Anyone use an ACR?

[Delfin]

Here is what my Blue Seas ACR does - quote from Blue Seas site:

Automatic Charging Relays - ML-ACRs
500 Amp magnetic latching (bi-stable) relay automatically combines batteries during charging and isolates batteries when discharging and when starting engine.

I'm not sure of the discharge current trigger point, but it is likely just a few amps such as the reefer draw. Hence the switching on/off I noted previously.

If the refer draws enough from the house bank to drop its voltage to the open voltage noted above, then the relay will open and isolate the batteries. When the voltage returns to the combine voltage, the circuit closes again and the batteries are combined. What sounds a bit odd in the situation you describe, is that a bank capable of recovering to the combine voltage after the refer goes off is drawn down enough when the refer/freezer goes on to open the circuit. Must be a heck of a draw coming from the refer...

 

[Cigatoo]

As they say, 100% false.



You have one on your boat that you've been using and observing for 12 years, John?

Here is what Blue Sea says an ACR does:

"ACRs or Automatic Charging Relays are automatic switches that close when the voltage on one of the batteries rises to a level (normally 13.2V to 13.7V) indicating the battery is connected to a charge source and is partially or fully charged. The switch then closes and shares the charging current with the other battery until the voltage drops to some lower level (normally 12.4 to 13.1 depending on model) and the switch opens. This prevents discharging both batteries when there is not enough current to charge both batteries."

They could also mention that this directs the full charge current to the primary battery bank. Until it is full or nearly so, the circuit between the two banks is open. Once the primary bank's voltage rises to the correct level, the circuit closes so the secondary bank is charged along with the primary.

Oddly enough, that is precisely how my, and I assume every other ACR on the planet, functions.

My interpretation is that the ACR will connect the 2nd battery once 13.5 volts is detected.....period. That would / could be the voltage coming from your charge source regardless of the actual SOC of the first battery. So you could have a house (1st) battery with a 50% charge but the ACR would connect the start (2nd) battery as soon as it detects 13.5 volts from the charge source. Ie the engine starts and the alternator kicks up to 13.5 volts. Therefore you will be charging both batteries just as though your switch was on “both” and absent the ACR.

 

[Delfin]

My interpretation is that the ACR will connect the 2nd battery once 13.5 volts is detected.....period. That would / could be the voltage coming from your charge source regardless of the actual SOC of the first battery. So you could have a house (1st) battery with a 50% charge but the ACR would connect the start (2nd) battery as soon as it detects 13.5 volts from the charge source. Ie the engine starts and the alternator kicks up to 13.5 volts. Therefore you will be charging both batteries just as though your switch was on “both” and absent the ACR.

The ACR senses the voltage at the primary bank. You can wire them up backwards so that the charge source goes to the starter bank, then you would likely get the behavior that John thinks is correct, but if you do it this way you defeat the entire purpose of the device.

On my system, what you describe never happened through hundreds of cycles. I now have LiFePO4 batteries, which are managed differently, but the AGM house bank I maintained for 11 years when, depleted and a charge source applied, would accept charging current for quite a long time before the circuit would close and the starter bank was also charged. That was the expected behavior and I never saw a "premature" combination of the banks, at least as far as I can recall.

 

[JDCAVE]

This unit https://www.bluesea.com/products/7620/ML-ACR_Automatic_Charging_Relay_-_12V_DC_500A

is the bees' knees, never have to replace it no matter how big an alt you put in, never fails, includes starter isolation even for dual engines, and offers self-jumpstarting from House at the press of a button

I have the 7622, which allows a manual override: manually combined, manually uncombined, automatically combined or uncombined.



This 3 switch panel is on the Pilothouse helm station

 

[psneeld]

I removed my Blue Seas ACR due to chatter, I could hook it up the other way, but thats not my style.

I should go a different route, but for novices, dont get sucked into simple advertising, it is a bit more complicated.

Again, a cruising electrical set up can be done many ways, but as one evolves and one makes compromise, simple additions dont always work.

Certainly not textbook unless you start all over and follow a different, well thought out with the new tech in mind....despite what some believe.

 

[FlyWright]

My Yandina combiner also operates as Delfin described, albeit at slightly different voltage points. Here's the Yandina manual that fully describes the operation in detail. They have some good schematics for various configurations.

http://www.yandina.com/acrobats/C150Data.pdf

Mine also has the option for a manual switch to manually open (always off) or close (always on) the combiner. With each engine's alternator directly connected to the house bank and start battery, I normally run with the combiner defeated/off. I have not connected the manual close feature since that defeats the purpose of having a combiner.

My single bank shore charger is connected to the house bank only. If the house bank needs a shore charge but the start battery is full as determined by my SOC aux batt voltage, I'll place the switch to off so the charge only goes to the house bank.

At the dock, the house is always charging on shore power. If the start battery is full and I expect to return to the boat in a week or two, I'll leave the start battery off the charger since it's just fine for that period with no parasite loads.

I also have two 1/A/2/O battery switches located just outside the ER door. On my boat, the combiner directs the start charge only. All loads are controlled by the battery switches which normally are not moved. If I need to combine bank loads or start with the house battery, I can move these switches for the temporary change. I only had to use them once when the boat came out of extended maintenance on the hard and the start battery was low.

PM me if you'd like a schematic of my electrical system to help with the layout of yours. I've posted it here several times in the past. Just can't put my finger on it right now.

john21ct, you seem to post regularly and authoritatively with book or google knowledge but with little or no experience with the systems in question. I've asked you publicly and privately about your experience 4-5 times and you have refused to answer. I've seen others ask and you have refused to answer. Do you own a boat? If I'm wrong, I apologize, but it seems those with actual experience in this are being told they are 100% wrong by someone with no stated experience. That's not right.

FYI, Delfin is one of our locally respected experts in many areas and I appreciate his insight and knowledge. If you want to tell us we're wrong, no problem...we're not always right, but you ought to have experience and credentials and know what you're talking about first.

 

[Delfin]

My Blue Sea is an older model that doesn't have built in switches, but provides for a three way switch to be added, which I did. It allows "No Combine", "Auto Combine" and "Manual Combine" via this switch. As I mentioned, Li batteries are a bit weird in their requirements and I prefer being a human voltage regulator so I use the switch as follows:

1. When underway and I want to charge the Li batteries, switch is on Auto Combine and the Li battery manager is "on", bringing the Li batteries into connection with the charging source.
2. When underway and I don't want to charge the Li batteries, switch is on Manual Combine, and the Li battery manager is off, disconnecting the Li batteries from charging, but allowing current to flow to the starter bank.
3. When at the dock, I want to store the Li batteries at 40 - 50% discharge for longevity, so the switch is on Manual Combine and the Li battery manager is off, diverting all charge current to the starter bank, which then supplies the 24v for the inverter and dc loads.
4. At anchor, the switch is on Auto Combine and the Li battery manager is on, allowing the Li bank to provide all required power for ship's systems.

Seems to work ok.....

 

[john61ct]

Oddly enough, that is precisely how my, and I assume every other ACR on the planet, functions.

Everything in your posts and others that follow are now correct, and in no way contradict what I wrote.

My point was simply that for every ACR/VSR/combiner, there is **no** detection of loads or current going on, everything is based on fixed **voltage** level setpoints only, sometimes with timers to prevent chatter.

Intention being: charge source present?

Yes, connect the two sides.
No, isolate them.

SoC or high-amp loads can affect voltage level, but that effect is incidental and unique to each install.

 

[Delfin]

Everything in your posts and others that follow are now correct, and in no way contradict what I wrote.

My point was simply that for every ACR/VSR/combiner, there is **no** detection of loads or current going on, everything is based on fixed **voltage** level setpoints only, sometimes with timers to prevent chatter.

Intention being: charge source present?

Yes, connect the two sides.
No, isolate them.

SoC or high-amp loads can affect voltage level, but that effect is incidental and unique to each install.

John, that is not exactly what you said. What you said was:

100% false.

When an ACR senses charging voltage it connects the two circuits.

When charge source stops it isolates them

The ACR does not connect the two circuits when it senses charging current. It connects them after the primary bank reaches the "combine voltage". The ACR does not isolate the batteries when the charge source stops. It isolates them when the "Open" voltage is reached.

If you were to wire up an ACR incorrectly by putting the reserve (starter bank) as the primary bank, then because it is likely to be at near full voltage most of the time you might get behavior that matches what you described, but that would only be because you wired it up wrong and are getting no benefit from the device as intended.

Not sure what you mean by "your posts are now correct." Since I didn't change anything in them, they were either always correct or always wrong. Seems like we agree they were always correct, and not 100% false as you stated.

 

[john61ct]

Yes we have been getting more precise in describing how they work.

Previous descriptions were ascribing more sophistication than warranted.

Someone would be misled thinking that the close setpoint is anywhere near House getting Full. With high-amp charge sources, the combining may happen within seconds or at most a few minutes, at the very beginning of a 5-7 hour charge cycle.

It is not any one element that determines circuit voltage, it is "negotiated" between the batts and charge source(s), and wire gauge, quality of connections may also play a role.

 

[Delfin]

Yes we have been getting more precise in describing how they work.

Previous descriptions were ascribing more sophistication than warranted.

Someone would be misled thinking that the close setpoint is anywhere near House getting Full. With high-amp charge sources, the combing may happen within seconds or at most a few minutes, at the very beginning of a 5-7 hour charge cycle.

I'll drop this now, but the above is simply not correct, at least in terms of how Blue Sea says their ACR works, or in my observations of how mine works, nor would I imagine how anyone else's observations of how theirs works.

 

[john61ct]

What I just stated has nothing to do with ACRs in general nor Blue Sea's.

That's just how charging lead batteries works, no matter the equipment involved, inherent in the chemistry and physics.

Bow out if you like, but if you want to learn more, feel free to ask specific questions and I'd be happy to explain what you see as discrepancies.

PS corrected "combing" to combining

 

[Delfin]

What I just stated has nothing to do with ACRs in general nor Blue Sea's.

That's just how charging lead batteries works, no matter the equipment involved, inherent in the chemistry and physics.

Bow out if you like, but if you want to learn more, feel free to ask specific questions and I'd be happy to explain what you see as discrepancies.

PS corrected "combing" to combining

Well, thank you John, but since you have demonstrated from this thread that you don't know very much about this topic, I probably won't have many questions for you.

 

[DavidM]

Well, I don't want to jump into that interesting sharing of views, but i would like to describe what happens in a typical multi-battery house system with a start battery connected through an ACR.

Let's assume that you have a 100 amp high output engine alternator with an external three step regulator directly connected to 4 golf cart batteries (440 Amp hours at 12v) and a Group 31 starting battery connected through a Yandina or one of the simple Blue Seas ACRs. And let's also assume that the house battery bank is about half charged.

When you first start the engine the alternator "sees" a low impedence load in the house batteries so it tries to supply its maximum current of about 100 amp. The alternator/house bank voltage is probably something in the mid 12s initially. Since it is well below the combine point, the two banks stay disconnected.

Then over an hour or two as the house bank rises to maybe 75-80% full its impedence rises and the current drops and the voltage rises. It eventually gets to 13+ volts and the combiner relay kicks in and combines the two banks. If the starting battery was full it doesn't affect anything. The voltage continues to rise to about 14.5 volts and the current drops off to the 20-30 amp range. Then the regulator finally kicks off and goes into float mode and holds in the mid 13 volts. Both batteries are still connected through the ACR since the voltage is above its combine point and the charging current is low.

If the starting battery were significantly discharged when the foregoing occurs it might put enough low impedence in the circuit to drive the voltage down. If it goes below 12.8 or so the combiner will kick off. This cycle will be repeated 2-3 times until the start battery builds up enough charge so that the combiner stays combined and both batteries build up charge until the regulator switches to float.

I hope that you all can see that the actions of the combiner/ACR are entirely based on the voltage it sees, nothing else.

Blue Seas does have more sophisticated ACRs that the sales literature says: "Automatically Manages the Charging of (2) Battery Banks" whereas the simple ACR just says that it combines the two banks. Your guess is as good as mine as to what the quoted statement really means.

David

 

[Delfin]

Well, I don't want to jump into that interesting sharing of views, but i would like to describe what happens in a typical multi-battery house system with a start battery connected through an ACR.

Let's assume that you have a 100 amp high output engine alternator with an external three step regulator directly connected to 4 golf cart batteries (440 Amp hours at 12v) and a Group 31 starting battery connected through a Yandina or one of the simple Blue Seas ACRs. And let's also assume that the house battery bank is about half charged.

When you first start the engine the alternator "sees" a low impedence load in the house batteries so it tries to supply its maximum current of about 100 amp. The alternator/house bank voltage is probably something in the mid 12s initially. Since it is well below the combine point, the two banks stay disconnected.

Then over an hour or two as the house bank rises to maybe 75-80% full its impedence rises and the current drops and the voltage rises. It eventually gets to 13+ volts and the combiner relay kicks in and combines the two banks. If the starting battery was full it doesn't affect anything. The voltage continues to rise to about 14.5 volts and the current drops off to the 20-30 amp range. Then the regulator finally kicks off and goes into float mode and holds in the mid 13 volts. Both batteries are still connected through the ACR since the voltage is above its combine point and the charging current is low.

If the starting battery were significantly discharged when the foregoing occurs it might put enough low impedence in the circuit to drive the voltage down. If it goes below 12.8 or so the combiner will kick off. This cycle will be repeated 2-3 times until the start battery builds up enough charge so that the combiner stays combined and both batteries build up charge until the regulator switches to float.

I hope that you all can see that the actions of the combiner/ACR are entirely based on the voltage it sees, nothing else.

Blue Seas does have more sophisticated ACRs that the sales literature says: "Automatically Manages the Charging of (2) Battery Banks" whereas the simple ACR just says that it combines the two banks. Your guess is as good as mine as to what the quoted statement really means.

David

What he said.

 

[dhays]

The ACR senses the voltage at the primary bank. You can wire them up backwards so that the charge source goes to the starter bank, then you would likely get the behavior that John thinks is correct, but if you do it this way you defeat the entire purpose of the device.

On my system, what you describe never happened through hundreds of cycles. I now have LiFePO4 batteries, which are managed differently, but the AGM house bank I maintained for 11 years when, depleted and a charge source applied, would accept charging current for quite a long time before the circuit would close and the starter bank was also charged. That was the expected behavior and I never saw a "premature" combination of the banks, at least as far as I can recall.

That certainly is not the behavior that I have experienced with a Blue Seas ACR nor what it is designed to do as I understand it.

As normally installed, the charge source is wired to the house bank. The ACR is connected between the house and start (or other bank of your choice). When the ACR sees the charging voltage as higher than the threshold (13.2-13.7v) it connects the two batteries. As soon as the charging stops and the voltage drops, then the ACR disconnects the two banks.

The ACR does NOT sense the SOC of the house bank in this scenario.

 

[dhays]

Many say not to use a 1/2/B/Off switch. I suggest that they can be used just fine, if wired correctly. Here is a diagram (rough) of how I setup my sailboat. The boat came with a 1/2/B/Off switch as well as an On/Off switch. The boat was delivered with 2 house batteries and no start battery. I used the existing switches as in the diagram.

The Alternator and the charger are wired to the house bank. An Echo-charger is used to charge the start battery. The 1/2/B/Off switch is wired so that when connected to "1" the House bank feeds the DC panel. The start battery is connected to the starter with the On/Off switch.

The 1/2/B/Off switch is left in the "1" position. The On/Off switch is left in the On position.

The switches can be used to switch between house and start if either of the batteries fail. Otherwise, the switches don't need to be touched unless you want to turn power off for some reason.

 

[Delfin]

That certainly is not the behavior that I have experienced with a Blue Seas ACR nor what it is designed to do as I understand it.

As normally installed, the charge source is wired to the house bank. The ACR is connected between the house and start (or other bank of your choice). As soon as a charge source is applied to the house bank, the ACR sees the charging voltage and connects the two batteries. As soon as the charging stops and the voltage drops, then the ACR disconnects the two banks.

The ACR does NOT sense the SOC of the house bank in this scenario.

Yes, the house bank is the primary bank and that is where the charge source is wired to. I mentioned that you can eff it up and wire the charge source to the starter bank and then you might get the behavior John was talking about, but also as I said that would be defeating the point of the device.

If the house bank is already charged when you power up a charge source, then the voltage could quickly hit the combine voltage, but under that scenario, you don't need the device in the first place. The intended behavior, as described in the snippet I provided from Blue Sea is as described by myself and djmarchand. The banks are only combined when the house, or primary bank, has reached the combine voltage.

If yours isn't behaving this way, then something is amiss in your system.

Just FYI, but to verify that I am not mistaken, I called Blue Sea technical support and they confirmed the operation I've described and experienced on my unit. That said, mine is a part number 9112, which has been replaced with the ML series. The technician couldn't find the reference on mine but thought that the "combine" voltage might be slightly higher on the 9112 than the ML, so it is possible that an ML would combine sooner than the older unit, but again, he wasn't sure.

 

[diver dave]

What he said.

Dare I enter this fray

But one point of correction. As a battery charges, its impedance drops. What rises, is its open circuit voltage. And, that is what drops the charger current.

The internal R drops by about a factor of two from 20 to 100% SOC.

https://pdfs.semanticscholar.org/5740/f9fbdd1430d3732eda6c93b59eaea4f9f87f.pdf

back to your regular programming.

 

[DavidM]

That certainly is not the behavior that I have experienced with a Blue Seas ACR nor what it is designed to do as I understand it.

As normally installed, the charge source is wired to the house bank. The ACR is connected between the house and start (or other bank of your choice). When the ACR sees the charging voltage as higher than the threshold (13.2-13.7v) it connects the two batteries. As soon as the charging stops and the voltage drops, then the ACR disconnects the two banks.

The ACR does NOT sense the SOC of the house bank in this scenario.

You said everything I said.

I did not say that the ACR sensed the SOC directly. I only gave SOC numbers because they influence internal impedence of the battery and therefore the charging voltage required to push an ever decreasing current into the batteries.

David

 

[DavidM]

Dare I enter this fray

But one point of correction. As a battery charges, its impedance drops. What rises, is its open circuit voltage. And, that is what drops the charger current.

The internal R drops by about a factor of two from 20 to 100% SOC.

https://pdfs.semanticscholar.org/5740/f9fbdd1430d3732eda6c93b59eaea4f9f87f.pdf

back to your regular programming.

I beg to differ. If the impedence drops as the battery builds up charge, the current would rise if the voltage were the same. The opposite is what happens. As the battery charges, its impedence rises so that it takes ever increasing voltage to drive the same current. That is what drives the voltage to hit 14.5 or so, then the regulator switches to float and drops to about 13.5.

David

 

[dhays]

If the house bank is already charged when you power up a charge source, then the voltage could quickly hit the combine voltage, but under that scenario, you don't need the device in the first place. The intended behavior, as described in the snippet I provided from Blue Sea is as described by myself and djmarchand. The banks are only combined when the house, or primary bank, has reached the combine voltage.

You said everything I said.

I did not say that the ACR sensed the SOC directly. I only gave SOC numbers because they influence internal impedence of the battery and therefore the charging voltage required to push an ever decreasing current into the batteries.

I think David's explanation a bit earlier likely explains why an ACR may not combine the batteries as soon as the engine is started up.

Maybe the issue is one of semantics but I would disagree with the sentence that I highlighted. The ACR will combine the banks when it senses the threshold voltage. This voltage is coming from the charging source, not the primary bank. A fully charged battery will be around 12.6(?) volts, but the alternator will put out close to 14v. It is the voltage from that alternator, or other charging source, which triggers the combiner.

 

[diver dave]

I beg to differ. If the impedence drops as the battery builds up charge, the current would rise if the voltage were the same. The opposite is what happens. As the battery charges, its impedence rises so that it takes ever increasing voltage to drive the same current. That is what drives the voltage to hit 14.5 or so, then the regulator switches to float and drops to about 13.5.

David

A guy named Thevenin had this figured out long ago.

When your LA battery is being charged, it affects the battery in two ways. First, the open circuit voltage rises, due to the chemical changes occuring. Second, those same changes reduce the R of the battery. The OC voltage (Vb) rise is a much greater affect than the R reduction. As fed from a constant voltage source (Va;alternator with regulator), the current is a function of Both voltages, the battery R1 and the wiring R2. So, the current equation is I=(Va-Vb)/(R1+R2).

The numerator will have the much more significant effect.

ps: internal R and V are the ONLY items in a battery that determine how powerful it is for starting current. An 8D has much less R than a GR 24, etc. And, a charged battery has more starting current, ie less R.

 

[psneeld]

it didnt in my case....

if the battery bank is low enough, even if the alternator is trying to put out 14 plus volts, the voltmeter reading where you have it hooked up to could still be below 13V... thus tbe chattering effect many of us have experienced and Blue Sea describes.

 

[dhays]

it didnt in my case....

if the battery bank is low enough, even if the alternator is trying to put out 14 plus volts, the voltmeter reading where you have it hooked up to could still be below 13V... thus tbe chattering effect many of us have experienced and Blue Sea describes.

That is what I think David was explaining earlier and may be the reason for the behavior that Delfin was seeing?

 

[Delfin]

I think David's explanation a bit earlier likely explains why an ACR may not combine the batteries as soon as the engine is started up.

Maybe the issue is one of semantics but I would disagree with the sentence that I highlighted. The ACR will combine the banks when it senses the threshold voltage. This voltage is coming from the charging source, not the primary bank. A fully charged battery will be around 12.6(?) volts, but the alternator will put out close to 14v. It is the voltage from that alternator, or other charging source, which triggers the combiner.

Since the charge source is directly connected to the primary bank (or should be, methinks), I'm not sure how you would detect a difference between the primary bank and the charge source. With my AGM bank, when discharged 25%, a 140 amp 24 vdc alternator would be putting out around 26.8 volts or so while the batteries accepted 120 amps, and measured voltage would creep up as the CAR declines and the battery gets charged. At 27.2 volts, or thereabouts, the banks would be combined, but at that point the house bank was 90% charged. Sounds like your experience is different, but I believe mine is the predicted behavior. While the alternator can put out 28 volts easily enough, it certainly doesn't start there on a discharged battery, which is why the combine voltage isn't reached until the house bank is getting charged up.

 

[psneeld]

pretty much with the smaller Blue Seas ACRs, you have to have the primary charging going to the larger, more deeply discharged bank....otherwise chatter.....at least thats what kept happening to me.

thats not what I wanted to do .... so I just put in an on/off switch between the start and house banks that gets switched every time I check the oil. Right before start, snd right after shutdown.

 

[Delfin]

pretty much with the smaller Blue Seas ACRs, you have to gave the primary charging going to the larger, more deeply discharged bank....otherwise chatter.....at least thats what kept happening to me.

thats not what I wanted to do .... so I just put in an on/off switch between the start and house banks that gets switched every time I check the oil. Right before start, snd right after shutdown.

I've never experienced chatter. The hysteresis between combine and open voltages is great enough if you were experiencing chatter, something seems wrong someplace.

 

[DavidM]

Ok, I think I can resolve the conflict between what Diver Dave is saying and what I am saying.

DD is talking about battery internal resistance, I call it impedence, when SUPPLYING current. Yes impedence drops as a battery reaches 100% SOC. A fully charged battery can supply more current when fully charged, even after adjusting for its higher OC voltage.

I was talking about internal impedence for a battery ACCEPTING current, ie charging. It rises as the battery gets more fully charged.

The two are no doubt related and I will bet there is some electrochemical explanation for this phenomenon, but those brain cells died a long time ago ;-).

David

 

[diver dave]

Ok, I think I can resolve the conflict between what Diver Dave is saying and what I am saying.

DD is talking about battery internal resistance, I call it impedence, when SUPPLYING current. Yes impedence drops as a battery reaches 100% SOC. A fully charged battery can supply more current when fully charged, even after adjusting for its higher OC voltage.

I was talking about internal impedence for a battery ACCEPTING current, ie charging. It rises as the battery gets more fully charged.

The two are no doubt related and I will bet there is some electrochemical explanation for this phenomenon, but those brain cells died a long time ago ;-).

David

One of the chemical process' that is occuring is a change of water into sulphuric acid. The acid being more conductive. This lowers the R.

Here is something you can try easily. Take a fully charged battery, still on a float charger, perhaps reading 13.6V or so. Being fully charged, its float current is non-zero, but quite low. Now, still with the voltmeter attached, remove the charger. You will see that 13.6 for a short bit, before starting to head down as the "surface charge" dissipates. That initial voltage you just measured is the Voltage "fighting" the charger, making the charge current so low. But, in fact, the internal R of the battery is at its lowest point.
You can prove that one too, but takes a significant load, like a starter motor or carbon pile.

ps: this "surface charge" is a real voltage, but has very little current carrying capability. Maybe that is the source (no pun) of confusion.