ACR and 3 Battery Banks - Will this work?

[mashenden]

I am installing a Blue Sea Add-A-Battery (which is a Dual Circuit battery switch and an ACR). I have 3 battery banks (all wet cell) as follows; Starting, House, and Deep Cycle (the latter is dedicated to the 12V fridge). I will connect the Starting battery as per the Blue Sea diagram (in other words Starting on the A side of the ACR and #2 side of the Dual Circuit battery switch).

My question is whether I can redeploy the old A/B battery switch by connecting it to the B side of the ACR and then connecting the House battery to one side of the A/B Switch (1 or A), and the Deep Cycle to the other side of the A/B Switch (2 or B). The idea being to have the option to switch the B side of the ACR to one or the other of the House or Deep Cycle battery banks

I envision that the Starting battery and which ever battery is switched to the B side of the ACR will self maintain. Then if I have been motoring for a while, I can manually switch charging to the "neglected" battery bank (House or Deep Cycle).

Here is my electrical diagram. The Battery Charger is connected to all 3 batteries to make sure that one bank is not neglected while powered from shore.

Any concerns come to mind?

[hilbert]

From what I've read, the TRUECharger2 only has one output setting and it is assumed that all the battery banks have the same battery chemistry and can tolerate the same charge sequence and voltage/current ratings (the three outputs are just divided equally). In such a case, the outputs can be jumped together to create a single output. Typically, all the current from the battery charger and the alternator would be fed to the house bank and the smaller starting battery would be charged via an ACR relay. With this arrangement, I would connect one side of the ACR to the house bank and the other side to the A/B battery switch to select between charging the starting battery or the deep cycle refrigeration battery. But, it would be simpler and more reliable to have a properly sized house bank supply the power for refrigeration, without having the third dedicated battery. JM2CW

References:
Preventing Cycling in Battery Combiners, https://www.bluesea.com/resources/527
Compass Marine How To Article, Installing A Marine Battery Charger: http://www.pbase.com/mainecruising/inst ... ry_charger

Also, I'm envious of the isolation transformer!

[Maine Sail]

I am installing a Blue Sea Add-A-Battery (which is a Dual Circuit battery switch and an ACR). I have 3 battery banks (all wet cell) as follows; Starting, House, and Deep Cycle (the latter is dedicated to the 12V fridge).

I guess I need to understand why you think you want three banks. A low voltage cut off on the fridge circuit will allow you to add capacity to the house bank and make the whole system more efficient, less complicated and the house bank will be cycled less deeply than the third bank would. Adding capacity to the house bank is usually the best approach rather than adding yet another bank.

I will connect the Starting battery as per the Blue Sea diagram (in other words Starting on the A side of the ACR and #2 side of the Dual Circuit battery switch).

This is not a wise way to install an ACR on a cruising boat when you have a deeply cycled bank. It can lead to what is called relay cycling. Lead all charge sources to the house bank first then use an ACR or ACR's to feed the start bank, or house #2, if you really, really must have a third bank......

My question is whether I can redeploy the old A/B battery switch by connecting it to the B side of the ACR and then connecting the House battery to one side of the A/B Switch (1 or A), and the Deep Cycle to the other side of the A/B Switch (2 or B). The idea being to have the option to switch the B side of the ACR to one or the other of the House or Deep Cycle battery banks

You could certainly do that but part of the automation & simplicity you've paid for with the DCP switch is now gone and large portion of your charge and battery management still remains manually controlled.

If you want to keep it automated simply add another ACR or use an Echo for start and ACR for the second house bank. Preferably just make the house bank larger and use one ACR to feed start, simple & done...

I envision that the Starting battery and which ever battery is switched to the B side of the ACR will self maintain. Then if I have been motoring for a while, I can manually switch charging to the "neglected" battery bank (House or Deep Cycle).

The house bank should be the bank getting the charge all of the time, especially with disproportionately sized banks and when one of them is deeply cycled... Once the house bank comes up to 13.0V, for more than 90, seconds the ACR will close and top off the start battery which should still be at 98-99.5% SOC anyway... The instructions for the DCP are really written for a center console with two mostly equal sized batteries on-board not for a large deep cycle house bank and a small starter battery....

Here is my electrical diagram. The Battery Charger is connected to all 3 batteries to make sure that one bank is not neglected while powered from shore.

I would advise you to get rid of the third bank, increase house bank capacity & wire all charge sources to HOUSE and then the ACR will always take care of the start battery whether on shore power, alternator, solar etc... If you are concerned about the house bank getting discharged in an accident simply install a low voltage cut off in the fridge circuit set somewhere between 12.0V - 12.2V..

Any concerns come to mind?

Just keep in mind that while the DCP (Dual Circuit Plus switch) is a very simple switch you give up any form of switch isolation of a bad battery or bank, unless you physically un-wire them. You have ON/COMBINE and OFF. With the original switch you could isolate a bad bank by simply switching to the other. I have had the DCP leave customers dead in the water because COMBINE was the only option..

If you can describe your use and what exactly you are trying to achieve with the system we can help more...

[mashenden]

Interesting food for thought. If I understand the responses correctly, the DCP/ACR is a bad idea for my application (which is a cursing boat).

My objectives are to 1) have battery power for the items that I need/want and 2) to minimize my effort to keep this sustained.

I prioritize my power needs as follows:

• Top priority - Starting
• Next priority - Electronics and LED lighting (House battery)
• Last priority - DC Refrigeration (Deep cycle)

When I do this process manually, I let the motor charge up the Starting battery for 15 minutes or until I remember (hence the need for an automated solution). Then I switch to the House bank for the rest of the time. Once I integrate the Deep Cycle into the picture, I would then switch to Deep Cycle once the House batteries have been brought up to full charge.

I am looking for something to automate as much of this as possible.

Regarding adding a Deep Cycle battery as opposed to sizing the House batteries appropriately, if the time was right to replace my House bank, I would head in that direction, but its not and these are not cheap batteries. Adding a Deep Cycle was cheap, and it has the added benefit of being a back-up solution for my dingy (using a trolling motor if the gas motor decides to not start). Given that upgrading my House batteries is not going to happen at this point in time, I like keeping the fridge separate from House since it is my lowest priority. I'd like to keep 3 banks in my design for these reasons.

Is there something out there that would emulate what I do manually (but not consistently because I forget)? In other words, after starting the motor, it would monitor the charge on a primary bank (Starting), then once it reaches a certain voltage for a period of time, switch to the next bank (House), then to the next (Deep Cycle)? If this process was automated, it seemingly would initiate that sequence every couple of hours.

[hilbert]

Interesting food for thought. If I understand the responses correctly, the DCP/ACR is a bad idea for my application (which is a cursing boat).

There is more "cursing" than "cruising" on my boat as well.

Matt, whatever works for you is the correct setup. The simplest and best solution might be a timer to remind you to take the appropriate action.

[mashenden]

Interesting food for thought. If I understand the responses correctly, the DCP/ACR is a bad idea for my application (which is a cursing boat).

There is more "cursing" than "cruising" on my boat as well.
...

Oooops - too funny. That was definitely the case when many parts from my traveler went for a swim !!

[mashenden]

Matt, whatever works for you is the correct setup. The simplest and best solution might be a timer to remind you to take the appropriate action.

I hope not. With today's technology, it seems such a product would be worthy (unless I am missing something).

[Paul D.]

I concur with keeping the house bank as large capacity as possible and using an echo charger (<$130) between that and the starter battery. I have had that system, with a fridge, for twelve seasons. My fridge is also a low priority so I monitor it and the Link 10 monitor and shut off the fridge if ever needed. I'd say a pretty simple, reliable system.

[mashenden]

I concur with keeping the house bank as large capacity as possible and using an echo charger (<$130) between that and the starter battery. I have had that system, with a fridge, for twelve seasons. My fridge is also a low priority so I monitor it and the Link 10 monitor and shut off the fridge if ever needed. I'd say a pretty simple, reliable system.

I am not disagreeing that increasing the house bank is the preferred approach, but I am not going to replace perfectly good house batteries until time dictates. Hence the interest in using a deep cycle as an interim solution.

I am surprised that there isn't a device that directs all of the charging amps to Bank A, then once a full charge is achieved switch the full charge to Bank B, then Bank C once a full charge is achieved on B. It seemingly solves a lot of issues. It basically automates what I do manually, but less ideally because I do not switch at the proper times based on voltage. What am I missing??

For future reference when that time comes, does the Xantrex Echo do something different that the TrueCharge2 does not do?

[joemerchant]

I still agree that you are possibly over complicating things with the 3rd bank. Ideally, you would just add capacity to the house bank and work your way up to shorter cycles to keep them topped off and shorter cycles as much as possible. If you are adding solar to the mix, then that further complicates matters with multiple banks.

But, in the same position where we have two 8D batteries that are 5 years old in the house bank, but didn't want to replace them just yet as they are still holding and cycling well, I just put in two 6 volt trojans with a hard switch between for the piece of mind. Once we do decide to pull out the two 8D's, will just continue to add to the trojan bank to build the house up. Until then, it is just a backup where I can switch if the 8D's get too low or bite the dust before we can crane them out.

From what I am hearing, you are trying to do the same thing, but with a more complicated and permanent solution. Consensus really is siding on two banks on board, but if you have to add new to old like we are, I would say try and keep it simple and short-term.

[mashenden]

Again - not disagreeing with anyone (all) that is recommending 2 banks, rather than 3. I get it loud and clear, but the timing is not right. Certainly I am not the first person that wants to add a fridge but is not ready to discard the House batteries that still have notable life remaining.

So, not meaning to sound terse, but enough with the "2 banks are better" comments, please. I also get that I can do the switching manually, but I was hoping for a more automated solution than that.

Barring an automated solution I will forego the DCP/ACR Add-A-Battery idea given the dissimilarities between the Starting and House batteries (based on advice given earlier in this post), and simply do this by adding a manual switch between Bank B and Bank C. Its really not that complicated - just not automated.

Any automated solutions to my issue as presented, or a technical reason why an electronic device does not exist to do what I do manually would be greatly appreciated.

In case people are not reading my responses, I'll restate again what I think would solve my situation: A device that:

• After starting the motor (or plugging into shore power) directs all of the charging amps to Bank A (Starting).
• Then once a full charge is achieved switch the full charge to Bank B (House). This minimally would help automate things.
• Then it would be even better if it also had the option to switch to Bank C (Fridge Deep Cycle) once a full charge is achieved on B.

Cycling through this sequence every x hours to maintain all banks would also seemingly make sense.

[hilbert]

For future reference when that time comes, does the Xantrex Echo do something different that the TrueCharge2 does not do?

The Xantrex echo-charge has a function similar to an ACR, but it is more sophisticated and uses different criteria for when and how to connect the batteries. It is not a battery charger like the TrueCharge2, which uses AC to charge one or more banks of batteries.

ACR: connects two battery banks when the voltage of either battery bank is greater than X for Y seconds. It will disconnect the two battery banks when the voltage is less than W for Z seconds.

Echo: The echo is a voltage-follower that will share the charging of one battery bank with another. It follows the charge stages of the source battery bank (Bulk, Absorption & Float). It controls the current flow based on the voltage difference between the two banks.

[hilbert]

Any automated solutions to my issue as presented, . . .

Based on your description and Maine Sail's response, here is a configuration to achieve full automation as presented:

[mashenden]

Any automated solutions to my issue as presented, . . .

Based on your description and Maine Sail's response, here is a configuration to achieve full automation as presented:

Interesting. Thank you. I did not initially get that from Maine Sails response. Let me do some more research on Echos.

With this design in mind, is the concern about relay cycling put to rest because both the House and Deep Cycle batteries are used similarly (both are drawn down), albeit different in capacity? The use being the key difference as compared to connecting an ACR to a House bank and a Starting battery, where their uses are notably different (House is drawn down, while the Starting battery provides high amps for short period)?

[Maine Sail]

Again - not disagreeing with anyone (all) that is recommending 2 banks, rather than 3. I get it loud and clear, but the timing is not right. Certainly I am not the first person that wants to add a fridge but is not ready to discard the House batteries that still have notable life remaining.

Matt,

You came and asked advice and we are trying to help and sharing some best practices. I think some additional points should be considered....

#1 You've made no comments about a LVC device for the fridge circuit? This protects your existing house bank (or deep cycle) and will turn the fridge circuit off automatically on low battery voltage. These are used quite often on dock sailed boats where dock power brown outs are common and the owner wants to still leave the fridge on. When power comes back and the batteries re-charge the frigde comes back on too.

#2 Do you know that your existing house bank can't handle the fridge? Have you run the numbers? Do you have an Ah counter and do you know the fridges average daily draw? If you have two 6V batteries this is 225 - 400 +/- Ah's (depending upon size) and I have plenty of cruising boats using that type bank with refrigeration. By contrast a 12V battery will only be in the neighborhood of 75Ah - 125Ah depending if Group 24, 27 or 31. To 50% DOD from 100% SOC this means 37.5 - 62.5 Ah's of usable capacity. When off cruising however your bank will only really get back to about 80% SOC so that makes your usable fridge capacity of 22.5 - 37.5 Ah's of usable cruising capacity using the 50% to 80% cruisers rule due to battery acceptance limitations. If your fridge exceeds the 20 hour discharge rate of the battery you will also not get the Ah capacity you expect from it, due to Peukert effects.

#3 You don't say what 12V battery you want to use (brand & model) but if this is a typical Group 24, 27 or 31 these are not deep cycle batteries despite what the lies on the sticker tell you. Your 6V batteries are deep cycle but a 12V Group 24, 27 or 31 are not unless you go AGM or GEL which I would advise against in this scenario. I would urge you to read this before buying a 12V battery. 12V deep cycle batteries do exist, but they are not easily found or sourced.

What is a Deep Cycle Battery http://www.pbase.com/mainecruising/deep_cycle_battery

#4 Consider the total cost of the third battery install, done correctly, including wire, over current protection, split loom, terminal hats, wire ties, charge automation, terminals, heat shrink, switches etc. in the whole cost of the installation and I suspect you will find that two additional 6V batteries added to what you have (you said they were new-ish and in good shape) may come out to actually cost less. The average 6V golf cart battery runs $100.00 - $135.00 each and a single decent quality (though not really a deep cycle) 12V group 31 will run you in the $125.00 + range with premium batteries like the Trojan SCS-225 (group 31) running close to $200.00....

So, not meaning to sound terse, but enough with the "2 banks are better" comments, please. I also get that I can do the switching manually, but I was hoping for a more automated solution than that.

Automation is easy, and can easily be done (see Hilbert's post before this one). The problem arises with the added cost of components etc. & I would suggest that you could simplify at darn near the cost of the third bank.. We are trying to help you build a good system and I suspect that it can be cone at close to the cost of your third bank idea. If you are unwilling to move forward with any of these suggestions, that's fine its your boat.

I will however continue typing for others because you've brought up a couple of misunderstandings that do make for good discussion.

Barring an automated solution I will forego the DCP/ACR Add-A-Battery idea given the dissimilarities between the Starting and House batteries (based on advice given earlier in this post), and simply do this by adding a manual switch between Bank B and Bank C. Its really not that complicated - just not automated.

Here is where the misunderstandings enter in. You've assumed the ACR is a bad fit, but it is not. They just sometimes need a finer understanding of what they do and how they work. A link was posted earlier (not by me) to Wayne Kelsoe's (CTO Blue Sea Systems) excellent white paper on Relay Cycling. Here it is again.

https://www.bluesea.com/resources/527.

The ACR is a tremendous device for a cruising boat but it also needs to be wired properly for a cruising boat. If you want to cruise on a center console wire per the package insert-instructions. If you want to wire it for a cruising boat use the link I just posted and feed all charge sources to the HOUSE bank..

The instructions that ship with the DCP are not intended for a cruising boat. Any good marine electrician knows this but many a DIY and poor quality electrician do not. Due to misunderstanding the product they wire them incorrectly and wind up with issues of relay cycling. It is the number one blunder with ACR's that I fix for customers. With an ACR (or Echo) on a cruising boat all charge sources flow to the largest bank, which is HOUSE. The relay then combines/parallels to START...

Any automated solutions to my issue as presented, or a technical reason why an electronic device does not exist to do what I do manually would be greatly appreciated.

Yes an ACR or two or an ACR and a battery to battery charger such as the Echo charger. The ACR would charge the "deep cycle" from the house bank and the Echo would charge the START also from the HOUSE bank. Alternatively two ACR's can be used feeding from the house bank...

For future reference when that time comes, does the Xantrex Echo do something different that the TrueCharge2 does not do?

An Echo Charger is a charge management device or charge automation device. Unlike your battery charger the Echo is a battery to battery charger and can work with any charge source, just like an ACR does. Feed wind, solar, battery charger, alternator, hydro generator or even a fuel cell to the HOUSE bank and the Echo will charge the start battery. The battery charger needs 120V to work the Echo works battery to battery with any charging sosurce....

In case people are not reading my responses, I'll restate again what I think would solve my situation: A device that:

• After starting the motor (or plugging into shore power) directs all of the charging amps to Bank A (Starting).

"What I think" is another one of the misunderstandings surrounding boat electrical systems and batteries that many folks have, you are not alone on this.... Let me try to be not so foggy on this one..... NO !!!!!

Unfortunately this is one of the biggest misunderstandings boaters have about boats and batteries & charging. Sending all charge current to the start battery first, after starting, is really of no use at all and is actually detrimental to the efficiency of charging the batteries.. A start battery will barely use 0.5Ah to start a typical sailboat AUX motor therefore the bank hits limiting voltage nearly instantaneously and the charge current, after a very brief in-rush, rapidly declines to near zilch, usually in well under 1 minute. Sending charge current to the start first only serves to waste perfectly good charging time by charging an already FULL battery. The reason a device like this does not exist (though some are "marketed" as such) is because electrical engineers understand this would be like selling sunglasses to a blind guy, not really necessary except for fashion.

[*]Then once a full charge is achieved switch the full charge to Bank B (House). This minimally would help automate things.

When I do this process manually, I let the motor charge up the Starting battery for 15 minutes or until I remember (hence the need for an automated solution). Then I switch to the House bank for the rest of the time. Once I integrate the Deep Cycle into the picture, I would then switch to Deep Cycle once the House batteries have been brought up to full charge.

Again this is not at all necessary and not very rational if the goal is to charge the banks as fast as you can... You referenced 15 minutes of manually charging start.

Lets run that out with a 100A alternator. We will assume it can deliver 80A when hot.

15 minutes at 80A is 20 ampere hours of charging capacity you have just wasted by feeding it to a start battery for 15 minutes that is accepting less than 1A of charge current.... If your boats average house draw is 5A then you just chose to ignore close to 4 hours of discharge time in 15 minutes of not recharging the house bank.. The efficiency of the charging system is already suffering badly at just 15 minutes into it. Using a 100A alternator (really any alternator) to charge a battery taking 1A +/- for any length of time is inefficient and a waste of both time and fuel. Using the alternator at its max current potential for the longest time possible leads to the most efficient charging of the banks and overall system efficiency. This means all banks are being charge at the same time for the fastest charging. I wont even go into Coulombic efficiency which is just another impact on alternating charging...

[*]Then it would be even better if it also had the option to switch to Bank C (Fridge Deep Cycle) once a full charge is achieved on B.[/list]

You are referencing "full charge" like it is easily achievable, sadly it is anything but when off cruising.

To fully charge the house bank will take you upwards of SEVEN to TEN HOURS + of motor run time.

To fully charge the "deep cycle" bank will also take you SEVEN to TEN HOURS + of motor run time.

IF you alternate charging of the banks you really murder your charging system efficiency due to declining battery acceptance rates during absorption charging.. If you charge them all in parallel or one bank in parallel with an ACR and start bank with an ECHO, with all charge sources originating at the HOUSE bank, your charge times to full will still be longish but more than cut in half from "alternating" the charging.

We all know and hear how fast an AGM battery charges, and they do charge faster than flooded batteries.. This graph was data logged with a used but relatively healthy 125Ah AGM battery with a Charge rate of .2C or 20% of Ah capacity in charge current. The absorption voltage was held steady at 14.4V until the battery was 100% full, something the typical marine charging system almost never does because they drop to float prematurely thus extending charge times to 100% SOC.. It also did not suffer from voltage drop or varying charge current due to a hot alternator etc... This AGM battery still took over 7 hours to attain 100% SOC (as defined by the battery manufacturer) with perfect lab conditions. On a boat we do not have perfect lab conditions and this only serves to slow the charging process..

This battery spent 1:42 minutes in BULK and 5:24 minutes in ABSORPTION. Once your batteries come up to absorption voltage there is nothing you can do to make them charge any faster (unless of course you raised the voltage above manufacturer guidance). The last 10% is slow, the last 5% painfully slow and the last 3% excruciatingly slow. Still if you want your batteries to last you need to get them to 100% SOC as often as possible.

Cycling through this sequence every x hours to maintain all banks would also seemingly make sense.

Charging all the batteries together makes sense. Alternating them does not...