Multiple battery banks or one big one

[Dulcesuenos]

We went with one bank of 6 x6 volt Trojans, our yanmar 2gm20s only pull about 80 amps for less than a second and our engines are running. Don't feel we need a separate start battery. Btw, our last 3 out of 4 cats were set up like this and never a problem.

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[ramblinrod]

Originally Posted by barnakiel

OK.

I understand 6V sells are smaller and lighter so when the bank is very big, some of us will elect 2 or 6 Volt cells over 12 volt ones.

"One bad apple kills the bank" is only a non supervised scenario. Every time I had a fail (2 times altogether, not much of a sample) I was able to tell there was a battery problem and I removed the bad one without suffering any damage to the whole bank (other than ending up with a smaller bank).

Cheers,
b.

I'm not sure this is true.

I personally think 6 volt batteries are not as superior as many believe.

Comparing apples to apples, w-hrs, weight, and volume, 6 volt batteries and 12 volt Grp 27 of similar quality are pretty much equal.

And 6 volt batteries have the disadvantage that it takes two to achieve 12 volts. If one develops a shorted cell, 2 have to be isolated from the bank. Not so with Gpr 27s in a 12 volt system.

[jkindredpdx]

I have two old fashioned banks with an AB switch... my boat is 42 years old and it still works.

[Terra Nova]

Originally Posted by ramblinrod

...If one develops a shorted cell, 2 have to be isolated from the bank...

No, you replace it.

[Dulcesuenos]

Originally Posted by ramblinrod

I'm not sure this is true.

I personally think 6 volt batteries are not as superior as many believe.

Comparing apples to apples, w-hrs, weight, and volume, 6 volt batteries and 12 volt Grp 27 of similar quality are pretty much equal.

And 6 volt batteries have the disadvantage that it takes two to achieve 12 volts. If one develops a shorted cell, 2 have to be isolated from the bank. Not so with Gpr 27s in a 12 volt system.

This explains why the 6v true deep cycle batteries are better. It really comes down To increased plate thickness and increased cycle life Huge difference imhop in a constant use liveaboard or cruising application.

http://www.power-talk.net/golf-cart-batteries.html



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[Thorne]

Originally Posted by Frankly

I have three sets of 6V GC batteries (Sam's Club for over 20 years). Two sets are fed to a common bus bar via a 1/2/both switch and the fwd pair is connected to the common bus bar through a switch. Fuses all around. The fwd bank is tapped to feed a bow thruster, windlass, and a couple of other light loads. No starting battery. All batteries are connected in normal operation, but the switches give me the option of testing each set individually (starting the Yanmar) and isolating a set if something goes south. On rare occasions when I have run the bank down, I have just switched out a set and that becomes the starting set until I can recharge them all.

I have been using this setup for over 10 years (not a live aboard but made several two month cruises). Worked out well for our style of cruising.

Ok, I'm in. I have switched my 2 banks to the "both" position. Great now I have both running and being charged full time ( when on shore power, solar only when not).

As to my separate windless and starter batteries.....

They are currently 12 volt. They are connected by a set of # 6 or 4 wire that is 35 ft. long making it possible to "Charge the windless battery" but not "Run" the windless.

So you have 4 6v batteries in the bow as well as 8 6v batteries in the engine compartment.

How do you charge the forward batteries?

Do you start your engine off the house bank?

If you run your house bank down, how do you start your engine?

Can you connect the forward batteries in an isolated way so you can start the engine. (avoiding the situation of only having 1/3rd the amperage you need it they were all connected together)

How big an engine do you have?

I appreciate any information you can provide as these are all issues I have faced and I'm always looking for a better way to handle it.

I like the idea of having all batteries on the boat be the same type.

[a64pilot]

All Golf carts that I have seen were either 36 V or 48 V, both number divisible by 12.
If there were a 12V battery that would provide more power, last longer or be more durable or more economical, then I would assume it wouldn't take long for the word to get out and golf clubs would I'm sure switch over pretty quick.
Now I don't golf, never have, but I suspect that the 6V battery is still the standard for a golf cart?
I believe their use is actually pretty close to a boats use, except they may cycle deeper? We had a Golf cart years ago for our Daughter to drive around the neighborhood, that was my experience with one.

[reed1v]

Originally Posted by barnakiel

One big bank and a separate starter battery.

And use 12 V not 6 V units (if your boat is 12 Volt wired) - bad battery? remove the bad apple from the bank and keep on going.

Must be some US 6 Volt taboo or something?

b.

Well if you are not sailing to remote areas, one is ok. However, two or three separate banks provides some insurance if one bank goes bad. We also used individual 2 volt cells to make up our banks. Kept two cells as spares. Great amps, if one cell goes bad, just replace it with another. Also lot easier to lug around one cell than a whole battery.

[sailcrazy]

We redid our system back in 2002, when one of our 12v "house"" batteries developed an internal dead short and almost started a fire. Our system now has 6-6volt batteries, wired into 3-12v "house batteries". Each of these 3 connect to an On/Off sw, then to a "System On/Off" sw...if I ever needed to quickly remove all 12v power. We normally run with all switches on (one big bank).....but if any one of the 6-volts go bad, I can easily switch it off and out of the house system-and remove it from the boat. We also have an isolated "Start" battery for eng and genset starting-with a parallel sw so the house could be combined with the start battery if ever needed. Has worked perfectly since installation back in 2002.

[noelex 77]

If the OP means two house banks with a seperate start bank, I think this is a very good system.

Two house banks and one start bank beats one house bank and one start bank. In many situations the two house banks are better coupled, but there are times when separation is helpful.

Two house banks does have a small cost, weight and complexity penalty, but it is only one extra battery switch a small amount of wire so these drawbacks are minimal.

Can anyone point out a disadvantage that I have missed?

[Thorne]

Originally Posted by noelex 77

If the OP means two house banks with a seperate start bank, I think this is a very good system.

Two house banks and one start bank beats one house bank and one start bank. In many situations the two house banks are better coupled, but there are times when separation is helpful.

Two house banks does have a small cost, weight and complexity penalty, but it is only one extra battery switch a small amount of wire so these drawbacks are minimal.

Can anyone point out a disadvantage that I have missed?

Actually I have been wrestling with this very thing.
1. 12 volt auto/marine batteries are setup to be able to produce huge starting amps for short periods of time. ( so you can start the engine ) When fully charged they can do this repeatedly with no ill effects. Asking a deep cycle golf cart battery to do this at all is Very Hard on them. ( You might get only a year of service from them )
2. If you have any other heavy draw application such as a windless you have the same problem.
3. Having a windless that is 10 meters away from the battery is not practical and trying to start an engine from a battery that is 10 meters away has the same problem. Unless you can afford 60 feet of zero gauge wire you are not going to have good success on a large windless or a large engine... Mine is a 65 horse Perkins.

Hence I use 12 volt deep discharge marine batteries connected together w 4 gauge wire, for starting and windless and 6 volt for house power.


I dunno, it seems to work and gives me options when I screw up.

[noelex 77]

Originally Posted by Thorne

Asking a deep cycle golf cart battery to do this at all is Very Hard on them. ( You might get only a year of service from them )

This is true for one small deep cycle battery, but not a reasonable sized deep cycle house battery bank. This will start a marine diesel engine without any problems.

[Terra Nova]

Originally Posted by Thorne

...I use 12 volt deep discharge marine batteries connected together w 4 gauge wire...

I really doubt that. Maybe 4/0.

[Dulcesuenos]

Originally Posted by Thorne

Actually I have been wrestling with this very thing.
1. 12 volt auto/marine batteries are setup to be able to produce huge starting amps for short periods of time. ( so you can start the engine ) When fully charged they can do this repeatedly with no ill effects. Asking a deep cycle golf cart battery to do this at all is Very Hard on them. ( You might get only a year of service from them )
2. If you have any other heavy draw application such as a windless you have the same problem.
3. Having a windless that is 10 meters away from the battery is not practical and trying to start an engine from a battery that is 10 meters away has the same problem. Unless you can afford 60 feet of zero gauge wire you are not going to have good success on a large windless or a large engine... Mine is a 65 horse Perkins.

Hence I use 12 volt deep discharge marine batteries connected together w 4 gauge wire, for starting and windless and 6 volt for house power.


I dunno, it seems to work and gives me options when I screw up.

1.cranking for long periods of time is incredibly bad for a starter, might need.
2.. Most high torque starters draw alot less than their rating and only for a second or so if the engine is running properly.
3. Most people I know don't run the windlass for the initial drop or when weighing anchor without the engine running. Kind of negates worrying about a high battery draw.


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[Thorne]

Originally Posted by Terra Nova

I really doubt that. Maybe 4/0.

Thanks for the note: I meant wire size of 4 AWG.

https://en.wikipedia.org/wiki/American_wire_gauge

For easy reference.