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Old 28-09-2017, 10:55   #31
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Re: How to shutdown the alternator ?

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I wonder if it wouldn't be easier to switch off the ouput of the alt (B+). Of course I would need to stop the engine before. I guess I could live with it ...


I'm pretty sure if you ran the engine with the alt output disconnected you'd also fry the alternator.

Why not just put a rheostat on the field wire and dial it down until the output is in the 5 amps or less neighborhood? This allows you to keep the tach and run with no measurable load from the alternator.
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Old 28-09-2017, 12:45   #32
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Re: How to shutdown the alternator ?

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Ultracell batteries, 4x 250Ah. I know they are 100% SOC when they will not accept more than 10A @ float, that is 1% of capacity. That is somewhat confirmed by my BMV-700 showing close to 100% SOC. Of course the solar panels are willing to give (much) more at that time. To make sure this is really 100% I can also then start the boiler for a minute, the MPPTs go back to bulk, absorption, and then again to 10A in a few minutes.
100% SOC should be really determined by absorption voltage and tail current not float voltage & tail current. You're likely close but the voltage/pressure makes a difference in the accepted amperage.

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That is interesting ! I have set absorption voltage to 14.8V (victron mppt) which is somewhat in the middle of Ultracell recommandation (14.5 to 15V). Of course it would take much more time to recharge a battery 14.1V ... Not sure what to think here ...
I can't comment on those particular GEL batteries. The deep cycle GEL's I am used to installing to are made by either East Penn or Sonnenschein (Prevailers) (Sonnenschein licensed the technology to East Penn). These are the original GEL batteries and they last a very, very long time when properly charged.

Some of the Chinese makers are using a hybrid quasi GEL battery and those can have slightly higher voltages. Last time I checked I believe the UltraCell batteries are Chinese made (Taiwan if I am not mistaken) so I don't know what they call a GEL but if it charges at more than 14.2V or so it is not the same technology as the original Sonnenschein GEL technology. 14.8V to 15.0V would be death to a traditional GEL so I am guessing they are not the same type of "GEL".. The oldest GEL bank I have out there, still going, is 17 years old.

The boat I just left is heading for the Bahama's on Saturday. She's a 53' full time live aboard cruiser for 10 months per year. They only come back to New England for the summer, and still sail the boat, but it is just coastal stuff for those two months.. When cruising 95% of the time they are on the hook or on a mooring. The Gel batteries on-board charge at a max 14.2V (short duration) then drop to 14.1V and float at 13.7V. They are 10.5 years old and are leaving Maine for the Bahama's this weekend.

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You said I could switch off the iginition cable from the external reg, but then will I still get the RPM ?
No field means no stator pulse & no tach.

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And then you got me thinking, couldn't I just switch off the iginition from the Yanmar panel without any other changes / additional equipment ?
Killing the ignition won't always shut down an already excited alternator, this is why field needs to be cut.




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Poor alternators charging starter batteries is a broken design to me. I would like to fix it.
Millions upon millions of vehicles, boats, tractors, heavy equipment etc. charge start batteries when ever the engine is on every day.

I have lots of reserve/start batteries out there that have been charged via a combiner or direct feed alternator that are regularly exceeding 8-10+ years old and still doing their duty when called upon. Calendar aging often gets them first....

If you are concerned about the voltage simply place a diode isolator in the B+ path to the start battery and you now have continual float. Bump the game up a bit, with a switch, and choose between the diode path and no diode. Still seems like a lot of work to solve a problem that's not really a problem.
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Old 28-09-2017, 16:33   #33
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Re: How to shutdown the alternator ?

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I'm pretty sure if you ran the engine with the alt output disconnected you'd also fry the alternator.

........
Probably not, the problem occurs when you disconnect the alternator output while it is running (and delivering current).
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Old 29-09-2017, 03:01   #34
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Re: How to shutdown the alternator ?

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Millions upon millions of vehicles, boats, tractors, heavy equipment etc. charge start batteries when ever the engine is on every day.

I have lots of reserve/start batteries out there that have been charged via a combiner or direct feed alternator that are regularly exceeding 8-10+ years old and still doing their duty when called upon. Calendar aging often gets them first....
I live on the boat 365 days a year, 500h per engine per year, long crossing, often 20h+ in row with the engine(s). Do you really think I can get 10 years out of my stater batteries that are constantly at 14.4V ? (measured again this morning)

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Still seems like a lot of work to solve a problem that's not really a problem.
I am sorry I am failing at explaining why the design is broken and why it is stupid to waist fossil fuel when you have so much solar that would do the job in a better way (respectful to the batteries). Would you start a generator if you had 100A (@12V for a 1000Ah bat) about to come out of your solar panels ?? Thank you all anyway for your interest in the subject.
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Old 29-09-2017, 03:06   #35
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Re: How to shutdown the alternator ?

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Probably not, the problem occurs when you disconnect the alternator output while it is running (and delivering current).
seems I have to dig a little bit more on this subject... Anyone else ?
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Old 29-09-2017, 05:47   #36
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Re: How to shutdown the alternator ?

The only two safe ways to stop an alternator is to zero the field current or stop the rotation of the rotor.
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Old 29-09-2017, 05:59   #37
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Re: How to shutdown the alternator ?

What breaking strain of line are you using, and what lure ?
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Old 29-09-2017, 07:08   #38
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Re: How to shutdown the alternator ?

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Originally Posted by rom View Post
I live on the boat 365 days a year, 500h per engine per year, long crossing, often 20h+ in row with the engine(s). Do you really think I can get 10 years out of my stater batteries that are constantly at 14.4V ? (measured again this morning)
Again, if you are overly concerned simply create a switch that routes B+ through one side of a diode isolator (leave the other side empty) and you've now dropped 0.6V to a "float level". When you don't want the float level voltage switch back to no diode, but not while the alt is running.

Feeding a 99% - 100% SOC start battery is essentially zero work for the alternator and will be approx 0.05A to 0.5A at most. It is so close to OFF that it is not even worthy of consideration in regards to fossil fuel savings.


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I am sorry I am failing at explaining why the design is broken and why it is stupid to waist fossil fuel when you have so much solar that would do the job in a better way (respectful to the batteries). Would you start a generator if you had 100A (@12V for a 1000Ah bat) about to come out of your solar panels ?? Thank you all anyway for your interest in the subject.
You're simply not understanding that a full battery, as in the start battery, is taking so little current, that in terms of fossil fuel, it's not even going to be measurable in a realistically quantifiable manner.

If anyone, even using lab grade test equipment, could actually measure a fuel increase on a 50HP +/- marine diesel engine from an approx 3W to 6W load I would be quite surprised.

A spinning alternator, by the sheer nature of the design is wearing out brushes, slip rings, belts and bearings, even when OFF. Unless you physically remove the belt and stop its rotation this wear is already happening.. Sending a minuscule trickle current to a start battery is not realistically adding measurable wear to the alternator.

If you want to save fossil fuel & money avoid running your engine for 500 hours per year and simply sail more. My commercial lobstermen customers are doing in or around 1000 hours per year and they work long hard days. 500 hours per year, per engine, on a recreation boat, seems high especially when it is a sailboat the engines are rarely if ever used for charging. At an average of say 6 knots that means you are motoring for approx 3000 nm per year?

Rven a 20% increase in your sailing time or more aptly put a 20% reduction of your motoring time will pay for a lot of fuel or even a conversion to a better alternator and regulator. I seems like you are chasing the wrong issue on this one. More sailing, less motoring = less fossil fuel consumption.
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Old 29-09-2017, 07:42   #39
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Re: How to shutdown the alternator ?

@mainsail; let me rephrase: I made fuel economy because of this modification I made that allows me not to charge the house batterie with the alternators. Step two of the electrical system redesign, I want to get rid of the start batteries and start the engines with the house battery. Eveything you say is right, you are the expert, but I failed to properly explain you how my system works unfortunately, and this leads you to wrong assumptions and wrong solutions.

Anyway, from the responses I got here it seems I have no simple solution to stop the alt, and the best modification/simplification I can do on my system is to have one starter battery instead of two.
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Old 29-09-2017, 08:27   #40
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Re: How to shutdown the alternator ?

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@mainsail; let me rephrase: I made fuel economy because of this modification I made that allows me not to charge the house batterie with the alternators. Step two of the electrical system redesign, I want to get rid of the start batteries and start the engines with the house battery. Eveything you say is right, you are the expert, but I failed to properly explain you how my system works unfortunately, and this leads you to wrong assumptions and wrong solutions.

Anyway, from the responses I got here it seems I have no simple solution to stop the alt, and the best modification/simplification I can do on my system is to have one starter battery instead of two.
I don't get it either. Once full, batteries have such low rates of acceptance that the work any alternator has to do is negligible, regardless of how many batteries are connected to the AO or what the output voltage is (as long as it is within charge parameters, i.e., not too high to create damage and within battery manufacturer's specs).

Overcharging with Combiners or ACRs The MYTH:
Overcharging Batteries with a Combiner or ACR
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Old 29-09-2017, 09:27   #41
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Re: How to shutdown the alternator ?

He does not want to use the alternator to charge a not yet full bank. He wants to let the solar do that work. So most of you have misunderstood his reason for asking. He only wants to use the alternator when it suits him. The only ways I know are to stop rotor rotation or make the field current zero.
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Old 29-09-2017, 09:51   #42
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Re: How to shutdown the alternator ?

What you want can be done pretty easily if you have an externally regulated alternator. Just put a switch in the field wire. Its also possible to convert most internally regulated alternators to external regulation--find the brush connections, disconnect them from the internal regulator, and connect one to a field wire and one to ground.

If you want a cheap simple external regulator, NAPA sells them for $25.
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Old 29-09-2017, 11:35   #43
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Re: How to shutdown the alternator ?

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He does not want to use the alternator to charge a not yet full bank. He wants to let the solar do that work. So most of you have misunderstood his reason for asking. He only wants to use the alternator when it suits him. The only ways I know are to stop rotor rotation or make the field current zero.
Yes, Dan, I think we understand that. The point many of us have been making is that by doing that, which is a good thing, the alternator load is negligible in the total scheme of things, thus making shutting it off unnecessary and overly complicated.

We "regularly" get questions like "My tach stopped working when I first started up the boat - or was still connected to shorepower. Why?"

Because the bank was full and the regulator said to the alternator: no need to supply any current. Soon thereafter a load was applied and the alternator started working again and so did the tach.

This then, automatically answers his question, doesn't it? No need for anything fancier.
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Old 29-09-2017, 12:28   #44
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Re: How to shutdown the alternator ?

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He does not want to use the alternator to charge a not yet full bank. He wants to let the solar do that work. So most of you have misunderstood his reason for asking. He only wants to use the alternator when it suits him. The only ways I know are to stop rotor rotation or make the field current zero.
at last someone gets it ! thank you
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Old 29-09-2017, 12:46   #45
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Re: How to shutdown the alternator ?

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Yes, Dan, I think we understand that. The point many of us have been making is that by doing that, which is a good thing, the alternator load is negligible in the total scheme of things, thus making shutting it off unnecessary and overly complicated.
No Stu, you do not understand my problem. Like the other guy I should have said this is for "personal reasons" or for the sake of science...

But if you are interested let me try again: I want to convert a system with 2 start batteries + 1 house battery to a system with one house-does-it-all battery + 1 safety battery. By "safety" I mean a battery that is connected to the system through a 1/2/both/off switch which will hopefully always remain in position 1 (house). No need to explain how I keep this safety battery charge for now, let's admit it is not connected.

Now, in such a system the alternators are obviously directly connected the house battery, and they will charge it. Which I do not want because the solar panel can do it say 330 days a year. As I said I estimated the cost of the alternator charging the house instead of the solar panel in my case is somewhere between 200 to 400 EUR, plus wear and tear.

The second problem that arises is that those alternators will keep my house battery at 14.4V for 20+ hours in row quite often. Which I believe is not a good thing. External regulator you are now thinking ? yes, but I was looking for something simple.

Please don't tell me I should sail more, or I should buy a motor yacht. This is how it is. I was in the med summer 2016, I was in the carribean winter 2016/17, and I am in the med again, yes I the boat travels a lot, and it is actually much more than 3000 nm that I made with the engines over the last year.
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