1/BOTH/2/OFF Switches Thoughts & Musings

[Maine Sail]

I understand and posted that previously. The failure of the DCP is its lack of a dedicated B position. And both you and I prefer charging not go through any switch on a normal basis, only in case of an ACR or Echo failure.

The lack of a "common" or "C" post I suspect is what you mean??

They do have a dedicated BOTH/COMBINE position, see below. When you use COMBINE both banks become "combined", just as BOTH does. What you lose by using COMBINE on the DCP switch is the "start isolation". You lose start isolation because both switch output studs, house & start, are from one common bank and bingo in COMBINE, you are no longer "start isolated".. In COMBINE with the DCP both output studs are treated just as the "C" post is on a 1/2/BOTH is when it is in BOTH......

OFF/ON/COMBINE - COMBINE = BOTH

 

[Stu Jackson]

For Scott

For instance, I never indicated that I think it IS a good idea to set the switch on Combined for any reason other than to start the engine when one of the banks is in a discharged condition.

Scott, but that is exactly why I think it is not a good idea. The issue is simple: it is rarely the reserve bank that is discharged, it is the house bank, 'cuz that's the one you're using. The reserve bank, as Maine Sail and I and many others have been explaining for years, is almost always full. So, if your small reserve bank is connected to a large discharged house bank, the small reserve bank is going to discharge into the dead bank, leaving you with NOTHING. That is why it is not a good idea. Maine Sail described a situation just like that recently: http://forums.catalina.sailboatowners.com/showthread.php?p=848465&highlight=darn agm

This is a perfect example of what I mean by limited house loads.

As far as I can tell, when I turn the DCP switch On, it is no different than when you turn your switch to 1. If I ever turned my switch to Combined, it is no different than your switch if you turned it to B.

I agree. And I keep saying that the ONLY time one should use B is when charging sources are present. With a functioning echo charger, ACR, etc., you shouldn't ever have to use B, except for backup in case of ACR failure.

I understand that you can use 2 independently from 1, and I also understand that you may be saying that there is NEVER any circumstance where you turn your switch to B.

And that is a great advantage. You can use the reserve bank for LIMITED house loads, which the DCP simply can't do. And B, when charging sources are present, can be used to combine the banks if the ACR fails.

I am saying that I can only think of one reason to turn my switch to Combined and that would be for an emergency start. It seems to me that to say that is a no-no is a little nit-picky since the B position on your switch does the same thing and MS says that it is a common occurance, even with the 1-2-B switch.

No so, as far as I'm concerned. It's NOT nit-picky, it's a reality of operational use. If people don't know how to use their switches, they might consider wanting to learn more. The DCP can never be used as an "either-or" switch; they're either separated or combined. That is the biggest drawback, as Maine Sail's "Darn AGM" topic discusses in great detail. And I believe that this thread by Maine Sail discusses that the B position of the switch is (almost) never ever used.

I still feel the way I do about the DCP, but have also written that if you understand how a DCP works, you'll understand it's limitations. Many folks, for instance, like it because it separates the two banks and avoids potential electrical drop outs when starting the engine. Since both Maine Sail and I have posted the alternate switch diagrams to avoid this issue, we're saying there is more than one way to skin a cat.

The cat I would not like to see around is the one described in the link to Maine Sail's "Darn AGMs and DCP Switch" post. His client got zapped big time. Why put yourself or anyone else in that position?

That's all I'm sayin...

And I did a "Maine Sail-like" discussion about this here: http://c34.org/bbs/index.php/topic,6604.0.html

 

[mitiempo]

Let me rephrase.

With the DCP you are not able to start off the house bank except when both banks are combined - as with Both. You lose the ability to start with house bank alone, which a 1/2/both/off switch allows.

I have installed DCP switches but am not a fan for a cruiser - for a smaller sports fishing boat they make sense.

 

[Stu Jackson]

Brian, yes, that's the heart of the issue. And, as Maine Sail and I continue to say, using the house bank for everything including starting, is so much simpler and avoids ever draining one bad bank into a good one, like the link of his I posted above.

The DCP lacks the "either-or" advantages of the -1-2-B.

If you can't figure out how to use a switch on your boat, I suggest that there are a lot more complicated items on a sailboat that are a lot more challenging.

 

[mitiempo]

If you can't figure out how to use a switch on your boat, I suggest that there are a lot more complicated items on a sailboat that are a lot more challenging.

Very true.

 

[Maine Sail]

Brian, yes, that's the heart of the issue. And, as Maine Sail and I continue to say, using the house bank for everything including starting, is so much simpler and avoids ever draining one bad bank into a good one, like the link of his I posted above.

The DCP lacks the "either-or" advantages of the -1-2-B.

If you can't figure out how to use a switch on your boat, I suggest that there are a lot more complicated items on a sailboat that are a lot more challenging.

There is however a caveat to that bolded statement and Scott, I think, falls into that category. With a single battery house bank he will likely encounter electronic drop out. The DCP can be but one solution to stop that. His battery system is close to that of a center console or walk-around fishing boat so the DCP is not a "horrible" choice but one I would certainly walk a customer thought before "telling" them this is how it is going to be. when I explain the pro's & cons of a DCP to a cruiser they rarely if ever bite on it.

My customer with the AGM failure was TOLD that this is how it HAD to be when the boat yard was installing his new engine. He only realized the weakness of that system when he had a failure otherwise it was "easy"....

When you get to two or more batteries, as a house bank, PROPERLY WIRED and SIZED then starting on the house bank can work fine and drop outs will be very rare unless drawing the bank too deeply.

Of course the easiest solution, to me, if you already had a 1/2/B and have a small bank is to use position #1/HOUSE & add an ACR or Echo and then boot/start the electronics after you've fired up the motor.

Some don't want to do that so the DCP makes sense for them.. As long as a DCP owner is aware of how the switch operates that is all I care about. I find most DCP owners have not a clue as to what they gave up when they installed it. Most are only aware of the two benefits they gained, easy and start isolation....

 

[Scott T-Bird]

Thanks! I appreciate the comments ...

When I bought the switch a few years ago, I admit that I was interested in the start isolation and thought that it was reason enough to make the change. I considered that the ability to have two banks on simultaneously (start isolation) was a better choice than being able to have only one bank on or the other, but not both at the same time (unless combined). I always recognized that combining the banks was not desirable (notice how they color the Combined position in yellow with an exclamation!).

I did not consider the possibility that having the ability to switch from one bank to the other in isolation was a safety feature in the event of more signicant battery failures. I recognize the issue and am not dismissing it - it just isn't an issue for me at this time.

Actually, after last year's discussion on starting batteries, I simply made my two Group 27 batteries one bank for all needs and I don't have an auxillary bank at this time. So my switch is really just an On-Off switch in practice. I figure that if I were to add a starting battery, I would put it in the auxillary position and I would then have start isolation.

If I ever felt a need to have a true auxillary bank (instead of a start battery), I would then change out the switch - no big deal. That would only be likely if I was able to actually use the boat for cruising, which is something I still only aspire too!

Brian, I use the term "B" to represent Both, not bank 2. I sort of recognize the objection to combining the banks to simply start a 'dead' battery. The message that discharging a good battery into a dead battery is bad is understandable. I still don't see the real harm in combining batteries to simply get the engine started. Once it is started and batteries are charging, where is the harm? It seems like it is a common practice. I get it that you don't want to turn the engine off and then forget to change the selector.

It seems to me that the danger in combining batteries isn't in starting an engine when you have a dead battery but rather for other more serious battery failures as MS pointed out. I must be wrong, but the explanation hasn't been clear to me. I suppose that if you are trying to start the engine by combining a fully-charged single battery with a dead bank of larger batteries, you might not get it started. That doesn't seem like a circumstance that I have to worry about.

 

[Kettlewell]

Tremendous post!

Fantastic post--clearest explanation I have read anywhere. This should be required reading for anyone before they ask questions about battery switches.

 

[Kettlewell]

A couple of further thoughts on switches. I basically use this set up with the dedicated starting battery, but I put the single On/Off switch in the circuit from the House bank to the House loads, and I use the 1,2, Both switch to choose which bank starts the engine. I find this very intuitive. Come aboard, just flip the On/Off switch and everything on the boat is powered except for the engine starting circuit. Need to start the engine and I just turn the 1,2, Both switch to #1 normally (which I have marked "Start"). #2 is set up so that I can start on the House battery if needed. Both is obvious. I'm using a Trik-L-Start for maintaining the starting battery, and so far (one season) it has worked perfectly. To me it makes more sense to have the On/Off switch control the House loads--none of which are absolutely critical, but it is absolutely critical that you have some battery that can start the engine in an instant.

I paste a set of instructions next to the switches.

The two things I really like about having a dedicated starting battery are that I know the engine has plenty of juice no matter what to fire off when I need to in an emergency, and I don't get any voltage drop-off at the electronics, which I have experienced problems with. It is also much easier on the starter to always have high voltage and a fully charged battery. You can kill starters using a marginal battery.

Also, it is a remote possibility, but it is nice to be able to shut off juice to the engine in the case of a shorted solenoid or runaway starter, while still able to keep everything else running.

 

[Maine Sail]

A couple of further thoughts on switches. I basically use this set up with the dedicated starting battery, but I put the single On/Off switch in the circuit from the House bank to the House loads, and I use the 1,2, Both switch to choose which bank starts the engine. I find this very intuitive. Come aboard, just flip the On/Off switch and everything on the boat is powered except for the engine starting circuit. Need to start the engine and I just turn the 1,2, Both switch to #1 normally (which I have marked "Start"). #2 is set up so that I can start on the House battery if needed. Both is obvious. I'm using a Trik-L-Start for maintaining the starting battery, and so far (one season) it has worked perfectly. To me it makes more sense to have the On/Off switch control the House loads--none of which are absolutely critical, but it is absolutely critical that you have some battery that can start the engine in an instant.

I paste a set of instructions next to the switches.

The two things I really like about having a dedicated starting battery are that I know the engine has plenty of juice no matter what to fire off when I need to in an emergency, and I don't get any voltage drop-off at the electronics, which I have experienced problems with. It is also much easier on the starter to always have high voltage and a fully charged battery. You can kill starters using a marginal battery.

Also, it is a remote possibility, but it is nice to be able to shut off juice to the engine in the case of a shorted solenoid or runaway starter, while still able to keep everything else running.

This diagram does a very similar thing...

1/2/BOTH to #1 = House
ON/OFF to ON = Dedicated Start Battery

You still have the ability to start and run house loads of either bank, 100% isolate a bank if necessary, and have full start isolation.

I don't get any voltage drop-off at the electronics, which I have experienced problems with. It is also much easier on the starter to always have high voltage and a fully charged battery. You can kill starters using a marginal battery.

Compared to most single battery "starting banks" a decent sized house bank on a cruising boat, even at 50% depleted, usually has a lot more current and often less voltage drop than the starter battery does.

I have measured this on numerous boats and at varying levels of discharge. Of course starting on the HOUSE means you MUST be practicing good battery care and not deeply discharging the house bank. It also requires PROPER wiring and wire gauges of the correct size. Our house bank even at 50% SOC still has more available CA than does our single "start battery". It even holds a higher voltage, more than enough to avoid drop out, under starting loads all the way down to 55% SOC which is as far as I've measured it. On boats with suspect wiring, connections or house banks that are "marginal" I usually suggest starting off a dedicated starting battery.

Having been starting on house banks for the better part of 20 years I know it works well when properly done, "properly done" being a key qualifier.... Undersized wiring is likely a bigger contributor to killing starters than voltage dip on a large house bank as the wires voltage drop gets stacked on top of the banks voltage dip. I have never had a starter failure though I replace plenty of starters on boats that are wired with toy wire such as #4GA or where the terminations are poor...

Our "starter battery" at 100% SOC drops to 10.3V..

Our house bank drops to 11.7V. Which one is putting less voltage & current to the starter..?

 

[Kettlewell]

MaineSail, makes sense as long as your house bank has a decent charge, but I have stupidly discharged a house bank way down many times to the point it wouldn't even turn over the engine and I don't like the idea of having to switch batteries in the middle of the night to get the engine going. Yes, that is not good battery management on my part, but it has happened and it is nice to be able to recover. Also, my boat is frequently left with less experienced crew onboard and I like to have the switching as simple as possible. In other words, even if the house battery is run down it doesn't require any switching to start the engine. Your diagram here with the dedicated start battery does that and you get no voltage drop-off at the electronics if they are connected to the house bank.

 

[GWilliams]

Do the batteries charge from shore power and if so do you leave the switch to both or can it be turned off and still charge the batteries from shore power. I have a Catalina 27 recently purchase and I assume standard wiring. How can I easily tell which is the starting battery and which is the house?

 

[Dantodd]

Awesome thread. I joined SBO just for this thread!

I have three battery banks and three on/off switches. The boat came equipped with 2 on/off switches and I added a third. (it also has a ground disconnect or "all off" switch)

Bank 1: 400 ah main house (brand new "Costco "golf cart" batteries, being installed later this week)
Bank 2: 220 ah reserve house (5 year old, but never before installed T-105's)
Bank 3: group 27 "maintenance-free" flooded cell starter (50hp 4JH series Yanmar)

The starter is not interfaced with the house banks at all.

The house switches are wired with a just a jumper creating a "C" post as a 1/B/2/Off switch would have.

I currently run a diode isolator from the alternator and a 3-stage, 3 circuit Sentry charger off the mains to each bank.

I am now wondering if I should replace the 2 T-105s with Costco batteries and create a single house bank. Then I would have.

Switch 1: house bank (600 ah)
Switch 2: starter
Switch 3: emergency interconnect

And then install an ACR or Echo Charger for alternator charging purposes.

Alternatively, can I run parallel ACRs or Echo chargers off the house bank? I really like having multiple house banks. The only real issue I have with the current setup is not being able to use the house bank to start the engine should my starter battery fail, with no load on it I don't see that as a very likely scenario.

Finally, I could hardware my starter battery and use the current starter switch as an emergency interconnect. The only problem with that is I wouldn't have an easy disconnect for a stuck starter solenoid.

After following some of the commentary on the Echo I am not clear on what happens when I run my mains charger. If the house bank is getting a high voltage charge from my charger while the starter is floating will the Exho feed more voltage to my starter battery thus eliminating the value of having a multi-circuit mains charger? It seems that the Echo would force the starter to take whatever voltage house bank is getting (less a minimal V drop) while this may not be terrible for my current battery what if I replace the current starter battery with a gel cell or AGM?

So. One house bank or two? If you can only have one do you have a starter disconnect or an emergency interconnect? ACR(s), Echo Chargers, or one of each?

Thanks for the great resource. I'm in the parking lot of the marina getting ready to head down to the boat, a wiring schematic is on today's agenda.

 

[mitiempo]

Dan

It will be more efficient and the batteries will last longer in one large bank. There is nothing to be gained with multiple house banks.

The start battery needs a disconnect.

You can wire either to parallel the banks in an emergency or to use the house alone for starting.

Commonly if using an Echo Charge all charging sources go direct to the house bank, the Echo feeding the start. Your charger most likely just divides its amperage among the banks anyway, if it goes only to the house bank it will be putting its output where it is needed most. But either way the Echo will not give the start battery more than it senses it needs. The only thing that forces a battery to accept current is voltage. Either an Echo or an ACR, not one of each.

A good battery monitor like the Victron BMV-600 would be a good addition as well if you do not currently have one.

 

[Dantodd]

It will be more efficient and the batteries will last longer in one large bank. There is nothing to be gained with multiple house banks.

why more efficient? I'd hate to waste half or more of the life of the 2 existing T-105s. Is it better to just recycle them and replace with Costco GC2s or are you suggesting a mixed bank?

The start battery needs a disconnect.

I agree.

You can wire either to parallel the banks in an emergency or to use the house alone for starting.

I think I like the idea of using the starting battery to start (generally) and then wiring to interconnect only when necessary. I think there's a better chance of hearing some hesitation in the starting battery and maybe catching it before complete failure this way.

Commonly if using an Echo Charge all charging sources go direct to the house bank, the Echo feeding the start. Your charger most likely just divides its amperage among the banks anyway, if it goes only to the house bank it will be putting its output where it is needed most.

Doesn't this sort of defeat the entire purpose of having a multi-bank mains charger? I could be mistaken but I don't believe my Sentry simply splits up the amperage amongst the batteries, if I remember correctly it can be adjusted to feed different voltages to the various banks in the event you are using different battery types in the different banks.

But either way the Echo will not give the start battery more than it senses it needs. The only thing that forces a battery to accept current is voltage. Either an Echo or an ACR, not one of each.

I thought the echo didn't sense the state of charge of the secondary bank and merely passed through the voltage it rec'd from the charger/house bank with a slight drop. I thought I read that on one of the numerous Echo threads here. If I retain 3 banks I don't believe I can keep them all separated and still charge them with only one ACR or Echo charger.

A good battery monitor like the Victron BMV-600 would be a good addition as well if you do not currently have one.

I don't and I do plan on installing one.

 

[Kettlewell]

I too would vote for one large house bank, and one start battery, with all the charging sources going to the house bank and the EchoCharge taking care of whatever charging the start battery requires. Using your three switches you can set it up to start either off of the house or the start or you can combine the banks if you want to, which you would usually only do for charging if the EchoCharge were to fail for some reason. The larger the single house bank the less the depth of daily discharge and the greater its life.

 

[mitiempo]

Dan

A larger bank is always more efficient than 2 banks that total the same AH and your batteries will last longer as they will be drawn down less than if using a smaller bank. I would not suggest a mixed bank though.

I do recommend a dedicated starting battery. Ideallyou can wire it to allow starting from the house bank alone if there is a problem with the start battery. This is always preferred to combining a charged bank with a one that is not charged. The only reason to combine both banks is if the ACR or Echo fails.

If your charger has totally separate outputs (I would confirm this) you can wire it to each bank. But any other charging - alternator and solar or wind now or in the future can go direct to the house bank. The ACR or Echo would have no effect on shore power but certainly would if using the engine.

The Echo Charge passes up to 15 amps of current to the start battery if it is needed. It does sense the battery which will not be overcharged. If an ACR is used the banks are paralleled when a charging voltage is sensed.

You are correct, if you keep 3 banks a single Echo or ACR will not work. Another reason to have only 2 banks. Not only is one house bank more efficient, but there is absolutely no advantage to having multiple house banks.

 

[Maine Sail]

Some thoughts.

1- Go to one large house bank. Shallower discharges lead to longer bank life and with a bigger bank you'll be drawing it down less as a % of discharge and the bank will last longer. Not only that you can actually get more Ah's out of a larger bank when compared with the same load than you can on a smaller bank due to Peukert effect.

See this thread: Effect of Current on Ah Capacity

2- By doing this you can keep your three On/Off switches, one dedicated for starting, one for house and one as an emergency combine, or to allocate either bank to doing both start & house if necessary. To make the START do everything turn OFF the HOUSE switch and turn ON the emergency switch. The reverse works too. This only works if the emergency switch is connected to the load side of the HOUSE & START On/Off switches.

3- If you want a true multi-stage battery to battery charger then the Sterling B2B's are great. The Echo will not overcharge a second bank and it is a great unit. It has a capped max voltage output of 14.4V, below the "gassing level", but you'll rarely see that. Unless your equalizing your house bank don't expect 14.4V out of the Echo. As for the current the battery limits it, and decides what it will accept, not the charger or Echo Charger.

4- The Sentry chargers are ferro chargers that shut off so they don't cook the batteries. This was a major problem with ferro-resonant chargers and is why almost no-one is using that technology in chargers any longer. Many chargers have "multiple outputs" but all batteries get the same charge algorithm/voltage. There are some chargers with two internal chargers but they are rather rare and expensive...

 

[Ron20324]

3 switches: Beneteau

I have three battery banks and three on/off switches. The boat came equipped with 2 on/off switches and I added a third.>>> I am now wondering if I should replace the 2 T-105s with Costco batteries and create a single house bank. Then I would have.

Dan, I have the setup you have- one switch for each of 3 batteries. The Xantres charger has one output to each of the three batteries. I wired my alt and the starter to that common "buss" wired between the 3 switches. This way, you can switch on ANY of the three batteries to start, and you can not run the alt without a battery on line for the starter. Since you already have the (new?) 2x6s and space enough for them, go ahead and use them.

I have 2 x 31, and a 24 which WAS the start battery. I intend to go to 3 x 31s and just rotate their usage, using any two as the working house bank.

 

[Dantodd]

Some thoughts.

1- Go to one large house bank. Shallower discharges lead to longer bank life and with a bigger bank you'll be drawing it down less as a % of discharge and the bank will last longer. Not only that you can actually get more Ah's out of a larger bank when compared with the same load than you can on a smaller bank due to Peukert effect.

See this thread: Effect of Current on Ah Capacity

I understand the value of a larger house bank. The question is not 625ah in a single bank vs. 2 banks. The options are one 400ah bank or one 400 ah bank AND one 225 ah bank. Unless I put two older T-105s in || with my 4 Costco GC2s.) Frankly, I spec'd the banks for cruising which is no longer on the table and 400 ah is plenty for weekend+ cruising/mooring in the SF Bay and should be adequate for passages down to LA/SD.

2- By doing this you can keep your three On/Off switches, one dedicated for starting, one for house and one as an emergency combine, or to allocate either bank to doing both start & house if necessary. To make the START do everything turn OFF the HOUSE switch and turn ON the emergency switch. The reverse works too. This only works if the emergency switch is connected to the load side of the HOUSE & START On/Off switches.

This is my plan if I go to a single house. Though the post by Ron reminds me that I do have a "general" switch too, so I do have 4 physical battery switches but using all 4 would mean losing the ability to break the ground connection. I'm not sure of the importance of that though.

3- If you want a true multi-stage battery to battery charger then the Sterling B2B's are great. The Echo will not overcharge a second bank and it is a great unit. It has a capped max voltage output of 14.4V, below the "gassing level", but you'll rarely see that. Unless your equalizing your house bank don't expect 14.4V out of the Echo. As for the current the battery limits it, and decides what it will accept, not the charger or Echo Charger.

Good to know that exists but I am on some budget and based on what You've said and the other EchoCharger discussion I dug up I'll go that route.

4- The Sentry chargers are ferro chargers that shut off so they don't cook the batteries. This was a major problem with ferro-resonant chargers and is why almost no-one is using that technology in chargers any longer. Many chargers have "multiple outputs" but all batteries get the same charge algorithm/voltage. There are some chargers with two internal chargers but they are rather rare and expensive...

Yes, I just read the Sentry manual again. Even the older G series have the shut-off which is good. I am not sure why I thought it was different actual charge circuits, the manual was clear that each battery gets the same charge, the only purpose of the separate outputs is battery isolation. It sure seems that it would be both simple and a great tools for boaters to build a single charger that will work off of either the mains OR alternator/solar. Then you could just install a single charger and all of the isolation/combining/charging would be done automatically. That would relegate all switch use to selection only.

So, I will need to buy a battery monitor and an EchoCharge. But the actual bank configuration is still up in the air.

A) Single 400ah house and a G27 starter

B) Two house banks, (400ah + 225ah) and a G27 starter but losing the ability to switch battery ground.

C) As in B but with the 225ah bank being a true emergency bank needing cable moving to make active thus leaving the ground disconnect in situ.

D) Replacing 2 good T-105s (very low WAF) and making a single 600ah house bank. Economically this would mean not buying a battery monitor for this season.