Any alternator experts?

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fallguy1000
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Any alternator experts?

Post by fallguy1000 »

So, I have two Yamaha VF90 with 33a alternators.

And I added Victron dc-dc smarter chargers 12/24/15 to charge my house bank.

So, they would theoretically charge at 30A until they hit absorption. 30A@12vdc=15A@24vdc

My battery bank is AGM with 184Ah, so a 50% low system requires 90Ah to fill or so. Running both engines would deliver 30A, so in 3 hours, my batteries are fully charged.

The problem, I am told, is if I try to pull a continuous 30A@12vdc from each engine; the alternators are only designed to flow a charge back to and top off the start battery; they are not designed to run for 3 hours and if I try; they will fry. They are a grand each to replace.

Now, I have been onboard houseboats and they all have you run the boat for like two hours in the morning to bring up the house, but they must have some way to keep the alternators from roasting, or perhaps they are running all 12v and so not pulling so much current as the converter would?

So, I can turn off the charger with my phone, so I could run it a minute and off for three, but that and fishing or running the boat sounds like overloaded captain.

So, the alternative is a Victron buck boost 25A charger which allows me to set the current rate. I already have the other systems installed and they cost about $350 for both. The buck boost is like $400 each..

Any expertise on 12-24v charging?

Been told it works with a big 120A alternator, but not small ob.
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Jaysen
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Re: Any alternator experts?

Post by Jaysen »

I've never seen 24v charging from outboards. Not even gas motors. Always an inboard diesel. And then the diesel has been 24 volt (big cats) and the boats ran separate generators for house power. Doesn't mean it isn't done elsewhere, I've just never seen it.

I think your answer is the buck. You can't swap out voltage regulators since your motors need the 12v. You can't put in "big boy" alternators on outboards like you can in inboard.

I kind of call BS to the "burn up the alternator" bit unless they sell a motor version with a beefed up alternator (aka "sailpro"). If they have such a version see if you can swap alternators.
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TomW1
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Re: Any alternator experts?

Post by TomW1 »

fallguy have you looked into ACR's from Blue Seas. They will stop the charging to the battery when they are fully charged, after that I don't know much how they work. They have both 12 and 24V ones. You can contact them and see if they can do a system for you with what you already have.

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jonnymac
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Re: Any alternator experts?

Post by jonnymac »

I personally wouldn’t worry about it. Its going to be hard to predict exactly what your real life usage is going to be. the enemy here is heat generation in the alternators due to current flow, i can’t believe that a modern alternator couldn’t handle rated load. i believe with victron, they have an open source communication protocol where you could use temp sensors to turn the charging on and off automatically.

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Re: Any alternator experts?

Post by jonnymac »

what is your model of charger? I can help on technical solution. also is there a label plate on alternator, post a picture if there is.

fallguy1000
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Re: Any alternator experts?

Post by fallguy1000 »

The charger is Victron Orion TR Smart 12/24-15. The datasheet is all 4 products, mind is 2nd column.

https://www.victronenergy.com/upload/do ... 00W-EN.pdf

It is designed to convert 12v to 24 to send to my 24v house bank at up to 15amps. This means it will pull 30A at 12v which is basically the max alternator output.

Consider a deeply discharged house that is say half depleted. I have 4xagm 92 hour batteries combined to 24v. So they are 184AH total. I may add/change the bank to lithium iron phosphate someday.

I have been warned against cooking the alternator by several people including my old school alternator repairman used for 13 years.

Here is the Victron thread where I asked about current limiting.

https://community.victronenergy.com/que ... neral.html

I will get rating plate pic in an hour.

The pic was before all wiring..
A62EEBD8-8A8C-4059-AEAE-95932E5370FD.jpeg
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OrangeQuest
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Re: Any alternator experts?

Post by OrangeQuest »

I don't know much about the charging systems of outboards and most my knowledge is in the automotive type systems but I can't resist adding my two cents worth!

Let's talk about how a charging system works. With your motor running, the voltage regulator looks at the battery voltage, let's say it is less than 12 volts. The voltage regulator will start turning on alt output to reach around 14 volts. The exact amounts are not important for this example. To see 14 volts, the alt puts out high amps till the voltage starts to go up and then the regulator backs that output off to bring it back down to 14 volts. That is how the charging system works to recharge a battery after starting a motor.

Now, you turn a load on like the A/C (10 amps), voltage drops at the regulator, so the regulator puts out enough current to make up for that load and maintain 14 volts. No matter what, as long as the motor is running and the charging system works correctly, that is what happens.

If your house demand for power is greater than what the two motor charging systems can put out, then they will put out their max till the load drops or they burn up. But the way I am reading your spec sheet of the device you are using; it looks like it regulates the max demand for your charging system is 15 amps and the max it will go to is 24 amps for a short time (10 sec)? That seems a good safety margin for your motor charging systems. I would put something like an ACR or battery isolator between the device and the starting battery to keep the starting battery from being over charged. That way the starting battery gets charged back up first then all alt output goes to the house.
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fallguy1000
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Re: Any alternator experts?

Post by fallguy1000 »

OrangeQuest wrote: Tue Jul 12, 2022 9:58 am I don't know much about the charging systems of outboards and most my knowledge is in the automotive type systems but I can't resist adding my two cents worth!

Let's talk about how a charging system works. With your motor running, the voltage regulator looks at the battery voltage, let's say it is less than 12 volts. The voltage regulator will start turning on alt output to reach around 14 volts. The exact amounts are not important for this example. To see 14 volts, the alt puts out high amps till the voltage starts to go up and then the regulator backs that output off to bring it back down to 14 volts. That is how the charging system works to recharge a battery after starting a motor.

Now, you turn a load on like the A/C (10 amps), voltage drops at the regulator, so the regulator puts out enough current to make up for that load and maintain 14 volts. No matter what, as long as the motor is running and the charging system works correctly, that is what happens.

If your house demand for power is greater than what the two motor charging systems can put out, then they will put out their max till the load drops or they burn up. But the way I am reading your spec sheet of the device you are using; it looks like it regulates the max demand for your charging system is 15 amps and the max it will go to is 24 amps for a short time (10 sec)? That seems a good safety margin for your motor charging systems. I would put something like an ACR or battery isolator between the device and the starting battery to keep the starting battery from being over charged. That way the starting battery gets charged back up first then all alt output goes to the house.


The charging system 'sees' a voltage drop, typically from starting, and boosts the battery back. Because a low battery won't start the engine; this means ob alternators don't need to do much, generally.

The 15amp of the charger is the output side. There is no limit to the input side and nothing keeps the current in check. 15A@24v = 30A@12v. The charger is going to be pulling full power from the alternator and in theory both engines could be doing it. This brings up another problem.

The charge rate at C-10 for a 184AH bank is supposed to be 18A. So, the Orions can NEVER run at the same time, or the charge rate would be C-6 (184/30). btw, I also just learned this. I can software disable..so no need for switching. But software enable/disable/enable to keep the alternator cool is a terrible concept. Maybe okay at idle until you forget a disable cycle for ten minutes and fry the alternator. They are a grand each!
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fallguy1000
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Re: Any alternator experts?

Post by fallguy1000 »

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fallguy1000
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Re: Any alternator experts?

Post by fallguy1000 »

Any ideas?
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