Ideal Battery Bank Wiring

[nigel1]

Originally Posted by sailcrazy

HogHead, I rebuilt the 12vDC system on our Taswell 43 back in 2002, and installed 6-Trogen T-105s (6v) watered batteries for power. I used a scheme very similar to Lars L's drawing. I set it up so I have 3-12v "batteries". Each 12v (+) is connected an On/Off switch. That sw then goes to a common bus, also with an On/Off sw, then to a house fuse, and on to the dist panel. The 12v (-) all go to a common bus. The system allows me to isolate any one "12v battery from the system, or to remove all 12v power with a single sw. My alternator output and my solar and windgen feed the common bus, but my 3-legged battery charger is connected to each "12v Battery" individually. Its been in use now for 13 years, works as I had hoped, allows me to isolate/remove a bad battery when I need to, and allows me to monitor each "12v battery" via the individual monitors. FWIW

Interesting about the battery charger. So the three outputs from the charger go to the three "12 Volt Batteries".
Are the "three" batteries common when you use the battery charger?

[sailcrazy]

Nigel1...Yes they are! Each of the 3 battery charger feeds goes directly to the (+) post of that respective "12v battery". I do not understand all I know about that, and I was concerned too-----but when I switch on the battery charger (a ProMariner 50-3) and monitor each battery on the batt. monitors, they are each being fed at different rates (amps charge). That tells me they are being individually charged, as ea "12v battery" needs. As I mentioned, its been working great since 2002!

[nigel1]

Thanks, good to know.

[Roy M]

Here's a picture of a 4X6 volt combo. Just add two more in parallel: These are L16 flooded batteries which yield about 700 Ah.

[skipmac]

Originally Posted by rwidman

While much has been made of having equal length cables, it's more important that the cables have a high enough capacity. This is a situation where a few more dollars spent on heavier cables will pay off.

Absolutely. If undersized then cable length will make a difference but with proper cables not enough to count.

Also there was quite a discussion on the benefit or even the necessity of running the + and - cables to opposite ends of the bank. The logic of course being both cables to one battery (or series pair of 2 X 6 V batteries) at the end of a parallel grouping the batteries at the other end would see lower voltage, less charge than the others and the batteries closest to the connections would be supplying more of the load, etc.

There was a very detailed response to that from CF member with supporting math that said in a normal house bank with small to moderate loads this would really not make any difference. This does assume that all connections are clean and tight.

Another thing that is often forgotten, the orientation of the batteries matters. If the batteries are installed with the plates running athwartship, when you are heeled over the liquid will run to lee side and the plates can be uncovered on the windward side. Batteries should be installed with the plates running fore and aft to eliminate this problem. Thanks to Sailorchic for reminding me of this issue (who I believe picked it up from Mainesail). One of those things I used to know but forgot.

[rwidman]

Originally Posted by skipmac

.......... Another thing that is often forgotten, the orientation of the batteries matters. If the batteries are installed with the plates running athwartship, when you are heeled over the liquid will run to lee side and the plates can be uncovered on the windward side. Batteries should be installed with the plates running fore and aft to eliminate this problem. Thanks to Sailorchic for reminding me of this issue (who I believe picked it up from Mainesail). One of those things I used to know but forgot.

On a sailboat and with flooded cell batteries.

[skipmac]

Originally Posted by rwidman

On a sailboat and with flooded cell batteries.

Forgot you are on the dark side of cruising but then I've been there before myself.

So take a power boat out in a beam sea and you can uncover the plates on either side of the battery as you roll.

[rwidman]

Originally Posted by skipmac

Forgot you are on the dark side of cruising but then I've been there before myself.

So take a power boat out in a beam sea and you can uncover the plates on either side of the battery as you roll.

I have AGMs.

[Chuck Hawley]

I also agree that have low resistance cables and terminations is perhaps more important than measuring every cm of cable length. What is very important is to fuse each bank of batteries at the positive terminal or near the positive terminal. I have three Group 27 AGM batteries for my house bank, and I used the Blue Sea Systems battery terminal fuses to protect them, should one battery get a shorted cell. I don't independently switch them, so I cannot easily take one "off line" if the need arises. Therefore, each positive terminal has a 100A fuse on it.

Chuck

[Wind River]

Originally Posted by Lars_L

The total length of cables to one pair of batteries should be the same for all.
I.E.
Pair 1.
The cable between the plus bar and battery plus pole 0.5 m.
The cable between the two batteries 0.2 m.
The cable between battery minus pole and the minus bar 0.3 m.
Total cable length 0.5 + 0.2 + 0.3 = 1.0 m.

Pair 2.
The cable between the plus bar and battery plus pole 0.4 m.
The cable between the two batteries 0.2 m.
The cable between battery minus pole and the minus bar 0.4 m.
Total cable length 0.4 + 0.2 + 0.4 = 1.0 m. (the same as pair 1)

Pair 3.
The cable between the plus bar and battery plus pole 0.3 m.
The cable between the two batteries 0.3 m.
The cable between battery minus pole and the minus bar 0.4 m.
Total cable length 0.3 + 0.3 + 0.4 = 1.0 m. (the same as pair 1 and 2)

If you from other calculations have come to that you should have 70 mm² cables, then the cables between the batteries and the bar would have been enough with 25 mm², but put 35 mm².

Each big consumer has its own fuse. I.e. the starter engine need a 150 A fuse, but it should have a fuse. The electrical distribution panel can have a 40 A fuse. Fuses of type MIDI would be enough for the most installations.

With this configuration you can disconnect on battery pair for i.e. maintenance charge, while you live on the other batteries.

If there should be a short circuit in one cell, the fuse to that battery pair will blow, and you will not notice it.

I am intrigued by this set up.
I am currently connected as per the picture in post #4

I like the benefits of this set up as stated here. Is there any disadvantage of this type of set up? Presuming no dis-similar resistance in cables and connections, will the batteries still stay balance in there charge and discharge cycles?
Can each negative wire coming from each battery set, be wired together so as to only have one connection at the bus bar or shunt with out any ill effects?

[SeaSon]

Hoghead, your diagram is fine. Do not connect your charge/load cables to the end, tap from the batteries in the middle. There are always voltage drops and this will help even out charge and discharge across the bank.

Regarding fuses, yes you should have one. It is a lot easier and a neater installation to have just one fuse assembly prior to your distribution bus, but it should be within a few feet of the bank. Also, it doesn't seem rational to have one bank's fuse burn out without determining the reason or to not notice it. You're not likely to ever be blowing a 150A or 200A fuse without a lot of mayhem going on.

[Lars_L]

That there should be the same length of cable to each battery is not so important when the loads are low. But today when the boots often have a big inverter, which has a large load (for use of microwave oven or vacuum cleaner), the cables shall have the same length. The cables need to be joined, and the best and nicest place to that is on the bar. There it is also easy to make the right length of the cables. A problem with this connection is where you should install the shunt for the battery monitor. One solution is to have a separate monitor for each battery pair. Another solution is to make two bares, one where the cables from the batteries are connected and another where all other ting are connected. Between those two bares are the shunt mounted.