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Old 16-09-2014, 12:34   #1
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Building a 3 Bank System, need help Bigtime

Hello all! I've found myself overwhelmed so I'm turning to the trusty CruisersForum for help. The 7 month trip starts in 7 weeks and I need to build my battery banks. I'll try to keep it short, but theres a lot of info. Thanks in advance for your time!

Currently, my 1970 Morgan 38 is running off of two 12v batteries serving as starting and house banks. A 2 bank switch running to the engine and the 12v panel. There is not any AC power on the boat (except for extension cords running inside when Im plugged into the dock!). My battery charger is a Readi-Amp 8 old school battery charger. Everything from the power inlet up to the 12v panel is being rebuilt.

The Goal is to set up a 3 battery bank system with batteries I've just bought for this purpose: Six 6v Trojans and 2wo 12v group 27s. The plan is to build two house banks with the Trojans (one with 2 Trojans and the other with 4) and one dedicated Starting Bank with the two group 27s.

I'll have my current 2 bank switch (Batt 1, Batt 2, All, Off) set to run the house banks and lead to the 12v panel (we dont and likely wont have any large installed inverters) and a new On Off switch for the 12v starting bank. I will have an AC breaker and a panel to give me a few outlets while I am on shore power, so no more extension cords for me!

One big question is how to wire the system including the battery charger (in hand), the charge controller, the solar panels, and possibly a wind generator as well. How would the alternator fit into this system if I want it to be able to charge all banks and not just the starting bank? would the Alt run to the charge controller and the starting bank just run through the On/Off switch to the starter?

Many other questions Is it even wise to run two 12v batteries in parallel to start the engine? Is simply having an On/Off switch the right idea for this dedicated starting bank? Where should I be concerned with adding fuses and grounding the system in addition to grounding on the engine etc?

If someone could help me get a visual idea for how this will work out, I'll be much better off. Im no electrician, so this is all one big learning curve for me. And boy do I seriously appreciate the help!
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Old 16-09-2014, 13:58   #2
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Re: Building a 3 bank system, need help bigtime

Why three banks? Since you have already bought the batteries I'd do two banks, one with the Trojans and the other with the 12v's. If it's not too late to take the 12v's back and exchange them for more Trojan's, I would.
I see the logic of two of the same banks and alternating use between the two, other will tell you that you only need one bank, but three?
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Old 16-09-2014, 14:07   #3
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Re: Building a 3 bank system, need help bigtime

Yes - why three banks? Adds complexity and reduces capacity.


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Old 16-09-2014, 14:16   #4
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Re: Building a 3 bank system, need help bigtime

Scale back a little bit. Put all 6 trojans in series parrallel to make 1 bank. Return one of the Group 27's and use that money to buy a balmar duo charger. Hook the duo charger from the trojans to the group 27. Now any time the trojans are getting charged the 27 will be getting charged up to i believe 15 amps.

As far as the 1/2/both/off switch hook the trojans to 1, the group 27 to 2 and then have your controller and regulator all go to the trojans.

Now this leaves you with a bigger house bank that can also start the engines with. Essentially as long as you never "kill" the trojans you can run your house loads and start the engine with it. Only leave your group 27 as an emergency engine starting battery (think of it like a permanent back up jumper box to start your engine with should things go bad)

The nice thing with this is you can essentially set the switch to 1 and then forget it. you never have to worry about switching back and forth to start the engine unless you have a problem with the Trojans and then you switch to 2 to start the engine
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Old 16-09-2014, 14:26   #5
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Re: Building a 3 bank system, need help bigtime

H-
Modern logic is to have one large house bank, because that way you can get "the same" amount of power while drawing it down only q/2 as much as each of two banks. And that gives you longer battery life and more charge cycles.
Then, use a West Combiner or EchoCharger to automatically combine the house and starting batteries once charging begins. Manual switch strictly as a backup and cut-off. I can't see why you'd need more than one Group27 as a starting battery unless the engine was in bad shape and particularly hard to start, so I'd also suggest ditching one of those.
As to how to wire all the stuff...that would depend on the exact list of stuff and I think you'll find other threads showing many of the options and considerations for that.
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Old 16-09-2014, 14:29   #6
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Re: Building a 3 bank system, need help bigtime

Quote:
Originally Posted by ontherocks83 View Post
Scale back a little bit. Put all 6 trojans in series parrallel to make 1 bank. Return one of the Group 27's and use that money to buy a balmar duo charger. Hook the duo charger from the trojans to the group 27. Now any time the trojans are getting charged the 27 will be getting charged up to i believe 15 amps.

As far as the 1/2/both/off switch hook the trojans to 1, the group 27 to 2 and then have your controller and regulator all go to the trojans.

Now this leaves you with a bigger house bank that can also start the batteries. Essentially as long as you never "kill" the trojans you can run your house loads and start the engine with it. Only leave your group 27 as an emergency engine starting battery (think of it like a permanent back up jumper box to start your engine with should things go bad)

The nice thing with this is you can essentially set the switch to 1 and then forget it. you never have to worry about switching back and forth to start the engine unless you have a problem with the Trojans and then you switch to 2 to start the engine


sounds like what we have done, except, our charging Balmar, solar, and wind, go to one bank of (10 ea 4ds) our starter battery is kept "warm" with a small stand alone solar panel.
My batteries, (lifeline AGM) are rated at 12.8 fully charged, 12.2 is 50% and our house bank has never dropped below 12.6.. We equalize every 6 months or so...
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Old 16-09-2014, 15:10   #7
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Re: Building a 3 bank system, need help bigtime

And the winner is.......

A three way between posts 3, 4 and 5.

One house bank is
1. simpler
2. better for battery health

So take all the Trojans and wire series/parallel for one house bank.

Starting bank - one group 27 should be fine. That's all I'm using for my 60 HP Westerbeke.

AND, get the Echocharge or similar to keep the start batter automatically charged but also automatically isolated from the house bank so you don't accidentally run it down.

Do a search for battery wiring diagram from Mainesail or Stu Jackson who have both posted excellent, well drawn and easy to follow wiring diagrams to do all the above.
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Old 16-09-2014, 15:14   #8
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Re: Building a 3 bank system, need help bigtime

Click on this link for a previous thread that will include a very basic, most simple wiring diagram and if you click on the links in Stu Jackson's post #2 better but slightly more complex versions.

Two-switch Battery Scheme
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Old 16-09-2014, 15:28   #9
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Re: Building a 3 bank system, need help bigtime

I agree with the others to simplify and combine all the 6V, in a 3x2 configuration, into one bank. If one group 27 will satisfy the cranking amp requirements for your engine, use that as a starting battery. Get a charge-combiner (there are many of them out there) that keeps the starting battery isolated from the house when not charging and, as the name implies, combines them when charging. You can use the switch to select the house bank as the primarily active bank, and then if for some reason your starting battery is too dead to start the engine, if you flip the switch to "both" it will connect the house with the starting bank and give you more starting current.
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Old 16-09-2014, 15:38   #10
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Re: Building a 3 Bank System, need help Bigtime

+1 for big house bank and one start (or backup) battery. No reason to have your house bank split.

On my (comparatively tiny) boat that's exactly what I did. A "big" house bank of 2 GC2's and a "reserve" battery of a single G24. I'll check the voltage and/or start off the G24 every now and then to make sure it still works. But for everything else, the switch is always at "1" - I start off the house bank. (But the A4 doesn't need much juice to start)

I'm so cheap I just charge the G24 with a diode isolator, but you should use a Echocharge or something.
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Old 16-09-2014, 17:56   #11
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Re: Building a 3 Bank System, need help Bigtime

Thanks a lot everyone! I'm still catching up, but this has really helped keep me from pursuing a silly unnecessary setup of 3 banks.

The reason I was looking into 3 banks was that i had 8 batteries total (2 are 12v for the starting bank) and I wanted to put 4 on each side of the boat for balance. The part that worried me was having 5 foot distance between the four 6v and the last 2 6v, resulting in the farther 6v batteries being undercharged if all 6v are in the same series parallel bank. Either way, I've been told I wont have too much to worry about if I get heavy gauge cable so there isnt much reason to run 2 separate house banks. I've also been told I could run the 4 battery and the 2 battery connections on top of eachother at the switch, basically linking the 2 banks like that making 1 bank...

So that solves that problem!

Now, the part that I still dont understand is how the charge controller/ACR fits into the wiring diagram. Will i have power from Solar and Wind generators coming into the charge controller, then the charge controller redirects the charge to whatever of the 2 banks needs it? The alternator, then, feeds into the 1,2,ALL,OFF switch and whenever the switch is on ALL it charges both banks, right? And shore power goes through the 110AC breaker, then the battery charger, then to the batteries, eh? So the batteries can be charged from 3 sources: the charge controller (solar and wind), the battery charger (shore power) and from the alternator which runs through the 1,2,ALL,OFF switch... is this all correct?

Also, can I have 2 12v batteries in parallel to start the engine? Is that wise or even helpful?

I'm going to draw something out and upload it and have ya'll tear it apart so I understand better.... anyway this is a HUGE help so thanks to everyone!
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Old 16-09-2014, 18:17   #12
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Re: Building a 3 Bank System, need help Bigtime

Connect the alternator and charger to the house bank directly as in right to the terminals. Then install a duo or echo charger which will "steal" power from the house bank and will charge the back up battery. Loose one of the 27s unless you have a really big or bad engine you wont need it.

Dont know about the controller I dont have solar and dont want to speculate.

Leave the switch on 1 and go sailing. Start the engine on 1 and motor to dock. Plug into shore power and leave it on 1. (Catching my drift?)

Only switch to 2 if you are at anchor and pass out drunk and somehow drain your house bank to nothing and it wont start the engine. (Ask me how i know) After you use your back up to start put the switch back to 1 and go motoring.

Rinse lather and repeat
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Old 16-09-2014, 18:32   #13
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Re: Building a 3 Bank System, need help Bigtime



Is this remotely what we're talking about here? I know its messy, but as soon as I can get a general idea of whats going on I'll be able to move forward quickly.

@ontherocks, I see what youre saying about having the second bank serve as a reserve for starting the engine with a charge controller running from the house bank to the reserve bank. would this require 2 controllers? One for the incoming power from Solar and Wind, and a second for the link between house and reserve banks?
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Old 16-09-2014, 18:52   #14
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Re: Building a 3 Bank System, need help Bigtime

I kinda have a similar situation as you and I will probably go to SINGLE bank in the future. You may want to read this:

Deep-Cycle Flooded/wet lead-acid batteries used as STARTER batteries? (Trojan T-105)
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Old 16-09-2014, 19:20   #15
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Re: Building a 3 Bank System, need help Bigtime

No more like this. Keep it simple. Everything goes to the main bank.
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