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menzies

menzies

Guru
Joined
May 11, 2014
Messages
7,233
Location
USA
Vessel Name
SONAS
Vessel Make
Grand Alaskan 53
I have a house bank of 12 glass mat batteries. I have two 8D start batteries. All are less than two years old.

I have a Blue Seas ACR. This senses a charge going to any battery from any source and automatically combines the banks for charging. Once that charging source stops (ACR recognizes as drop in battery charge) it stops combining.

I started noticing last season that my start batteries, (as seen at the helm voltage meters) would start off really healthy but on a long day's run (say 8-10 hours) it starts to drop below the 24 volts and into the red. It is happening again now on this Bahamas trip, with some long days again.

To ensure all systems are supported I crank the genset until the end of my run

So I decided to sit staring at the ACR and work through what could be happening here. I have ended up with this theory that I would like you bounce off you and then a question.

I run the genset in the evening and charge everything up. The ACR relays since it senses a charge source. Next morning I start the engines and off we go. Now there is a charging source from the alternators. So the ACR relays again. And not only keeps the starts charged but also the large house bank - which the 4K inverter is using to run a house which currently included a large domestic fridge freezer AND a chest freezer. I don't know the ampage of my alternators but my theory is that they can't manage that load and do the engine starts are getting drawn down.

Thoughts on that? Anything else.

The question: I am thinking of turning off this relay and starting the genset. Then seeing if both banks are being charged without the ACR, i.e directly by the genset. Then leaving it off allowing the altenators to manage only the start batteries. And using the genset daily as I already do to charge the house. Thoughts on this?
 
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If you are cruising with main engines and no gennie, and alts are being over run by load, they will get HOT trying to pick up the load. Go in ER and see how hot they are with engines on. If any are cold, sounds like a pooped alt or ACR is somehow not combining.

Redneck troubleshooting!

Can also put a voltmeter on alt output lugs and see what it reads, should be about 28V. If alt is cold and only reading 25 or less, it is not working.
 
If you're going to check alternator temperatures (which is a good idea), a laser light temperature gun as opposed to your hand, is a much safer way to go.

Ted
 
Ski in NC said:
If you are cruising with main engines and no gennie, and alts are being over run by load, they will get HOT trying to pick up the load. Go in ER and see how hot they are with engines on. If any are cold, sounds like a pooped alt or ACR is somehow not combining.

Redneck troubleshooting!

Can also put a voltmeter on alt output lugs and see what it reads, should be about 28V. If alt is cold and only reading 25 or less, it is not working.
Click to expand...

Will the alternators throw 24+ in idle?
 
O C Diver said:
If you're going to check alternator temperatures (which is a good idea), a laser light temperature gun as opposed to your hand, is a much safer way to go.

Ted
Click to expand...
I have a gun, and can see the alternators from one of the ER access doors. Just not sure if doing so at idle will tell me much.
 
menzies said:
I have a house bank of 12 glass mat batteries. I have two 8D start batteries. All are less than two years old.

I have a Blue Seas ACR. This senses a charge going to any battery from any source and automatically combines the banks for charging. Once that charging source stops (ACR recognizes as drop in battery charge) it stops combining.

I started noticing last season that my start batteries, (as seen at the helm voltage meters) would start off really healthy but on a long day's run (say 8-10 hours) it starts to drop below the 24 volts and into the red. It is happening again now on this Bahamas trip, with some long days again.

To ensure all systems are supported I crank the genset until the end of my run

So I decided to sit staring at the ACR and work through what could be happening here. I have ended up with this theory that I would like you bounce off you and then a question.

I run the genset in the evening and charge everything up. The ACR relays since it senses a charge source. Next morning I start the engines and off we go. Now there is a charging source from the alternators. So the ACR relays again. And not only keeps the starts charged but also the large house bank - which the 4K inverter is using to run a house which currently included a large domestic fridge freezer AND a chest freezer. I don't know the ampage of my alternators but my theory is that they can't manage that load and do the engine starts are getting drawn down.

Thoughts on that? Anything else.

The question: I am thinking of turning off this relay and starting the genset. Then seeing if both banks are being charged without the ACR, i.e directly by the genset. Then leaving it off allowing the altenators to manage only the start batteries. And using the genset daily as I already do to charge the house. Thoughts on this?
Click to expand...


Menzies, it might be helpful if you could draw us a picture -- also helpful to know which ACR you have...

https://www.bluesea.com/products/category/35/Automatic_Charging_Relays

I think you are on the right track overall. Your alternator(s) output is not sufficient to run your house/inverter loads throughout a long day.

Do the voltage levels for your "house" battery bank track with what you are seeing for your engine batteries?

Re: "I have a house bank of 12 glass mat batteries. I have two 8D start batteries. "


Wow... the house bank is 12 batteries? What size are these? Again, a picture will help.

I am also wondering if your ACR is sized correctly for the load.

By the way, Blue Sea Systems has some of the smartest people on the planet. I have called them in on many projects (professional and personal) and they always blow me away...

re: "I am thinking of turning off this relay and starting the genset. Then seeing if both banks are being charged without the ACR, i.e directly by the genset. Then leaving it off allowing the altenators to manage only the start batteries. And using the genset daily as I already do to charge the house. Thoughts on this?"

Worth a try if it is easy to do, but I would really want to know more if it were me. By any chance, do you have a DC Clamp Ammeter? The AC ones are simple and cheap, but DC is another story. These things work on the same principle as your autopilot gyro-compass (magnetic fluxgate sensor), and they used to cost a fortune.

Now you can get one for around $100...and this one is bloody EXCELLENT.

https://www.amazon.com/gp/product/B00ICSW4QK

With the ability to measure up to 1000A DC, absolutely a lifesaver if you have trouble cranking. Don't leave port without one... ;-)
 

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menzies said:
I have a gun, and can see the alternators from one of the ER access doors. Just not sure if doing so at idle will tell me much.
Click to expand...
Leave the transmissions in neutral and run the RPM up.

Ted
 
I believe the ACR only joins the two banks together when the voltage goes above 27.2v for 30 seconds (https://www.bluesea.com/products/7610/SI-ACR_Automatic_Charging_Relay_-_12_24V_DC_120A). It opens when the voltage drops below 25.5v for 30 seconds.

It seems like the alternator output is connected to the house bank and the draw on the house bank/alternator is causing the voltage to drop below the switching threshold of the ACR. While you are underway, the start battery is being drawn down by the electrical demands of the engine. With the ACR off, the inverter wouldn't affect your start batteries. I would start by mapping out your charging system. It sounds like you have two alternators providing charge. Are their charges combined to charge the house bank? A 4000 watt inverter at 24v would be drawing roughly 170 amps. It is unlikely the inverter is drawing that much current so a close examination of the charging system including the inverter/charger is needed, and that should start with a drawing.

Tom
 
I would start by verifying that both alternators are outputting. Also seems like you may be missing a part somewhere. Two alternators on one start bank that latches to a house bank or vice/versa? Usually two alternators would employ an isolator which is not ideal since it will drop the alternator outputs down slightly but typical of most installations.

Easy enough to check the alternators by running the engines separately and watching what the voltage does. Also check the temperatures of all your batteries. You could have a bad one. Point and shoot IR will locate it or just run your hand across them and look for one or more with warm spots indicative of internal soft shorts. A failed/failing battery will cause mischief.

Could be more than one thing...
 
Tom, I have a full set of wiring schematics from the build. I will have to see if the ACR is on there or a later addition.

You say the inverter wouldn't impact the starts if the ACR is off, but right now it is always on. That is my question, what would be the impact if I just turned it off.
 
Singular or plural?

menzies said:
This one.

https://www.bluesea.com/products/7621/ML-ACR_Automatic_Charging_Relay_-_24V_DC_500A

Batteries are 8AGC2, golf cart.

And yes, both banks track the same.

Wondering if the relay is designed to manage the pull from the alternator so keeping it from getting hot?
Click to expand...


Above you said alternators, but now it's 'alternator' Is this a single engine setup?


If both battery banks are tracking the same, then it seems to me you are pulling more juice out of the batteries than your alternator(s) are putting back. What kind of RPMs are you turning on one of these long days?

Remember, an alternator rated at xxx amps is probably not putting out xxx amps until you get your RPM's up...


Does your inverter setup tell you how much juice it is pulling? Are you running monster loads (like the water heater) from your inverter throughout the day?
 
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Riverguy said:
One alternator? Is this a single engine setup?


If both battery banks are tracking the same, then it seems to me you are pulling more juice out of the batteries than your alternator(s) are putting back. What kind of RPMs are you turning on one of these long days?


Remember, an 80A alternator is probably not putting out 80A until you get your RPM's up...
Click to expand...

Two engines, two Neville alternators. Running 1800.

I agree that there is more draw than they can handle, but how to turn off the house draw, and charge that with genset later.
 
bglad said:
I would start by verifying that both alternators are outputting. Also seems like you may be missing a part somewhere. Two alternators on one start bank that latches to a house bank or vice/versa? Usually two alternators would employ an isolator which is not ideal since it will drop the alternator outputs down slightly but typical of most installations.

Easy enough to check the alternators by running the engines separately and watching what the voltage does. Also check the temperatures of all your batteries. You could have a bad one. Point and shoot IR will locate it or just run your hand across them and look for one or more with warm spots indicative of internal soft shorts. A failed/failing battery will cause mischief.

Could be more than one thing...
Click to expand...

I am just about to turn off the ACR and start the genset to see if both banks are being charged. If not then I need to turn the ACR back on.

If they are being charged I will be able to see in the morning if the starts have retained the charge and only the house was drawn down. Then see if the alternators keep the starts green during my run tomorrow.

The "issue" with mapping everything out is that I am in the Islands Mon, and I am trying to get to a solution that works for now and solve it when I get back to home base!
 
AHAH! (I think!)

I just went to turn the ACR off and found out that it is a three way rocker switch. On/Auto/Off!

It was set to On. I have now set it to Auto instead of Off, so will see what impact that has.

I'm now wondering if the yard, at the start of last season, when they were replacing all of the house batteries, needed to turn off the ACR to do their work and then just put it to On when they had finished.

Now I don't know exactly how this ACR works (but will make it a point to find out) and what the difference from On to Auto means, but it could be that the relay was always closed and relaying!
 
menzies said:
Two engines, two Neville alternators. Running 1800.

I agree that there is more draw than they can handle, but how to turn off the house draw, and charge that with genset later.
Click to expand...


Ideally you want to be able to run all day off the alternators. Not sure which Neville's you have, but the standard models are 35A units at 24V. By 1800 RPM you should be at 30A each (roughly). 60A at 24V is 1.44kVA which (by the time it gets through your inverter and I-squared-R losses), you probably have 1,100 watts to play with, both AC and DC. It's easy to use that up with a single A/C unit, or a slow-cooker or what-not. Nav electronics these days are surprisingly juice-thirsty.


Slip that DC clamp ammeter around your alternator outputs (each, individually), add them together. Then use the same technique to see what is going into the inverter and finally into your main 24v DC bus. This will tell you how much your alternators are actually putting out, and where it is going...


Good luck...
 
Maybe I missed this, but are you combining a (presumably) 12V house bank with 24V starting batteries?
 
Mikala said:
Maybe I missed this, but are you combining a (presumably) 12V house bank with 24V starting batteries?
Click to expand...

Nope both banks are 24v.

And to your point, I seem to be combined, but don't want to be!
 
It sounds like you found your issue with the switch position. I was starting to wonder if it was one of the ML units with the switch installed, we had some similar issue a few years ago on one of our vessels here. IF that doesn't take care of it, I have an easy short-term solution for you that will get you back to civilization. Let us know.
 
So I put it on Auto and started the genset. The house 24v is charging perfectly. The engine starts are not.

So clearly I have now separated the starts from the charging system, which probably means separated from the house draw as well, which is what I want.

I will watch the starts for another hour or so and if they definitely are not charging I will turn the ACR back to On to get those starts fully charged. Then once I turn off the genset I will turn the ACR to Auto again which will separate the starts from the house for the night. I can confirm that in the am.

Then tomorrow as we run I will monitor the starts to see that they are being maintained by the alternators. If so then I have my solution, and can turn the ACR to On in the event that I do need to charge the starts or need a parrallel start.

Will update on this tomorrow evening after our run from Georgetown to Long Island.
 
There are a couple different ways to wire the ML series ACR, and it will perform differently depending on how it is wired. On the Blue Sea site it show a .jpg for the standard wiring diagram, but if you look in the .pdf instructions it shows the different ways it can be wired for different functions. If it still is not performing the way you think it should be, you may have to look further into how it was wired.
 
It kind of sounds like the ACR is not working. In the on position both banks are paralleled. In the auto position, the voltage must be above 27.2VDC on the side where the charge is applied to parallel the banks. When you are charging, check the voltage on the both sides of the ACR. When it's switched on the voltage should be the same. In the auto position it will only be the same if the voltage reaches 27.2VDC. The On position is kind comparable to a separate battery switch where you can manually parallel the banks when the ACR fails.
 
Ok, anchored in Thompson Harbour, Long Island and can now report that the issue is indeed resolved.

We ran the genset last night with the ACR set to On. That charged up both banks. We turned the genset off before bunking down, and I turned the ACR to Auto. Woke up this morning with the house bank drawn down as expected, and the starts holding where they were left last night - so properly isolated!

Ran at cruise the four and a half hours to Long, still with the ACR set to Auto, and the alternators kept the starts happily in the green with no loss.

So now I understand the On and Auto settings (will use the On when the boat is sitting at the dock and not being run for a while to keep both banks up, but then switch to Auto when off cruising). Simply put the On is putting the banks in parrallel permanently.

Now the question I need to answer (but can wait until I am at home dock) is what does Off do?
 
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That is great news! Keep on cruising. Seems like AUTO should be the go to setting at all times but I would stick with what is working right now:) Pretty sure OFF means no latching at all.
 
You should be able to keep the ACR in "Auto" while on shore power. Should be no need to go to "On" unless it fails and you need to parallel the batteries.
 
tpbrady said:
You should be able to keep the ACR in "Auto" while on shore power. Should be no need to go to "On" unless it fails and you need to parallel the batteries.
Click to expand...

I agree, but will need to monitor that Auto kicks in if the starts fall below a certain charge.
 
The Blue Seas ACRs have an output for a "combined" LED. I have LEDs installed at the electrical panel wired to my two ACRs so I can clearly see when the ACRs are closed and when they aren't. I realized that "out of sight out of mind" is a bad thing with these since their function is so important.


Ken
 
kchace said:
The Blue Seas ACRs have an output for a "combined" LED. I have LEDs installed at the electrical panel wired to my two ACRs so I can clearly see when the ACRs are closed and when they aren't. I realized that "out of sight out of mind" is a bad thing with these since their function is so important.


Ken
Click to expand...

Great idea. I may add that to the end of year yard list.

So what I saw last night when running the gen was that only the house was getting charged, and not the starts. after a couple of hours the starts were getting charged as well. So clearly on Auto, once the ACR senses that the house has reached a charge level that the switch is set for (just over 25 volts I believe), it then shares the charge with the other bank. Which is fine.

The more important thing was, leaving the gen off during the night, the house was drawn down in the morning as it should be, but the starts were still sitting fully charged. So They get the spare charge when it is available, but are isolated on the draw - just what I want!
 
I have a similar set up.

The PO had replaced the batteries because they would not hold a charge.

Trouble shooting the system I found the ACR had failed open, with no fault indication.

It was replaced under warranty and I now have a spare.

The current threshold for the relay is roughly the non inrush draw of the 8D 12v battery. So my guess is it's life is about a year.

A better design would be to charge the largest batteries of the charger, and the genset battery off the relay.

Genset alt can charge it's own battery if the ACR drops out.

I am making that change later this summer.
 
Are you suggesting that the ACR life could be only 12 months?
 
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