Best wiring for battery switch

Stu Jackson · May 1, 2012

Phil,

You might be interested in these (the topic and the links within it):

http://c34.org/bbs/index.php/topic,6911.0.html

Somethin' new everyday.

Sumner · May 1, 2012

Phil P said:
My newly acquired 91 Hunter 375 has both a 12-volt starter battery and two 6-volt house batteries. All are brand new. The Perko battery switch has positions for "All", 1 & 2. Power only works if "all" or "1" is selected. When switched to "2", nothing seems to work and the voltmeter at the nav station reads zero. From this I imply that either the house bank is somehow connected to nothing, or all the batteries are in parallel (6 volt in series). The owners manual is a joke.

As a new boat owner, I would assume that 1 connects to the starter battery and two connects to the house bank and All connects to all three. Is this correct?

I'll take a guess that the starter battery might be wired direct to the starter to avoid damaging the alternator if the switch was switched to "off" while running. The switch might just be controlling the house bank and a potential second house bank that was never installed. You really just need to trace the wiring to figure it out as there are two many options and we will all just be guessing.

Our Endeavour has two switches. The first one selects if the starter is getting juice from the starter battery or from the second switch or both. The second switch selects one house bank or the other or both.

The alternator has 2 outputs and one goes directly to the starter battery and is always connected and the second goes to one of the house banks and is always connected to that battery bank (2 six volt batteries). I'm going to remove the wire from the alternator going to the house bank and bridge the two alternator outputs together and take the new single bridged output to only the starter battery. Then I'll use a combiner between the starter battery and the house banks. This will now combine the batteries if they are getting charge from the alternator or from the solar array. The solar array will be connected to the output of the second switch. It won't hurt the charge controller or solar array we have if they aren't connected to a battery, but we will probably have the switch in "both" 100% of the time to use and recharge both house banks simultaneously.

Trace your alternator and main battery wires. It won't take long,

Sum

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Stu Jackson · May 1, 2012

Sumner said:
I'm going remove the wire from the alternator going to the house bank and bridge the two alternator outputs together and take the new single bridged output to only the starter battery and then use a combiner between that battery and the house banks. This will now combine the batteries if they are getting charge from the alternator or from the solar array that will be connected to the output of the second switch. It won't be hurt if it isn't connected to a battery, but we will probably have the switch in "both" 100% of the time to use and recharge both house banks simultaneously.

Sum,

You might want to reconsider that. The Yandina combiner literature clearly says to run the AO to the house bank, at least my WM model did. http://www.yandina.com/acrobats/C150Data.pdf

The reason is to LIMIT the amount of current that needs to flow through the combiner as much as possible. The start bank is almost always full, so run the AO to the house bank, and use the combiner to the start bank.

The use of B on the switch, with a combiner, should be discouraged. That's what the combiner is there for.

As Maine Sail and i have been saying, only use B if your combiner or echo charger or ACR breaks and only when charging sources are present.

All charging sources should go to the house bank and let the combiner do its thing.

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html [added 9/21/11]

[added 1/31/2012] This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

...unless I'm missing something...

Stu

Sumner · May 1, 2012

Stu Jackson said:
Sum,

You might want to reconsider that. The Yandina combiner literature clearly says to run the AO to the house bank, at least my WM model did. http://www.yandina.com/acrobats/C150Data.pdf

The reason is to LIMIT the amount of current that needs to flow through the combiner as much as possible. The start bank is almost always full, so run the AO to the house bank, and use the combiner to the start bank.

The use of B on the switch, with a combiner, should be discouraged. That's what the combiner is there for.

As Maine Sail and i have been saying, only use B if your combiner or echo charger or ACR breaks and only when charging sources are present.

All charging sources should go to the house bank and let the combiner do its thing.

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html [added 9/21/11]

[added 1/31/2012] This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

...unless I'm missing something...

Stu

I agree with what you are saying for most cases, but we have about 500 watts of solar and don't move all that much with the motor and anchor a lot, so probably over 90% of our charging capabilities will be solar without running the diesel that much most days or for sometimes days at a time. Kind of think of our system as backwards from what most people do that run the diesel for an hour or two each day to charge the house bank.

Also we have two sets of 6 volt batteries in the house bank, so those will be combined with the one switch and the second switch that can combine the house bank to the start battery will remain open and the combiner will be use between the house banks and start battery as you suggested. We would only use the switch between the house banks and the start battery if it was dead as you don't want the starting current running through the combiner as I'm sure you know.

Also we are using a Blue Sea's ARC and the wiring diagram there looks like it will be fine for what we are doing. They do mention though that if you are charging primarily with an alternator that it is usually best to run it to the house bank as you suggested and combine to the start battery.

I suggest that the majority of those out there that don't have a large solar array or a separate gen-set wire like what you are saying. Since our situation is different I probably shouldn't of mentioned it and muddied the waters,

Sum

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Maine Sail · May 1, 2012

Sumner said:
I agree with what you are saying for most cases, but we have about 500 watts of solar and don't move all that much with the motor and anchor a lot, so probably over 90% of our charging capabilities will be solar without running the diesel that much most days or for sometimes days at a time. Kind of think of our system as backwards from what most people do that run the diesel for an hour or two each day to charge the house bank.

Also we have two sets of 6 volt batteries in the house bank, so those will be combined with the one switch and the second switch that can combine the house bank to the start battery will remain open and the combiner will be use between the house banks and start battery as you suggested. We would only use the switch between the house banks and the start battery if it was dead as you don't want the starting current running through the combiner as I'm sure you know.

Also we are using a Blue Sea's ARC and the wiring diagram there looks like it will be fine for what we are doing. They do mention though that if you are charging primarily with an alternator that it is usually best to run it to the house bank as you suggested and combine to the start battery.

I suggest that the majority of those out there that don't have a large solar array or a separate gen-set wire like what you are saying. Since our situation is different I probably shouldn't of mentioned it and muddied the waters,

Sum

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Sum,

With 450 Ah's of house bank you'll want the alt to go direct to the larger bank. If not you will get into a relay cycling issue. Blue Seas recommends this when banks are of unequal size. Their basic diagram is fine of your banks are close to equal size but two 6V banks can be 225Ah or 450Ah depending upon switch location.

Good move on jumpering the dual output alt, those were nothing but trouble. and lots of banks were cooked due to them.

But hey you don't have to take my word, or Stu's, Blue Sea has a nice technical brief on this subject. This is one of the most common fixes I have to do on ACR's..

From Blue Sea:
"A simple solution for boats with a large House battery bank and a relatively small Start battery bank, including many sailboats, is to connect the charging source to the House battery bank (see wiring diagram). This solution works because the Start battery bank is typically smaller and less discharged than the larger House battery bank. When the battery banks are combined for charging, there isn't a significant drain to lower the system voltage to the disconnect level. "

Sumner · May 1, 2012

Maine Sail said:
Sum,

With 450 Ah's of house bank you'll want the alt to go direct to the larger bank. If not you will get into a relay cycling issue. Blue Seas recommends this when banks are of unequal size. Their basic diagram is fine of your banks are close to equal size but two 6V banks can be 225Ah or 450Ah depending upon switch location.

Good move on jumpering the dual output alt, those were nothing but trouble. and lots of banks were cooked due to them.

Ok, I'm trying to understand this and it wouldn't be hard to put the alternator to the house bank, but if I did that I'd want it going to one of the 2 sets of batteries either at the pos. post on one set or at the back of the switch where the pos. cable attaches so that there would be no chance of the alternator not being connected to a battery regardless of switch position. One of the two alternator outputs was wired in that manner.

Here is a quote from the Blue Sea's instructions...

Open/Close Cycling
• If your electrical system is configured with a charging source that cannot supply the full load current
being drawn from the receiving battery, an open/close cycling process can occur. If this cycling
continues, the second battery bank could eventually discharge even though a charge source
is present.

Is this what you are referring to? If so I'm not seeing where we would get into the situation above, but I don't think I entirely understand what they are trying to say either?

We have no high inverter loads on the boat. Everything is 12 DC and the frig at about 4-5 amps is the largest draw. I think from trips on the Mac that we are using about 50-60 amp/hr a day. We will stay with the 4 six volt batteries mainly to have enough power to get us through 2-4 days of bad solar.

Any added input is welcome,

Sum

P.S. Move this to a new thread if you want as we are straying from the original post, but I like the info.

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Maine Sail · May 1, 2012

Sumner said:
Ok, I'm trying to understand this and it wouldn't be hard to put the alternator to the house bank, but if I did that I'd want it going to one of the 2 sets of batteries either at the pos. post on one set or at the back of the switch where the pos. cable attaches so that there would be no chance of the alternator not being connected to a battery regardless of switch position. One of the two alternator outputs was wired in that manner.

Here is a quote from the Blue Sea's instructions...

Is this what you are referring to? If so I'm not seeing where we would get into the situation above, but I don't think I entirely understand what they are trying to say either?

We have no high inverter loads on the boat. Everything is 12 DC and the frig at about 4-5 amps is the largest draw. I think from trips on the Mac that we are using about 50-60 amp/hr a day. We will stay with the 4 six volt batteries mainly to have enough power to get us through 2-4 days of bad solar.

Any added input is welcome,

Sum

P.S. Move this to a new thread if you want as we are straying from the original post, but I like the info.

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Sum,

#1 There is no benefit to wiring to the start battery only the potential for issues. If you are concerned about starting loads then use the SI (start isolation) feature those relays have. A simple wire to the starter circuit disengages the relay during starting.

#2 I would not wire the two 6V house banks as two 6V house banks. I would wire them in series parallel so you can charge them properly and connect your load and neg so you keep the bank charging "balanced".. Also throwing a switch in there makes using any sort of battery monitor on that bank quite difficult. Even if you plan to always have it on BOTH I am still not a fan of that set up. More connections and makes monitoring and bank balance very difficult.

Sumner · May 1, 2012

Maine Sail said:
..
Good move on jumpering the dual output alt, those were nothing but trouble. and lots of banks were cooked due to them.

Maybe that is why the batteries were shot on the Endeavour when we got her?

Maine Sail said:
....
From Blue Sea:
"A simple solution for boats with a large House battery bank and a relatively small Start battery bank, including many sailboats, is to connect the charging source to the House battery bank (see wiring diagram). This solution works because the Start battery bank is typically smaller and less discharged than the larger House battery bank. When the battery banks are combined for charging, there isn't a significant drain to lower the system voltage to the disconnect level. "

I didn't see the above earlier. The above is why I want the solar to go to the house bank as that will be our primary charging mode, but I'll move the alternator output there if it will help when we are motoring.

Thanks,

Sum

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Sumner · May 1, 2012

Maine Sail said:
#2 I would not wire the two 6V house banks as two 6V house banks. I would wire them in series parallel so you can charge them properly and connect your load and neg so you keep the bank charging "balanced".. Also throwing a switch in there makes using any sort of battery monitor on that bank quite difficult. Even if you plan to always have it on BOTH I am still not a fan of that set up. More connections and makes monitoring and bank balance very difficult.

Are you saying just hard wire the two 6 volt banks parallel to each other and not use the "both" on the switch? Then if we had a problem just un-wire one bank? I could do that as we will have them tied together all of the time with the switch.

We are on the boat now in the yard doing all of this.

Maine Sail said:
... A simple wire to the starter circuit disengages the relay during starting..

I'm doing that although I don't think it is necessary for our loads.

Thanks,

Sum

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Maine Sail · May 1, 2012

Sumner said:
Are you saying just hard wire the two 6 volt banks parallel to each other and not use the "both" on the switch?

Yes..

Sumner said:
Then if we had a problem just un-wire one bank? I could do that as we will have them tied together all of the time with the switch.

We are on the boat now in the yard doing all of this.

Much better for keeping the banks balanced and you lose some connections too. If you have an "issue" diagnose and take the individual batteries off line manually. Leave enough room in the neg lead to do this...

Best wiring to keep 4 6V balanced is below. The DC neg and pos system leads should be opposite each other and no other + or - leads taken off the battery bank other than those points. All charge sources should also be connected as shown. Pulling off the "GND NO" side leave you with an unbalanced bank as all the energy, charging and discharging, wants to use the first "battery" (technically two). What you'll see after a while with the "GND NO" wiring is that the first two batts are really suffering because they've seen more use and the other two are in better shape but now we have an unbalanced bank and it begins to snow ball and get worse and worse.

Sumner said:
I'm doing that although I don't think it is necessary for our loads.

If you wire the alt to the house bank or the start bank and have solar the relay will be engaged even with the engine off. For most boats this is not the case. This means when you start the motor the high in-rush to the starter will be pulled across the ACR relay. Even if your start battery is full and directly connected to the starter the house bank will still try to keep the voltage up during starting, and the resulting current will flow through the relay and this can potentially harm the relay..

Sumner · May 1, 2012

I've seen that before, thanks. I'll do that and I'll be sure and wire the start sense wire to the ARC also,

Sum

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Stu Jackson · May 1, 2012

Sum, your"situation" is NOT that unusual, but it seems you are making it more complicated than it needs to be.

KISS: ALL charging sources go to your house bank; make the house bank as BIG as it can be (why? 'cuz with the very same daily drawdown the % of your battery capacity used will be less even with the same amount of lead sitting there on your boat!); use the ACR properly as we have described. Use your 1-2-B switch between the start and house banks, not to separate your house bank (like the diagrams in the links we provided).

Regardless of whether you use your engine not at all or a lot, this is the preferred way to set up charging systems.

I know I gave you a lot to read, but review it a few more times. It took me a looong time to figure it out, and MS kinda beat me to it or at least I paralleled (PI!) his thinking (east coast, west coast, all around the town!

)

Sumner said:
I've seen that before, thanks. I'll do that and I'll be sure and wire the start sense wire to the ARC also,

What is a start sense wire? If you mean battery sense wire from an external regulator, it should go to the house bank, too.

Dantodd · May 1, 2012

Sumner,

I just went through all of this with my boat as well. Pay attention to the way the pos and negative leads come off the bank. I did it wrong the first time and while I was getting a good 12 v from the bank when I disconnected everything and let the batteries rest there was a considerable difference in state of charge between the various batteries. After properly connecting the leads the batteries are much more closely matched when I check them. I have no idea why as it seems that it shouldn't matter since the parallel jumpers should make one battery just as good as the next but it doesn't.

Also, using all of your house batteries as a single bank gives you more usable amp hours. This is due to Peukert's Law which, in short says that the smaller the load is compared to the total capacity of a battery the longer that load can be supplied. Since the 225Ah rating is based on a 20 hour load that means the battery is rated for 225Ah with an 11.25amp load (225/20) but if your load is only 5amps then you will get greater than 225Ah from the battery. This means that you get more than double the usable electricity from a bank that is twice as large. (or by converting from 2 house banks to 1)

However; having only one house bank requires better monitoring of its status to prevent excessive draining since you can't just flip over to the secondary bank and then charge when convenient. This is why I bought a battery monitor, the Victron BMV-600. Maine Sail has a great how-to in his signature so check it out. If you use the monitor as a guide for charging and maintenance it will certainly pay for itself ($150) by the life extension it provides just to your first set of batteries.

Sumner · May 2, 2012

Stu Jackson said:
..What is a start sense wire? If you mean battery sense wire from an external regulator, it should go to the house bank, too.

It is the wire MS mentioned that disables the ARC while starting. I'm running it and the charge sense wire will go to the house bank and it is under 10 feet

.

Also we have had our 2 batteries on the Mac in parallel as one bank all along for the reasons that have been stated. We use and charge them together. I always planned on the same situation with the 2 six volt banks the Endeavour has but I was going to parallel them with the switch. Now I'll wire them in parallel without the switch as per MS's diagram. I'll move the alternator lead to the house bank and wire the ARC as per Blue Sea's instructions.

Thanks guys and now does anyone have any advice for poor Phil that started this thread and Phil I apologize for it drifting off track onto my situation,

Sum

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