Dual alternators, one regulator?

[EngineerRetired]

One more time....
Guys, I am not here to debate issues. I gave my best opinion based upon my background and education. I haven't looked but I'd bet a dollar the AYBC standards say the same thing I've been saying.

With that said, by all means, if you think it a good way to wire your boat then please go right ahead.

[tanglewood]

Originally Posted by EngineerRetired

One more time....
Guys, I am not here to debate issues. I gave my best opinion based upon my background and education. I haven't looked but I'd bet a dollar the AYBC standards say the same thing I've been saying.

With that said, by all means, if you think it a good way to wire your boat then please go right ahead.

I don't believe they do.


Also consider that there are other potential sources of ripple, in particular from loads. Inverters can create a lot of ripple, where "a lot" is 10s of mV. But people run chargers and inverters connected to the same battery system all the time.


For anyone new to this, you pose a good questions, but it's one that in practice is a non-issue.

[goboatingnow]

Originally Posted by EngineerRetired

One more time....
Guys, I am not here to debate issues. I gave my best opinion based upon my background and education. I haven't looked but I'd bet a dollar the AYBC standards say the same thing I've been saying.

With that said, by all means, if you think it a good way to wire your boat then please go right ahead.

Again ,your arrogance is astounding ,

[goboatingnow]

Originally Posted by tanglewood

I don't believe they do.


Also consider that there are other potential sources of ripple, in particular from loads. Inverters can create a lot of ripple, where "a lot" is 10s of mV. But people run chargers and inverters connected to the same battery system all the time.


For anyone new to this, you pose a good questions, but it's one that in practice is a non-issue.

He doesn’t pose a good question. , he doesn’t understand the basics of “ imperfect voltage sources “ at all nor the fundamental control
mechanisms behind a voltage controlled alternator.

Nor has he read the relevant ABYC standards.

[goboatingnow]

I’m hesitant to get into a technical debate with this because the person claiming ripple is a problem doesn’t fundamentally understand the basic of a voltage regulated charge source.

Let’s consider any two parallel but independent charge sources ( voltage controlled )connected to a battery

There are a couple of sceanarios

source A sees a voltage above its set point. the feedback loop will then adjust the voltage source to “ attempt “ to regulate to its voltage

Note “Attempt “. A imperfect source like an alternator , mains charger or solar controller can only do what’s possible. So the regulator will command less and less current in an attempt to lower the output voltage

Remember the charge source is not an active load ( it is what’s known as a 1-quadrant source ) it cannot actually reduce an external voltage all it can do is reduce its current to zero ,if the regulated voltage doesn’t fall , it can do no more.

This is what happens every time your charge your battery , eventually the battery voltage rises above the charge set point and the current falls to zero


Equally if the external voltage is lower then the charge source setting , all the regulator can do is command maximum current in an “ attempt “ to raise the external voltage , as its an imperfect source it has a limit to its power and the regulator will limit the output to within the design tolerances. If the voltage doesn’t rise according the alternator will simply continue ( under the control of ohms law ) put out current into the load . This is exactly what happens in the bulk charge phase of battery charging )

Hence “ ripple” does not cause charge sources to fight one another at all , as charging sources do not act as loads ( well 1 quadrant ones don’t )

[s/v Jedi]

Agree with the above, but let me add a potential problem:

During bulk charge all is great and every charge source is giving all it can. It is during the later part of the absorption phase that some sources can decide to finish while others continue and one may end up doing everything by itself. In case of two alternators on one engine, the sideways pull by the V-belts on the crankshaft cancel each other out but when only one alternator does the work, this effect is mostly cancelled and the crankshaft bearing gets more wear.

For lead acid this never really was a problem because at this stage of charging the current has tapered off to only a fraction of the initial charge but for lithium it can still be significant.

I have always used one regulator for two big alternators bolted to my engine. The boat came with a Lestec regulator that could do 15A field current and I replaced it with an Ample Power regulator that could do 15A as well. Never any problem.

Upon converting to lithium, I simply removed both of these alternators as charging is now done by solar. To regain some of the lost capacity, I replaced the oem alternator (yes I used to have three alternators total) with a Balmar 170A with temperature sensors mounted on the alternator as well as the AGM start battery and a nice serpentine belt system. Then I added smart DC-DC converters to take part of that output to charge lithium while powering during the night when solar is down.

With a catamaran I would take that same path so use two nice alternators with each a regulator that senses alternator temperature as well as agm start battery temperature, charging just the start batteries, then add dc-dc converters.

[goboatingnow]

Yes , as I mentioned , absorption mode can be an issue and as you say it tends to leave a “ lazy “ alternator. But equally for the majority of cases it doesn’t matter

[lvictorlucas]

[QUOTE=sailingharry;3434595]The answer is a resounding yes. I did the exact same thing on my boat, and before I did it I contacted Balmar." Glad to see a good answer so I did not have to explain it. There is a lot of mis information on any public form.

[maclysaght]

Thanks to those who have provided useful responses. I think I am going to go with the Balmar MC-612-Dual, along with battery and alternator temp sensors.

I still have one question: My current system allows me to "switch off" one, or both, alternators with a simple switch on my control panel. Is this still a good idea?

[goboatingnow]

You can use 1 regulator and two alternators provided the field current is sufficient, you can use two independent regulators, you can use sophisticate balancing regulators , The worlds your oyster

[RaymondR]

Originally Posted by s/v Jedi

Agree with the above, but let me add a potential problem:

During bulk charge all is great and every charge source is giving all it can. It is during the later part of the absorption phase that some sources can decide to finish while others continue and one may end up doing everything by itself. In case of two alternators on one engine, the sideways pull by the V-belts on the crankshaft cancel each other out but when only one alternator does the work, this effect is mostly cancelled and the crankshaft bearing gets more wear.

True but the single alternator still generating charge current is probably by this time lightly loaded and consequently the lateral load on the engine fairly low anyway.

For lead acid this never really was a problem because at this stage of charging the current has tapered off to only a fraction of the initial charge but for lithium it can still be significant.

So we now need the regulators to have an input for the state of charge of the lithiums and a second from the MFDs TTG on route in order to calculate alternator output so that the division of power draw on the engine between propulsion and battery charging is optimized.

I have always used one regulator for two big alternators bolted to my engine. The boat came with a Lestec regulator that could do 15A field current and I replaced it with an Ample Power regulator that could do 15A as well. Never any problem.

Upon converting to lithium, I simply removed both of these alternators as charging is now done by solar. To regain some of the lost capacity, I replaced the oem alternator (yes I used to have three alternators total) with a Balmar 170A with temperature sensors mounted on the alternator as well as the AGM start battery and a nice serpentine belt system. Then I added smart DC-DC converters to take part of that output to charge lithium while powering during the night when solar is down.

And thereby in one fell swoop doing away with the former reliability redundancy that dual alternators provide and introducing a huge lateral load to the engine?

With a catamaran I would take that same path so use two nice alternators with each a regulator that senses alternator temperature as well as agm start battery temperature, charging just the start batteries, then add dc-dc converters.

Or use two alternators with temperature sensing and rely on this function to prevent alternator burn out?

In the case of my gas engine driven, twin alternator, battery charger I don't care if one alternator is carrying more load than the other. I start her up and after about five minutes do an olfactory check (take a sniff downwind) for belt over heating, and do a touch test on each alternator for over heating.

[EngineerRetired]

Originally Posted by maclysaght

Thanks to those who have provided useful responses. I think I am going to go with the Balmar MC-612-Dual, along with battery and alternator temp sensors.

I still have one question: My current system allows me to "switch off" one, or both, alternators with a simple switch on my control panel. Is this still a good idea?

Absolutely a good idea. One use to consider. Lets say you have 125 amp alternators. Roughly you can figure about 1 H.P per 25 Amps so 5 H.P. at full alternator output. Now assume you have a depleted battery bank and you fire your engine(s). The alternators are going to go full tilt to bulk charge that battery bank, on a cold engine. Not the best thing in the world for the engine, belts, etc.


Also think about this, your engine is maybe in the 30 HP range??? You want to maneuver out of the slip / marina at what, 600 RPM. The alternators are going to eat all the power the engine is producing at those RPMs and you have very little left for propulsion.


Being able to shut off the field of the alternator, effectively shutting the alternator down, is a very handy and good option. Postpone charging until you are out of the marina, engine and belts warmed up and running at a working RPM.

[EngineerRetired]

Originally Posted by maclysaght

Thanks to those who have provided useful responses. I think I am going to go with the Balmar MC-612-Dual, along with battery and alternator temp sensors.

I still have one question: My current system allows me to "switch off" one, or both, alternators with a simple switch on my control panel. Is this still a good idea?

I know its a bit more costly but I recommend looking at a "smart" voltage regulator that uses a shunt to measure what is really going on. Especially if you are running a power inverter to make water, do laundry, etc. while your engines (and alternators) are running.


Here is an excellent article to help explain some of the issues of supplying power to loads while charging the battery bank. https://panbo.com/how-wakespeeds-ws5...-new-approach/

[Craig Staunton]

Check out

ZM5 - Smart alternator regulatorhttps://www.smartregulator.co.nz
Very inexpensive works great

[s/v Jedi]

Originally Posted by RaymondR

Or use two alternators with temperature sensing and rely on this function to prevent alternator burn out?

In the case of my gas engine driven, twin alternator, battery charger I don't care if one alternator is carrying more load than the other. I start her up and after about five minutes do an olfactory check (take a sniff downwind) for belt over heating, and do a touch test on each alternator for over heating.

No, you got that wrong. I did not have double alternators, I had triple alternators: one Hitachi 80A which was the oem one, on the same belt as the water pump and two Lestec Brute 225A alternators, each on it’s own belt. All three were replaced with a single 170A, mounted on a new serpentine belt system with new pulleys on the crankshaft and water pump as well. It works perfectly with a Balmar regulator with temperature sensors on both alternator and battery, as well as dual Victron smart dc-dc converters that detect when the Balmar starts spinning and take 60A of it’s output for charging the lithium battery.