DC to DC charger - not needed for boats with proper alternators.

[skipperpete]

Originally Posted by CaptainRivet

Simple, you will pay for your lesson

Some just need to find it out the hard way

I learned that painful lesson with a set of Odyssey AGM’s and a conventional alternator.

[CaptainRivet]

Originally Posted by Jerry Woodward

My cat has two small diesels, 2GM20f and two alternators. About 4 yrs ago I upgraded one alternator to a Balmar 6 series 120 amp, a serpentine belt kit and a MC614 regulator (with the help of Main Sail). This really helped my lead acid bank, giving it a full charge when motoring. This season, I swapped the lead acid for lithium and wired the Balmar directly to the lithium bank and programmed the MC 614 appropriately with belt manager set to 3. I also have an alt protection device and alt temp sensor attached. This works very well and puts about 80-90 amps into the batteries for an extended period when I am underway. My other stock Hitachi alternator is wired to the start/reserve SLA battery. Thus, the reserve battery will maintain charge if I need to switch over to it. So, in my setup, I don't see the need for a DC-DC charger.

I assume you start your STB engine from lithium, typical cat setup. What happens if the STB doesn‘t work and you only have BB one. Means you cannot charge the house via alternator and you don‘t get a single amp in when BB is running.
I have the same setup STB with LFP starter+house but my BB engine with SLA starter has a 30A DC2DC charger so when BB engine running it’s charging the house too. Additionally I have a 9A DCtoDC from LFP to SLA to be able to charge the starter SLA if BB is not running.

[CaptainRivet]

Originally Posted by Fuss

My Leece Neville alternators both input into the 24v house bank and then dc to dc charge the starter battery. The boat has been no gas for 10 years with a 600ah battery bank. So sometimes the motor was running and cooking was happening so -150ah was on the battery monitor.

This must be very similar to charging lithium.

Well, I imagine that the alternators were at full power. I never did a temp test on them but I sometimes looked in the engine room and I never noticed burning smells. I have to think about this. I guess it didn’t run at -150ah for long. At this time I had battery temp sensing going to the alt regulators, now I changed to alternator temp sensing going to the alternator regulators.

That’s far from lithium charging, very far…
Before you notice a burning smell their rotor winding isolation lacquer is gone long before=alternator dead.

No the 24V leece Neville school bus alternators you most likely have fitted didn‘t run even close to full power as the high internal resistance and also the Peukert effect of the Lead physically limiting the current these alternators are able to deliver.

You have already one of the best available alternator fitted aftermarket = the rare species schoolbus alternator that are developed to run,on very low rpm’s and 24V=higher efficiency=less heat so they can run for a long time quite close to their rating but not many other can do this, certainly no OEM alternator is capable of running more then 60% of its rating for a long time. Most you are lucky if they can do 40%…

[s/v Jedi]

Originally Posted by CaptainRivet

I got that, otherwise you wouldn’t have swapped out 450A for 170A.
I am just curious why you didn‘t go with a 24V 90-100A alternator instead of a 12V 170A when you have a 24V house. Old yanmar means your engine doesn‘t need 12V for ECU so swapping the starter would be the only mod to go to 24V on the starter circuit too. More backup as you can start from house too and more efficient as your cables have less voltage drop.

Yes that would be possible, but my start battery is 12V, my engine panel is 12V, my start motor is 12V, my alternator was 12V and when replacing the alternator with a shiny new one, I don’t really see the need to change to 24V.

I don’t charge the house battery with the alternator. It never did, it used the two additional alternators to charge the house bank and I removed all that without putting anything back. The new alternator replaced the standard OEM alternator.

Also, I just bought my second LFP bank (2x LiTime 24V 200A so 10.24kWh like my other bank) and these are stupid drop-in batteries without any access to the BMS. So no warning signal output to stop the regulator. I can simply drop them in anyway because my alternator is not affected by HVC at all

[Dockhead]

Originally Posted by s/v Jedi

Let me add to this the two scenarios that I use alternator charging:

1. A backup for a backup. Very unlikely that both my solar and my genset stop working but alas here’s another charge source, why not.

2. In case I am underway and it is night and there absolutely is no wind at all and I have a schedule. This is hard to believe but I may even get antsy without a schedule and want progress during the dead calm night so I use the diesel. For this case I like to have plenty power because when this happens we tend to make heavy use of the galley, entertainment systems etc.

Both of these are very unlikely because I simply don’t leave when there’s no wind. But I can remember a couple of cases in the past 20 years of sailing Jedi so it does happen. Also, we are lucky with our boat because even in only 7 knots wind on the beam we can sail 4 knots STW on working sails and I can tolerate that

Another good use for heavy duty alternator charging, even on boats with other sources of power, is making electrical power as a byproduct of propulsion.

If you're motoring, the power is on. As you say, motoring in a dead calm is low workload in the cockpit and time to cook, do laundry, use power. Down in the trade winds maybe you have the luxury of just waiting for wind, but in most parts of the world, even up in my latitudes, you get a fair amount of dead calm. I motored all the way from Iceland to Greenland once -- up there it's either dead calm or F7 or F8, and believe me, you prefer motoring in dead calm to sailing in F8 with ice in the water.

If your batteries are down after a long passage under sail, you get some charge in them from motoring into the harbour or anchoring or whatever.

I guess if you have a giant solar installation which keeps the batteries up always and no matter what, you might not care about this. But for many use cases, this is a very good thing.

I don't have solar at all on this boat (trying to avoid windage), so the heavy duty alternator does the above plus backs up the generator. My generator is extremely reliable but I have been unable to start it a few times over the years for whatever reason and I was always glad to have the heavy duty alt.

Even on a boat with a lot of solar, heavy duty alternator is cheap backup. I don't think you can have too many redundant sources of electrical power; a significant percentage of the really bad long ocean passage stories I know are related to loss of electrical power, which can be dangerous, besides very uncomfortable, if you depend on an electrical-powered desalinator for fresh water. Three sources of electrical power is not excessive, in my opinion, in such a case.

Thread drift, but Nick, when do you expect your Yanmar to "give up the ghost"? How many hours do you have on it?

[Mozz]

Sorry this has nothign to do with subject . just joined and cant work out how to ask a question, not easy!!

[sailingharry]

Originally Posted by s/v Jedi

You leave out crucial information. What make and model are your alternators? A Powerline 120 (factory V-belt) and a Powerline 140 (custom serpentine) Do your Balmar regulators have temperature sensors on the alternator (as well as on the batteries) Both alternators are temp sensed. One regulator has battery temp sense (came with boat), but the second regulator is not -- with a max charge rate of about .25C, I'm not terribly worried about battery temp.

Do you run enough RPM’s to get full alternator output?
If you increase RPM’s more, does the output go up? I do not get full output, as I can't reach the top of the alternator RPM curve. Even at cruising RPM, about 80% of red line, I can see an increase in output when I go to 100%. Engine pulleys are such a limiting factor.
Did you set limiting parameters in the Balmar configuration, like for example “belt saver”? No limiting parameters in the Balmar. I don't see much value in arbitrary limits. When the alts are cold, I want every bit I can get (getting my AGM's to full is such a challenge that I don't want to make it harder by charging slower). Belt manager is about managing the BELT (and can be helpful on a small engine for HP management). Temp sensor is about managing alternator health. Note, with my 4JH2E, I have about 55 hp to play with so I'm not terribly worried about sending 10hp to the alternators.

How much amps and at which voltage goes into your AGM batteries during bulk charge. Ideally you have a graph for both voltage and amperage over a time X-axis. A graph would be a good idea. I should do that. I don't get to acceptance voltage until about 70-80% SOC, so until then the regulator is "WOT" (quoted because the alternator drops in capacity when warm, and the regulator drops excitement when hot). So, from morning (often as low as 50%) until 80% SOC (about 200Ah or more), I am sending 100% of what the system can produce.

If, during bulk phase the amperage goes down at all, then this is caused by the thermal design of the alternator. Exactly my point

So, more detail above. My point, which the above only reinforces, is that with a robust AGM bank and normal alternators (or even above normal, as I have), many cruisers already run the alternator at the limit for extensive run times. If I still had the single 120A alternator that the boat came with, I would be at full managed output for over 2 hours. An LFP may increase those WOT run times, but an AGM is already taxing the alternator heavily. The idea that installing an LFP suddenly whacks the crap out of the alternator is overstating the problem. If your alternator can already safely handle charging your AGM (which requires at a minimum an external regulator with temp sensing), then it is already able to handle LFP. If it can't handle LFP... well, it's already been cooked by the AGM. If installing LFP means I should take my 260A of alternator output and send it through a 20, 50, 100, or even 150A of DC-DC conversion, I don't understand why I don't need to do that this winter on my AGM battery.


I also really don't get an "LFP aware" regulator. A regulator knows precisely one thing -- volts. Well, most can "infer" output by analyzing excitation current, but it can't tell the difference between a charging load and a consumption load, and it doesn't know anything about alternator capacity (rated and real) or battery capacity/chemistry. An LFP charge profile is, at least fundamentally, simpler than LA. No bulk. No "other bulk" (Balmar has 2 different bulk stages). No acceptance. No float. No Equalization. It's one voltage setting, until it is full and then it turns off. This could be done with a rather "dumb" regulator, one that has a very accurate target voltage and alternator temp sense, with an "on/off" sensor wire to the BMS. Charge to target voltage, then turn off. Not anywhere near as complicated as LA.

[sailingharry]

Originally Posted by Dockhead

If your batteries are down after a long passage under sail, you get some charge in them from motoring into the harbour or anchoring or whatever.

This is perhaps the biggest argument for the biggest alternator you can fit with no limitations on the route to the battery. Those who sail the most, or are at anchor for long times, are heavily reliant on solar. When they turn on the engine, be it for the 30 minute trip to the anchorage or for a morning "boost" before the sun comes up, want that short run to be productive. Throttling even a wimpy alternator to a fraction of its capacity because "nowadays, I am mostly solar" is counter productive. If you motor hours on end, it really doesn't matter -- a 50A DC-DC can fully charge a depleted 400Ah LFP in an 8 hour motor trip. But if you have (as I do) 260A of alternator, in a short 15 minute engine run I can cram 70Ah into the battery and the alternators won't have begun to throttle back on temperature.

[Nicholson58]

Originally Posted by bgallinger

I have used a 100 amp Balmar alternator with a Balmar MC-614 external regulator to charge my batteries (3x Lithium house batteries and 1 x AGM engine start) for several years now without a DC-DC charger. I always charge the batteries to 100%. I also fitted a Balmar Transient Spike Protector on the alternator.

The spike protector is highly recommended.

We are 24 volts, LiFePo 630 AH house. I use Balmar 624 external charge controllers. My alternator is originally for light trucks and not capable of continuous full load output so the Balmar regulates to 50%. This works well while motor sailing with more power to the prop, cooler running of the alternator. I don’t consider the maim engine as a primary charging source. Use the engine to go. We rely on solar for 90% and run the generator once, twice per week. More solar to be added.

[s/v Jedi]

Yes, right. When you put alternator temperature control into the picture, it doesn’t matter anymore. This is what I have been writing all this time. The people who are burning up their alternators don’t have that and very few standard alternators come with external Balmar regulators

Still, this doesn’t cover the 2nd requirement which is a controlled shutdown before a HVC occurs, which is the 2nd requirement before charging a LFP house battery with the alternator.

Thise spike protectors are -not- a replacement for this. They are an additional protection measure, like a fire extinguisher is… you don’t start fires because you have an extinguisher… you do everything to prevent the fire and have the extinguisher as insurance policy. These spike protectors/surge suppressors are the insurance policy.

[mcon12000]

Originally Posted by s/v Jedi

Yes, right. When you put alternator temperature control into the picture, it doesn’t matter anymore. This is what I have been writing all this time. The people who are burning up their alternators don’t have that and very few standard alternators come with external Balmar regulators

Still, this doesn’t cover the 2nd requirement which is a controlled shutdown before a HVC occurs, which is the 2nd requirement before charging a LFP house battery with the alternator.

Thise spike protectors are -not- a replacement for this. They are an additional protection measure, like a fire extinguisher is… you don’t start fires because you have an extinguisher… you do everything to prevent the fire and have the extinguisher as insurance policy. These spike protectors/surge suppressors are the insurance policy.

👍

ABYC guy here and this is a great summery of why a DC charger might be a better choice for many folks. Lots of people add a Balmar setup (I have one love it) and think alright let’s charge the lithium house bank. Might work great for years but one BMS disconnect and say goodbye to some cash. The risk reward is debatable and my solution was to add two Victron 50amp Buck boosts (12v alternator w 24v house bank) this provided me redundancy and the fewest devices to address the problem. Price is close to three three 30amp DC chargers especially when you consider the additional wiring bus bars and time.

I have three DC to DC chargers in my system and they are invaluable. Two 24/12 service all my 12v loads and the gel battery that serves as boat ups and one 12/12 that keeps the start battery fully charged.

I’m in the group that considers the alternator the least important charging source. Not saying I don’t consider it important but my goal is to sit at anchor for weeks only running the engine for reasons like moving the boat.

[sailorboy1]

Be motoring for 2 hours. Alternator charging directly to 400 ah lfp house bank. 100a alternator putting out about 70a due to belt manager, alternator got to 90C, charged to 14v then did 12 minute before dropping to float. According to battery monitor got to 99.5% charge. Solar will do load rest of trip.

This stuff is so much easier than made out to be.

[s/v Jedi]

So let me repeat a tip for those who charge LFP from the alternator, who have a temperature sensor on the alternator and a spike/surge suppressor that hopefully protects the alternator diodes:

If you have access to the battery cells or if you use 12V batteries in series to create 24V or 48V then you can easily create a controlled shutdown of the alternator without touching a BMS.

For this you need a Victron Smart BMV-712 battery monitor. The shunt that comes with it has two inputs: battery positive and AUX. Battery positive measures battery voltage as well as powers the monitor and you connect AUX to the terminal that has half your battery voltage, i.e. the positive terminal of the 2nd cell in a 12V battery, or the battery terminal that shows 12V in a 24V system etc.
Now you configure the BMV for battery midpoint monitoring and to raise an alarm when balance is suspect. Also, to trigger it’s internal relay on that midpoint monitoring alarm. You can probably add a high voltage alarm to that as well.

On the back of the BMV display module you have the contacts of this relay. With those you can enable/disable the regulator. If your regulator doesn’t have a feature for this you can simply switch it off. You can even interrupt the blue field wire that runs to the alternator. Note that you probably need a bigger relay in between when you don’t have a remote enable/disable.

You don’t need a $1000 BMS to do this and many already have that battery monitor installed and just don’t use it’s features

[Pete7]

Originally Posted by Dockhead

P.S. As I think about this, it seems to me that this situation would actually be WORSE with a DC-DC charger, as that will pull a load even when the voltage is pulled down by heavy DC equipment, because it boosts the voltage to whatever is needed for charging. In my case, the batteries weren't drawing any current, because they won't when the voltage is below whatever is needed at that moment for charging. I guess this can be solved by properly programming the DC-DC charger, to stop charging when system voltage is below x.

My Orion Smart charger has a low voltage "lock out" which is user selectable. So, if the Orion is charging and something draws down the engine start battery below the cut off, the Victron shuts down until the voltage rises again.

Also Sterling recommend a maximum of alternator to DC>DC charger ratio of 60% which I guess limits short term high current draw from say a bow thruster. Several minutes of windlass might be pushing it.

However, we haven't found running a 30A charger off a 100A alternator a problem. If you can keep the charger cool and that is a separate problem, Victron quote the output as 430w at 25c.

That will do for us without stressing anything out like the alternator or belt.

Originally Posted by MWGDVC

My point to all of this, is we may be reaching the limit of easily bolted on electrical power solutions for the engines currently utilized.

Perhaps the solution then is moving the belt to run off a hydraulic gearbox as in the Beta hybrid solution already mentioned. 5-9kVA quoted in their sales blurb. Big bucks though.

[sailingharry]

Originally Posted by s/v Jedi

Still, this doesn’t cover the 2nd requirement which is a controlled shutdown before a HVC occurs, which is the 2nd requirement before charging a LFP house battery with the alternator.

Yes, I believe that an external driver to shut the regulator off well before a HVC is critical (and then eliminates the need for "managing" a disconnect, either by an in-line LA or a DC-DC or whatever -- even a zap-stop is only "extra insurance"). I used to believe that this also drove a requirement for isolated charge/discharge busses, but you (I think it was you) convinced me a while back that a single bus with suitable pre-event controls of loads and charging sources would essentially eliminate the risk of an actual disconnect, and make the need for separate busses all but moot.


A single pre-alarm for the HVC would kill the alternator, the solar, and the inverter/charger, precluding an HVC. A single pre-alarm for a LVC would kill the inverter, which is the single biggest continuous load. The inverter and the fridge both kill themselves on low voltage anyway, leaving very little in the way of loads that could drive the battery all the way to an actual low voltage disconnect.