ACR and Atomic 4

[rigspelt]

Warning: I am an amateur on the learning curve with this stuff.

Steve and I are figuring out how to live with ACR-based charging systems on our boats. He proposed that we start a thread on this topic, so here goes.

My tentative charging/ignition schematic, showing the ACR:

http://www.moyermarine.com/forums/showthread.php?t=2695

My tentative ignition panel schematic:

http://www.moyermarine.com/forums/showthread.php?t=2727

The ACR Steve and I are using:
Blue Sea ACR 7610
Combiner battery switch 5511e
(both in kit 7650 http://bluesea.com/category/2/productline/overview/329)
Basic circuit with this kit: http://bluesea.com/files/images/products/7650.jpg. I am not endorsing this kit, it just happened to be available at a good price, and seemed to do what I want. Nor do I have any connection with Blue Sea.

There is an interesting thread on this in the Whaler forum:

http://continuouswave.com/ubb/Forum6/HTML/001232.html

For discussion, let's assume a simple system on 20's foot sailboat:
Two batteries, both the same age, type and brand.
One battery in a house circuit, the other battery dedicated to engine start only.
The battery combiner switch is ON-OFF-COMBINE.
The ACR is not in the engine starter circuit. One cable goes to the engine battery (+) post, the other goes to the house battery (+) post. When the battery being charged gets up over 13-something volts, the ACR turns on and parallels the two batteries, allowing the second battery to be charged as well as the first.
The alternator output goes to the engine start battery.
The shore power output goes to the house battery. Shore battery chargers usually have multiple outputs and are smart enough to charge different batteries separately. This is an issue when there is an ACR paralleling the two batteries.

Some issues:

1. Ignitiion panel voltmeter should be set to measure what? If across the (+) Battery terminal on the ignition key and (-) ground, then when the ACR is off it will measure voltage in the engine start battery circuit, but when the ACR is on it will measure the combined voltage of both batteries. That's OK by me, because all I want to know is that the alternator is charging, but not over-volting.

2. Engine start battery dies at anchor for some reason. I can combine the batteries to start the engine using the battery swtich set to COMBINE and then put the switch back to ON when the engine starts. The alternator will then provide electricity to keep the engine running, but if the voltage on the engine start battery remains below 13, the ACR will not parallel the batteries and the house battery will not get a charge. In that situation, should the battery switch be left in COMBINE, continuously paralleling the engine and house circuits?

3. The boat has a dual-output shore power charger to maintain the two batteries independently. Some chargers do not mind having their outputs paralleled, although that defeats the purpose of paying for an expensive multibank charger. Blue Sea has posted two tech papers on their website to provide solutions. I went with using two batteries the same and simply attaching one of the two shore power output cables (to the house battery). My logic is that because both batteries are the same, they can be treated as one battery for all intents and purposes.

4. Measuring current. I took the ammeter out of the ignition panel and now have an ammeter in the cabin. It is easy to interrupt a cable to insert an ammeter shunt in any circuit (just costs money and time), but I decided to put the shunt in the house battery ground cable, following Blue Sea's recommendation. A handheld clamp ammeter is not expensive and can be used to check currents in other circuits as required. I have a set of notes for interpreting the ammeter readings for different ACR states.

5. The ACR will not combine unless the charging system has an output voltage that will get the batteries above the ACR's threshold volts. My old 35 amp alternator only put out 13.1 volts, so I upgraded to the MMI 55 amp alternator which should produce over 14.

There is much to discuss.

[SEMIJim]

I was going to go with the same Blue Sea kit on our boat. Then it was pointed-out to me there's one potentially fatal scenario with ACRs: You run your house bank down. You start the engine. Requisite charging voltage is reached. ACR combines the banks. Soon thereafter the engine stalls/dies for some unrelated reason. You try to re-start. All you get is *click* - and maybe not even that. Your start battery is drained?!?! How can that be? Easy: When the ACR kicked-in, your start battery tried to charge your depleted house bank. In such a scenario, the contribution from a puny little 35A, or even 55A alternator is going to be inconsequential.

Unlikely scenario? Perhaps. But you know how Murphy is .

So instead I'm going with the same Blue Sea switch, but using a Xantrex Echo Charge instead. As for my dual-"channel" Xantrex (shore power) charger: I'll just not use the second "channel" anymore. I'll let the Echo Charge divvy it up.

Jim

[sastanley]

????

I am also VERY new to this, as I've always used boats with a simple 1-2-all switch, and I would set the switch to the battery I wanted to charge, making sure the engine was at idle and never switch thru Off. Combiners worry me a little bit too, an example that semiJim mentions above...if they are combined and you ran the house down (or if the house is shorted and won't maintain a charge, which is the issue I currently have), does it drain the good (start) battery?

My boat has a simple isolator (for which I found the instruction manual digging around in the bags of stuff I brought home off the boat!) and all it does is keep this from happening, dragging a good battery down during discharge (I think).

I have also contemplated the fact that I just don't think my old boat currently has enough electronics aboard to worry about a fancy electrical system. I will however, follow this thread and throw in my $0.02 when something piques my interest. I liked rigspelt's idea of tossing the ammeter into the cabin, which I plan to do, somewhere between the alt. & the battery bank...i think.

-Shawn

[HOTFLASH]

Acr?

So, what is an ACR?
Mary

[High Hopes]

Hi Semi Jim,

The scenario you described is exactly what the ACR is supposed to prevent. I had a very low voltage house battery, and the ACR never did connect to it. At first I couldn't figure out why the house battery wasn't charging. But it turned out that the ACR was behaving as designed.

The ACR model I am using has a low voltage drop-out (10.8 volts) feature. If for some reason the alternator can't keep connected batteries at 10.8 volts, the ACR will disconnect them. I don’t know if all ACRs have this feature. My model is brand new so it probably has all the latest technology. I can't comment on any other models.

When I connected the batteries together manually, the house battery began charging. I could hear the strain on the engine. After a while, I could open the battery switch without the ACR dropping out.

I took me a while to figure this out. That is why I need to come up with the gauges or procedures for troubleshooting what is wrong when the ACR isn't connecting the batteries. I don’t want to think about this at sea.

Steve

[sastanley]

Hi Mary,
That is one I can answer - ACR = Automatic Charging Relay.
Blue Sea is a popular brand..here is a link.

http://bluesea.com/category/2

-Shawn

[High Hopes]

Shawn,

...if they are combined and you ran the house down (or if the house is shorted and won't maintain a charge, which is the issue I currently have), does it drain the good (start) battery?

Good question! Yes, but it will only drain it down to 12.5 volts, after which time the ACR will drop out. You have me thinking.

There is a control pin on the ACR which can be wired to the ignition power. This wiring will allow the ACR to operate only when the engine ignition is ON which is, of course, when the battery is charging. After all, ACR = Automatic CHARGING relay. Thanks for the question. You just saved me from a bunch of headaches. New rule: The ACR should only do something when you are actually charging the batteries.

Isolation diodes prevent the batteries from ever seeing each other. This will stop one battery from draining the other.

Steve

[High Hopes]

Rigsy,

I just updated the spreadsheet in the spreadsheet message. My head is about to explode what with thinking about this stuff, but I think I have it tacked, not nailed, down. I will also re-post the spreadsheet to the same URL.

1. Ignition panel voltmeter should be set to measure what? If across the (+) Battery terminal on the ignition key and (-) ground, then when the ACR is off it will measure voltage in the engine start battery circuit, but when the ACR is on it will measure the combined voltage of both batteries. That's OK by me, because all I want to know is that the alternator is charging, but not over-volting.

You may want to be able to the house battery when the ACR is off. This would be helpful diagnostic information when troubleshooting.

2. Engine start battery dies at anchor for some reason. I can combine the batteries to start the engine using the battery switch set to COMBINE and then put the switch back to ON when the engine starts. The alternator will then provide electricity to keep the engine running, but if the voltage on the engine start battery remains below 13, the ACR will not parallel the batteries and the house battery will not get a charge. In that situation, should the battery switch be left in COMBINE, continuously paralleling the engine and house circuits?

Better to not combine the batteries. All charging current will go to the engine battery where it is most needed. When the engine battery is charged, the ACR will kick in and the house battery will be charged. Besides, the house battery doesn't need a charge; it just started the engine.

Peace, Steve

[rigspelt]

Rigsy, I just updated the spreadsheet in the spreadsheet message. My head is about to explode what with thinking about this stuff, but I think I have it tacked, not nailed, down. I will also re-post the spreadsheet to the same URL.

Good chipping, Steve. We'll get there.

You may want to be able to the house battery when the ACR is off. This would be helpful diagnostic information when troubleshooting.

I have dual voltmeters on my new Blue Sea DC panel, one for the house battery and one for the engine battery. I think it is possible to wire a manual switch to ensure the ACR is kept off, say for diagnostic purposes. Looks like they recommend interrupting the ACR ground wire: http://bluesea.com/category/2/productline/docs/387 and click on Technical Briefs, Multiple output battery chargers. What may be an earlier version of a Blue Sea Technical Brief said "See instructions for the ACR you are using, but all ACR’s can be disabled by disconnecting the negative connection." (Check carefully with an authority before trying this at home.)

Better to not combine the batteries. All charging current will go to the engine battery where it is most needed. When the engine battery is charged, the ACR will kick in and the house battery will be charged. Besides, the house battery doesn't need a charge; it just started the engine.

I agree that, if the ACR is working properly, the Combiner switch probably should be turned back to ON from COMBINE after starting, to recharge the engine battery from the alternator and prevent ongoing drain from house battery to engine battery. (Presumably this does not risk the alternator's diodes the way turning through OFF would?) This approach would be OK if the house battery has enough juice left to power the house circuits when it is not being charged by the alternator while under way. The house battery provides power to the navigation instruments, lights, etc, and the engine battery supplies power to the engine electronics, so both circuits have to remain open, and both batteries have to be charged before they drain down. House loads under way on a small sailboat are usually very small though, if an autopilot and radar are not running. From what I can tell reading between the lines at the Blue Sea website, the 5511e Combiner switch can be left in Combine mode to manually parallel the circuits if necessary. Whether that would be necessary would depend on the circumstances at the time, like relative state of the batteries, condition of the ACR, condition of the fuses and wiring, etc. If the engine battery can be charged up within afew hours and the house battery has sufficient charge to carry on without the alternator during that time, then there would be no need to manually combine the circuits, and all the alternator output could go to the engine start battery.

One downside of manually combining the circuits long term would be that engine circuit currents could contaminate house circuits when they are paralleled, either manually using the Combine switch, or automatically using the ACR. But for decades, many A4 boats had shared house and engine circuits.

I think you're right: we gain simplicity using the Combiner switch and ACR when everything is working right, but things get complex if something goes wrong. So, like you, I am working on a troubleshooting protocol for various situations. Your spreadsheet is a good idea.

[rigspelt]

Rigsy, I drafted a failure analysis spreadsheet. Take a look. Here is a screen shot and a link. I'd like to map this out so I know what to do when at sea. I guess ACRs simplify operation but complicate troubleshooting.http://gladucalled.com/ACR.xls
.

Steve,

Great start! Some suggestions:

Can you date the image, so that as you update it in that post we can relate subsequent comments to the correct version?

At the top, alongside the ACR Relay column, you might want to:
1. Name the ACR model your spreadsheet applies to.
2. List the ACR LED states: On when the ACR is combining the batteries, Off when the ACR is off, and blinking when the ACR senses that the lower battery is at 10.8 volts (ACR goes into lockout state and will not parallel).

You might want to include a column to indicated whether on alternator or on shore power (or in your case solar power, which is the same thing). The column heading could be "Charging Source", and the options could be either "Alternator" or "Other").

In the version up today, for "house battery sagging", I presume the system is on alternator, and the alternator output is connected to the engine start battery? If so, then I would expect the ACR to parallel the batteries when the engine start battery voltage gets above the ACR trigger threshold.

In the "battery overcharge" situation, I would stop the engine, disable the alternator by removing its belt if I thought I could restart the engine so that it quits overcharging the batteries, set sail, ensure the batteries are isolated, conserve power, and reserve the engine start for maneuvering in port. Or better yet, swap out the blown alternator for the spare.

You might want to change "Battery Overcharge" to "Overcharging"?

You might want to change "Losing Power" to "Undercharging"?

[sastanley]

Shawn,



Good question! Yes, but it will only drain it down to 12.5 volts, after which time the ACR will drop out. You have me thinking.

There is a control pin on the ACR which can be wired to the ignition power. This wiring will allow the ACR to operate only when the engine ignition is ON which is, of course, when the battery is charging. After all, ACR = Automatic CHARGING relay. Thanks for the question. You just saved me from a bunch of headaches. New rule: The ACR should only do something when you are actually charging the batteries.

Isolation diodes prevent the batteries from ever seeing each other. This will stop one battery from draining the other.

Steve

Man, you guys have my head spinning! I have "isolation diodes" in between the alternator and the batteries now, which allows me to not have to worry about switching the battery switch when the engine is running. Do I still need an ACR?

[High Hopes]

Do I still need an ACR?

Stan,

No you do not need an ACR. Given the added complexity of troubleshooting, I am beginning to wonder if I should have one.

The diodes are a great idea, except that, theoretically, the voltage drop across the diode, 7/10 volt, doesn't quite let the batteries charge as quickly or as much without the diodes. This is the theory. In practice, it probably makes little difference. I have an Electrical Engineering background and a lot of troubleshooting skills, so I ventured forth on the ACR path. I'm am not sure if this was a good move and I now find myself wishing I had chosen the diode path.

The normal battery switch for the ACR is completely different from the usual battery switch. So don't panic about what is said here. The designs are different and do not correlate with each other. To make matters worse, I am using a standard battery switch, not the usual ACR model. But I'm not using the standard battery switch in the standard configuration.

B bl la, B bl la, B, bl la (Waving my index finger up and down over my lips like Elmer Fudd).

Steve

[High Hopes]

Rigsy,

On your 5:18 AM post, I think we are walking along the same path. But be advised that I use a regular 1 2 BOTH battery switch in my design, but not in the standard configuration. The common terminal is not attached to the alternator, but to Battery 2. This battery gets switched to the house circuits or to the engine (for combining).

Basically this switch is used as an ON/OFF switch for the house devices. The ignition key is my ON/OFF switch for all the engine circuits.

Steve

[High Hopes]

Can you date the image, so that as you update it in that post we can relate subsequent comments to the correct version?

At the top, alongside the ACR Relay column, you might want to:
1. Name the ACR model your spreadsheet applies to.
2. List the ACR LED states: On when the ACR is combining the batteries, Off when the ACR is off, and blinking when the ACR senses that the lower battery is at 10.8 volts (ACR goes into lockout state and will not parallel).

Rigsy,

These are good suggestions - will do.

You might want to include a column to indicated whether on alternator or on shore power . . .

My solar panel is always connected, so I haven't explored this variation. I never use a shore charger, or a 12 volt DC power supply. If you post something, I will be glad to review it with you.

In the "battery overcharge" situation, I would stop the engine, disable the alternator by removing its belt. . .
You might want to change "Battery Overcharge" to "Overcharging"?
You might want to change "Losing Power" to "Undercharging"?

Good ideas. I will update the spreadsheet.

Steve

[rigspelt]

Man, you guys have my head spinning! I have "isolation diodes" in between the alternator and the batteries now, which allows me to not have to worry about switching the battery switch when the engine is running. Do I still need an ACR?

As Steve said, a battery isolator setup is a perfectly valid way to manage a pair of batteries. It's older, but venerable and works. The newer systems have advantages for the technically inclined, but if your system works, why change it? Blue Sea discusses isolators vs ACRs here: http://bluesea.com/viewresource/92.