bank failure is vanishingly small.

twistedtree said:

So what's the concern over BMS disconnects? Well, a disconnect will only happen if the battery is operated out of allowed range for temp, charge voltage, etc. What's the solution? Just don't do it. In a correctly set up battery system, a BMS disconnect will NEVER happen.

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I've just reread the whole thread. Think it would be useful for anyone considering lithium.

This is where CAN or a smart BMS is a bit of a differentiator IMO.

In my choice to go cheap drop-in, I lose visibility into individual cell health. It occurs to me that the ultimate demise of my (individual) battery is not going to be predictable. If I had cell-level monitoring I'd be able to recognize a problem long before it manifested itself in a BMS shutdown.

But if you have a bank of them you have almost complete redundancy, and can swap out when they fail.

Jeff F said:

I If I had cell-level monitoring I'd be able to recognize a problem long before it manifested itself in a BMS shutdown.

But if you have a bank of them you have almost complete redundancy, and can swap out when they fail.

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Most of the drop in battery manufacturers now offer their batteries with bluetooth monitoring that can monitor each cell in each battery. Many have warnings as well. And they are still relatively inexpensive. Maybe $100 more each around the $400-$499 range for the typical 100AH "smart" battery.
I have made this part of my must have list for the drop in units I plan to buy.

I have Dakota Lithiums for my Golf cart and it drives me crazy that I cant see "into" them. I had one scenario where the center battery had a BMS shutdown that rendered the cart useless since its three 12volt/100Ah batts are configured in series. If one goes out the entire bank is done. But as you say this is not nearly as much of an issue with a parallel 12 volt bank.

Barking Sands said:

But as you say this is not nearly as much of an issue with a parallel 12 volt bank.

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Today it's a 20% premium in price. That will fall I'm sure.

I dunno. I did my time monitoring batteries in cars. At this point I'm happy to try the black box approach.

Jeff F said:

Today it's a 20% premium in price. That will fall I'm sure.

I dunno. I did my time monitoring batteries in cars. At this point I'm happy to try the black box approach.

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At times I do think we dissect these issues ad nauseum. I have stated here before...I am trying to stick to the 80/20 rule regarding nearly everything applicable to my boat.

The Pareto principle states that for many outcomes, roughly 80% of consequences come from 20% of causes (the "vital few").[1] Other names for this principle are the 80/20 rule, the law of the vital few, or the principle of factor sparsity.[2][3]

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You can drive yourself crazy (and spend a ton of money) trying to cover that last 20%.

I'm a techie, and big data is an interesting (and successful!) model. Rather than higher capacity processing and expensive storage, look to scale commodity capabilities.

Barking Sands said:

I had one scenario where the center battery had a BMS shutdown that rendered the cart useless since its three 12volt/100Ah batts are configured in series. If one goes out the entire bank is done.

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That would concern me. I've been sort of thinking of a 48v pack, and that would be one challenge. I'd definitely want cell level monitoring in that case.

Jeff F said:

I've just reread the whole thread. Think it would be useful for anyone considering lithium.

This is where CAN or a smart BMS is a bit of a differentiator IMO.

In my choice to go cheap drop-in, I lose visibility into individual cell health. It occurs to me that the ultimate demise of my (individual) battery is not going to be predictable. If I had cell-level monitoring I'd be able to recognize a problem long before it manifested itself in a BMS shutdown.

But if you have a bank of them you have almost complete redundancy, and can swap out when they fail.

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Exactly. The BMS makes disconnect decisions based on individual cell status, but outside the battery you can't see that. All you see is the sum voltage of all the cells. So a high terminal voltage on the battery is not predictive of when a high voltage disconnect will occur, and why you can't simply turn off your alternator based on battery voltage.


All it takes is a couple of wires coming out of the battery to give the rest of the system all the info it needs. A CANbus is definitely not needed, nor is bluetooth, an app, or anything else.



"Allow to Charge" (ATC) says it's OK to charge the battery. The installer uses that to enable/disable the alternator. Problem solved. It can (should) also be used to control other chargers, and protects against improperly configured chargers, charging when temps are too cold, etc. It's just one wire, and all of these integration problems are solved.



"Allow to Discharge" (ATD) says it's OK to discharge the battery, and can be used to shed loads.


And both of these signals serve as warnings of a possible approaching disconnect.


Regarding a parallel bank of drop-ins and the resulting redundancy, keep in mind that without any of the above signals, you won't know that one of your batteries disconnected. The system will keep running which is good, but you will be none the wiser that there has been a failure, and have no way to check or test without breaking up the battery bank to see if they are working individually. The only observable change will be a drop in battery bank capacity, and that might not be observable at all depending on your use pattern.


So I get the attraction to Drop-ins, but they do create a bunch of issues that have to be worked around like adding alternator protection, creating hybrid battery banks, or running all your alternator current through a DC/DC converter. And you lose fault indication and troubleshooting capability. So they seem easy, but actually create a lot of work.


On the other hand, if you use batteries and/or a BMS that has these simple signals, all of these integration problems become trivial.

Barking Sands said:

Most of the drop in battery manufacturers now offer their batteries with bluetooth monitoring that can monitor each cell in each battery. Many have warnings as well. And they are still relatively inexpensive. Maybe $100 more each around the $400-$499 range for the typical 100AH "smart" battery.
I have made this part of my must have list for the drop in units I plan to buy.

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This is great, but unless there are electric signals or contacts, it doesn't solve the integration problems. A warning on your phone, when and if you happen to look at it, if your bluetooth connection is actually working, isn't going to turn off your alternator in advance of a disconnect.


Victron's SmartShunt has reminded everyone how flaky bluetooth is. Its bluetooth connection from shunt to chargers has proven unreliable even when the components are in the same room and in close proximity.

twistedtree said:

Regarding a parallel bank of drop-ins and the resulting redundancy, keep in mind that without any of the above signals, you won't know that one of your batteries disconnected. The system will keep running which is good, but you will be none the wiser that there has been a failure, and have no way to check or test without breaking up the battery bank to see if they are working individually. The only observable change will be a drop in battery bank capacity, and that might not be observable at all depending on your use pattern.

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Right. That's still an outstanding issue for me. The ATC/ATD would certainly make that easy, but so too would a generic alert issued by the BMS. I can't think of a use for ATC/ATD in my system apart from that.

My batteries are individually cabled. I have to believe that there is a way to recognize when current stops flowing on a battery.

twistedtree said:

This is great, but unless there are electric signals or contacts, it doesn't solve the integration problems. A warning on your phone, when and if you happen to look at it, if your bluetooth connection is actually working, isn't going to turn off your alternator in advance of a disconnect.

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I think this concern is overblown for B.S. and me. Neither of us are charging with the alternator.

The only goal is to get a heads up when the battery is having difficulties. If in parallel that could just mean ordering a new battery and swapping out when convenient. If it disconnects in the interim it's no big deal. There is no real-time requirement.

Jeff F said:

I remember you mentioning this here a long time ago. At the time I was more Huh than Hmm. I get it now. Do you have lithium, or just run the generator all the time?

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We do have a small lithium bank appropriately sized for our solar charging capacity and matched to our agm tail current needs. We follow the ghostbusters rule to never cross the streams. The lithium bank also has its own separate charger for cloudy days if needed.

We spend close to a third of the year on the umbilical at home and run the engines an average of 600 hours per year, half of those hours the batteries start fully charged. Generator hours average 100/month. Once our agms get to absorb voltage the charge acceptance rate continuously decreases so charging via even a small genny becomes increasingly wasteful. That’s where our lithium bank gets put to work.

But since this thread is about alternators, I think we really need to consider how we each use our boats. Dividing last years engine hours by 8760 gives a glimpse into the percentage of time, not necessarily the amount of power, that was pushed into batteries while off the grid. That may or may not have been sufficient to handle the number of charging cycles your batteries need to live long and healthy lives. Looking at the frequency of battery installation ,maintenance and replacement threads on here, there does seems to be a pattern.

If you run can run enough engine hours each day doing the loop or island hopping your batteries should be very happy. Today’s solar technology in sunny locations is really tough to beat. For sailors hydro and wind generation keeps them off the cord and they no longer need to live like they are camping. Just look at the proliferation of sailing cats over the last 10 years. We all have different uses scenarios and electrical needs. What works for some might seem to be too much hassle for others.

twistedtree said:

This is great, but unless there are electric signals or contacts, it doesn't solve the integration problems. A warning on your phone, when and if you happen to look at it, if your bluetooth connection is actually working, isn't going to turn off your alternator in advance of a disconnect.

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But when using lets say...four 100AH bluetooth drop in units in parallel you dont need to disconnect the alternator if one battery has a bms shut down. Actually I might argue you dont want the alternator to shut down. You just carry on with 3/4 capacity in that moment. DO battery checks using bluetooth at various intervals (kind of like engine room checks) and deal with the situation when next able. This sounds perfectly reasonable to me. One caveat is the type of BMS reactivation. Some automatically reactivate after a time period. Some are locked out until a certain action is taken. Obviously in this scenario a full lock out is preferred. In addition an on/off switch on each battery would be preferable as well.

So a string of smart batteries in parallel that lock out upon failure and have separate on/off switches seems like a better option than some other arrangements where any bms failure will render not only the battery disabled but the alternator as well.
In this scenario you could have 3 out of 4 batteries fail and still continue without interruption to any system.

There are many scenarios where the cause of the BMS disconnect affects all the series drop-ins, and all disconnect either together or one after another. Paralleling them does not solve every issue. Another problem with drop-ins in a 24V or greater system is you have them in series. Without an external balancer, they can go out of balance in spite of the internal BMS balancer.

The thing that is missing from the whole galaxy of LFP solutions right now is the reliability and autonomous operation that is provided by LA. They are complex, and become your hobby to manage. AGM with current charging and regulation tech are an install and forget for many years prospect.

DDW said:

There are many scenarios where the cause of the BMS disconnect affects all the series drop-ins, and all disconnect either together or one after another. Paralleling them does not solve every issue. Another problem with drop-ins in a 24V or greater system is you have them in series. Without an external balancer, they can go out of balance in spite of the internal BMS balancer.

The thing that is missing from the whole galaxy of LFP solutions right now is the reliability and autonomous operation that is provided by LA. They are complex, and become your hobby to manage. AGM with current charging and regulation tech are an install and forget for many years prospect.

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I would submit that nearly every scenario where a string of parallel batteries would be simultaneously taken out would be a fault external to the batteries themselves and as such the batteries should probably be disconnected.

As for the 24 volt and greater issue...many manufacturers have 24, 36 and 48 volt options available as a single unit with single smart BMS. These can then be strung in parallel same as the typical 12 volt systems.

Your last paragraph I actually dont believe to be perfectly accurate. I think we tend to pour over the additional facets of LFP and smart this and BMS that and wring our hands a bit too much. I think in reality these batteries are proving to be equally reliable and in some cases more reliable. I myself have 3 lithium batteries and 4 AGM batteries. The only failures I recently have needed to address have been with the AGM's. Granted the AGMS were older. But they where also very difficult to detect as they were dying a slow, camouflaged death, causing the charger to output slightly more, vented corrosive gas in the bilge and when finally viewed with an infrared camera showed internal hot spots. AGM is a dumb battery and a single unit failure of a bank can be masked easily. It has a list of deficiencies all its own. As well as many positive attributes of course. But it took nearly a month to know that a single AGM was dying slowly. A bluetooth LFP would have been seen within a few hours. This last differentiation is actually part of the perception issues IMO. From our view the AGM failure is masked for long periods, lived with, goes undetected till it rises to a very noticeable level. The LFP failure is hard and fast and certain. For some these differences are unsettling.

One final thing. DDW and others....
Please understand these discussions, in my view, are not a contest. I view and participate in these discussions as a sounding board for interesting topics. My mind is always open for further revisions. And it is through these discussions that these views are "tested". Especially for a topic like this one where things are changing rapidly and not all is understood or quantified. I see these as running and continuous "thought experiments". Thanks for all the varying views and angles and thanks to JF for starting such a thread. It is very timely for me and many others.

forget about them

Jeff See PM
Regards