ACR and 3 Battery Banks - Will this work?

[mashenden]

So if I follow the Echo tech data correctly...

• When the House battery needs to be charged (The Input voltage is lower than 13 Volts), the Echo dedicates all of the current to the House bank.
• When the House battery is approaching fully charged (The Input voltage is between 13.0 to 17.0 Volts), the Echo lets some of the current go to the Starting battery to charge it. By "some" it lets 15 amps go to the Starting battery if the voltage difference is relatively small (1.5V diff), tapering down to 2 amps if the voltage difference is relatively large (10V diff).
• Then when the Starting battery is fully charged (reaches 14.4 volts), the Echo stops the current from going to the Starting battery.
• Then when the House battery is fully charged, the charger/alternator should start backing off

The only drawback I see (but I can live with it) is that it seemingly puts the House battery at a higher priority over the Starting battery. Is that right or am I missing something?

Should there be any concerns with the Starting battery not getting any charge if the House battery never becomes fully charged (House battery bank is failing or is draining quicker than the charge current)?

[Maine Sail]

So if I follow the Echo tech data correctly...

• When the House battery needs to be charged (The Input voltage is lower than 13 Volts), the Echo dedicates all of the current to the House bank.
• When the House battery is approaching fully charged (The Input voltage is between 13.0 to 17.0 Volts), the Echo lets some of the current go to the Starting battery to charge it. By "some" it lets 15 amps go to the Starting battery if the voltage difference is relatively small (1.5V diff), tapering down to 2 amps if the voltage difference is relatively large (10V diff).
• Then when the Starting battery is fully charged (reaches 14.4 volts), the Echo stops the current from going to the Starting battery.
• Then when the House battery is fully charged, the charger/alternator should start backing off

The only drawback I see (but I can live with it) is that it seemingly puts the House battery at a higher priority over the Starting battery. Is that right or am I missing something?

Should there be any concerns with the Starting battery not getting any charge if the House battery never becomes fully charged (House battery bank is failing or is draining quicker than the charge current)?

Stop thinking you need "priority" for the START....... (head banging firmly on wall)


The Echo 13.0V excite voltage is very, very, very far from a "full charge" it is very, very early bulk charging. The turn on point will depend upon how low you discharge the house bank (do not let any of your banks go below 12.0V) and how large your charge source is. For most house banks at 50% DOD, with a properly sized alt for the bank, the time to 13.0V is a four to ten minutes at best. In the graph above the time to 13.0V was 9 minutes on an AGM at a .2C charge rate starting at 50% DOD.

The Echo does not turn off at 14.4V and it "follows" the house bank charge profile. So if you have a 14.4V absorption for 4 hours on house the Echo also stays at absorption for four hours. It is a "voltage follower"... The Echo has a slight voltage drop across it so with HOUSE at 14.4V you will not see 14.4V on the START, but not all that far off.

People are always surprised when they see this video:


What Happens When I Start My Engine?

https://youtu.be/nrQXnqNOI9Q

[mashenden]

Stop thinking you need "priority" for the START....... (head banging firmly on wall)

Please don't bang head on wall - we will undoubtedly need the knowledge you are damaging

BTW - I posted my last response before seeing your latest. Its not that I am not getting this. I am just not as up to speed as you and I may miss things initially. Please have patience!

Challenging the Starting being first priority is a new concept for me, that just came to light - I will need to re-re-read your posts to fully get that tid-bit. Thank you.

[mashenden]

...
The Echo does not turn off at 14.4V and it "follows" the house bank charge profile. So if you have a 14.4V absorption for 4 hours on house the Echo also stays at absorption for four hours. It is a "voltage follower"... The Echo has a slight voltage drop across it so with HOUSE at 14.4V you will not see 14.4V on the START, but not all that far off.

...

Good catch - I had that wrong. Thank you.

I still need to come to terms with not worrying that the Starting battery is not the primary battery being charged (forgive me if I worded that less than ideally but hopefully you know what I mean).

[mashenden]

#3 ... 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

Wow - very interesting. I'll never waste my $$ on a 12V deep cycle again.

Here is where the misunderstandings enter in. You've assumed the ACR is a bad fit, but it is not. ...

Sort of... I didn't assume anything but I definitely misunderstood something. I am asking umpteen different questions because I don't like to assume. I do sometimes state things based on my current understanding that may still be wrong - that I am really good at!!

I now realize you were OK using an ACR and that the chargers should be connected to the House battery to reduce (prevent?) relay cycling, not that ACRs have no place on a cruising boat (or "cursing" boat as I inadvertently called it in an earlier post ).

I am still trying to understand the priority shift, and whether there is a chance that the ACR/Echo approach would potentially leave me stranded if the House bank started to fail, leaving the Starting battery uncharged (I'm not saying that it will - just that I want to understand why it would not).

[Maine Sail]

...
The Echo does not turn off at 14.4V and it "follows" the house bank charge profile. So if you have a 14.4V absorption for 4 hours on house the Echo also stays at absorption for four hours. It is a "voltage follower"... The Echo has a slight voltage drop across it so with HOUSE at 14.4V you will not see 14.4V on the START, but not all that far off.

...

I still need to come to terms with not worrying that the Starting battery is not the primary battery being charged .

Here's one for ya then. Nearly 70% of the sailboats I set foot on use the house bank for everything, both starting and house loads. The start battery is used as nothing more than a reserve battery ready and able but never really used except to test it every now and then.

Last year Sailboatowners.com conducted a Battery Use Survey where we had over 1000 responses from sailboat owners.. One of the interesting points was this:

*66% of all responders use the house bank for everything including starting

*33% of responders use a dedicated starting battery

That's pretty close to my 70% that use the house bank for everything...

[tjr818]

...Here's one for ya then. Nearly 70% of the sailboats I set foot on use the house bank for everything, both starting and house loads. The start battery is used as nothing more than a reserve battery ready and able but never really used except to test it every now and then.

That would be me It has always worked for us, but then again so has the house battery. We have never needed the "spare" . . . yet

[mashenden]

...
Here's one for ya then. Nearly 70% of the sailboats I set foot on use the house bank for everything, both starting and house loads. The start battery is used as nothing more than a reserve battery ready and able but never really used except to test it every now and then.
...

Damn - my world is getting turned upside down

I was under the impression, incorrectly so it seems, that Deep Cycle batteries were not really designed for the high current demand related to starting. Is that really not so, as it relates to House batteries (wet cell Rolls 6V x 2 type)??

On the rare occasion that I have used the House batteries to start the diesel, I always thought; Great, that was not a good idea. Lost hair and wrinkles for no good reason, you say?

[Maine Sail]

...
Here's one for ya then. Nearly 70% of the sailboats I set foot on use the house bank for everything, both starting and house loads. The start battery is used as nothing more than a reserve battery ready and able but never really used except to test it every now and then.
...

Damn - my world is getting turned upside down

I was under the impression, incorrectly so it seems, that Deep Cycle batteries were not really designed for the high current demand related to starting. Is that really not so, as it relates to House batteries (wet cell Rolls 6V x 2 type)??

On the rare occasion that I have used the House batteries to start the diesel, I always thought; Great, that was not a good idea. Lost hair and wrinkles for not good reason, you say?

I think Trojan Battery sums it up best:

Can I use my deep-cycle battery as a starting battery?

Deep-cycle batteries can be used for engine starting but starting batteries should not be used for deep-cycle applications. A deep-cycle battery may have less cranking amps per pound than a starting battery, but in most cases a deep-cycle battery is still more than adequate for the purpose of starting an engine.

This is especially true with our relatively small engines and large banks....

That said you are on the right track with using a dedicated starting battery, nothing wrong with it at all and I generally prefer it if not too costly and it makes sense for the needs... For a dedicated HOUSE and START I generally prefer a three ON/OFF switch layout HOUSE - EMERGENCY PARALLEL - START

Here is some good information on how to make your 1/2/BOTH switch a better performer too..

1/2/BOTH Switch Thoughts & Musings: http://forums.sbo.sailboatowners.com/sh ... p?t=137615

[Paul D.]

I've been following this post and maybe can sum up what seems to be clearing up anyway.

1. Find out if you have enough amp hours in your house bank for the fridge
2. If so, send all charging sources to the house bank - whatever that is at the moment, hopefully deep cycle
2a. If not, add Amp hour capacity to house bank
3. Wire an Echo Charger between the house bank and the starter - Really simple
4. When operating, Start motor on either all or start as you wish
5. Set battery switch to house and forget the world

On Femme, after our first season with two regular car batteries and full of constant worry about having enough charge we did exactly this though the Fridge was already aboard. I installed 2 Trojan T-105's, echo charger, 60w solar panel and regulator, Link 10 battery monitor and new start battery suitable for the Kubota 3 cylinder. Hardest part was building the longer battery shelf. We have not worried about power OR running down both banks since. My only need is to keep the battery switch on house. I prefer this to having an extra battery switch. I do give up the isolation though. In moments of supreme and inexcusable laziness or immediate excusable urgency, I've started the motor on the house bank without harm.

I have helped a lot of people with their boats systems over the years and seen some really complicated ones. I am a better sailor than mechanic so I tend to prefer keeping things simple, at the expense of having some modern extra precautions not needed for safety. This plan was recommended to me by a marine power systems specialist after thorough consultation on how we use Femme (long weekends and occasional week or two trips with the boat on a mooring in between.) I would only beef up amp hours if I moved aboard, maybe add more solar or wind charging . It has served us well for 13 seasons and I cannot recommend it enough.

p.s I am also a fan of the T-105's. Just check them once or twice a year for electrolyte levels and fill if needed. I just got my first replacement ones last year

[hilbert]

Ditto on what Paul wrote, well summarized.
A solar panel helps with the set it and forget it part and a battery monitor does gives peace of mind.

[Sea Hunt Video]

Matt, Maine Sail and all:

I have been following this thread with a lot of interest, trying to learn a little more about battery banks, charging, etc. Candidly, most of the posts went over my head (no surprise there ) until Maine Sail's most recent post referencing his article in Sailboatowners.com explaining the 2/Both/1/OFF switch. The article is excellent and written so that even someone at my level (Neanderthal ) was able to understand about 70% of Maine Sail's article.

Maine Sail - thanks very much As always, great stuff.

I am now trying to figure out how to copy it and print it so I can put in my reference binder onboard S/V Bali Ha'i.

[tjr818]

...I am now trying to figure out how to copy it and print it so I can put in my reference binder onboard S/V Bali Ha'i.

I am not sure of how one might do that on a PC, but on a MAC all you need to do is got to the top menu, click on "FILE", and then, click on "Export to PDF".

Maybe a PC user, or one of those super geek relatives can figure out how Bill Gates intended you guys to do it.

[mashenden]

WOW, this has been very educational - I really appreciate all of the expertise. It has helped me better define the end goal, and what I need to do in the interim. A few things I have learned along the way are:

• Contrary to what I initially thought, using the House bank to start the engine is NOT a terrible thing (but deep cycling a starting battery is). This point changed my prioritization on how I thought banks should be charged, which in turn made it possible to understand the concept of having both the charger and alternator attached directly to the House batteries, and maintaining the back-up Starter battery using something like an Echo.
• Starting a functional diesel engine does not take much battery power.
• I don't really know the condition of my House batteries. I believe that they were respectable (two Rolls/Surrette CH375 6v wet cells), but they have been abused (electrical fire before I owned the boat which inevitably shorted them, water got too low - my bad, probably nearer their end-of-life than not). I gravitated toward a 3rd bank because I need to add a fridge and do not have time to evaluate and possibly replace the House bank at this time. I now realize that designing my system around a short term vision was foolish. That said, I still need to add a fridge and I still do not have time to figure out the House battery unknowns. But I will now design the system for the long term thanks to everyone's input.
• Trying to automate the manual approach to switch/charge batteries is not ideal because it overlooks some fundamental issues related to charging and maintaining batteries. I am not going to pretend I took the time to understand all of it, but I did understand enough to realize that switching between banks to recharge (such as when manually doing the switching) is not an ideal approach.
• A LVD on the fridge is a good addition.
• Readily available 12V "Deep Cycle" batteries are crap.

I am leaning toward the design in the following diagram. It is designed around the wisdom presented in this post, and with a long term vision in mind (connecting fridge and chargers to the House batteries, maintain the Starter battery using a Echo, eliminating Bank 3).

I know this is what was presented much earlier but if I had not gone through the process of figuring out what things I thought were right, but really were not, then I would have been making "assumptions" that others were right, rather than knowing.

By connecting the fridge to the House bank, I can get a better feel for how strong/weak they are. If I find out that they are not strong enough to support the additional fridge load, I can always manually connect it to the Deep Cycle battery to get me home. It will serve for a short term back-up

Please comment if I missed any key points.

[mashenden]

I'd have to say that the fridge and supporting DC power changes that were discussed in this post were a tremendous success.

This weekend I did a 2 night cruise from Urbanna to Tangier Island (in the middle of the Chesapeake Bay) to Onancock (on the eastern shore of VA) and back to Urbanna. The fridge and power system did well, although as suspected, the house batteries are on their last legs. The house batteries were strong enough to run the fridge and electronics for about 10 hours, but they were then too weak to start the motor (I have not gotten used to my Victron 602 yet so not sure how low). The LVD is set to 12.1 v and it did not kick out so presumably there was still some juice left. I'll have to start researching battery prices.

Thank you for everyone's help.