Adding More Batteries

[BambooSailor]

I suggest that you get and read Nigel Calder's Boatowner's mechanical and electrical manual. He explains all the issues with batteries and battery banks in details. In summary, if you are willing to live with ineficiencies in your system and premature battery sulfation, your design MAY work. Otherwise follow his advice.

[osirissail]

- -Okay, If he wants an all electric boat that is his choice. I have a 1000 AH house bank and still have to charge daily as I have really a lot of electrical items that consume about 200 AH daily.
- - As to cable size for 12VDC over 20 feet (x2 = 40 feet) you need several considerations. First your main DC load circuit breaker is normally in the 40 to 50 amp range for a house bank. Not your battery switch, your house bank main c/b. If you do not have one you should install one. It limits the total draw on all sub-circuits to 50(or whatever) amps max. You use this amp size to enter the reference books and with length of wire (40feet) you get 2/0 copper wire for 50 amp and 1/0 for 40 amp.
- - At the remote batteries you need to install a bus fuse or high power c/b sized to the maximum current capability of the chosen cable size. I would use a 50 or 100 amp bus fuse or c/b so that "short term" shock loads could be tolerated before compromising the cables.
- - And - then if you run a smaller charging wire to the remote batteries - say 8 guage - then that wire needs its own 15 amp c/b at the source of charging end (main power panel or alternator branch off end) to protect overcurrent in the charging wire. This is especially important in remote batteries for windlass, bow thrusters, etc. which do not have main cables running back to the main battery bank.
- - All this is to prevent fires in your wireways which are normally behind lots of flammable stuff.
- - Separating AGM batteries physically by large distances is not conducive to long life as the control of charging voltages becomes difficult due to line loses. AGM's should be clustered as close together as physically possible and very tight voltage regulation is needed to prevent significant loss of battery life. With classical lead-acid batteries like the Trojan T-104's, etc. these charging considerations are not a critical factor.

[Bash]

Originally Posted by btrayfors

By my calculation, that makes 12 batteries @ 210AH each for a total of 2,520AH. As each one weighs in at 135lbs, that's 1,620lbs of batteries and @ about $500 each that's $6,000 worth of batteries.

Something very wrong is going on with a boat that needs a 2,500AH house bank.

Is it safe to assume that the other guys in your marina are complaining about it being so hot that their zincs don't last more than a couple months?

Time to consult a professional.

[bobfnbw]

Originally Posted by Randyonr3

I'm adding to my house bank.. At the present, I have 10 of the Lifeline
4d's aboard and am adding 2 more..
The 2 I'm adding will be mounted in what was the forward head area and now houses the watermaker and closet..
My question is,
what size cable do I need to run to the main part of the house bank as its about 20 feet from the intended placement of the new set?
At the present, I have 4 of the 4d's under the nav station, 2 4d's under the windless up front conected with 4ga. wire in paralel. another 2 of the 4d's under the galley area, and 2 more just forward of that in the main soloon, all with 6 ga. wire..
I was recently told that due to the large bank already in existance, All I really needed to run was 10 ga. with a 10 amp fuse in line to protect the line if for some reason, the house bank went poof.
The whole Idea was to create small banks of batteries at the "need for the Power"... and connect the smaller banks as one large bank..

Its a concept I thought about as well, but rejected. And here is why.
A battery has a finite life span. Say a lifeline agm battery will last you 5-6 years. Then you have to replace them. Thats a lot of money.

Instead maybe only have a smaller bank, and 4/0 wire to your loads like windlass, inverter, bilge pumps, and bow thruster.
Now when powering say the thruster or the windlass, you have your genset or your engine running and you get minimal voltage drop across the grid.
Your batteries will last a bit longer, and there will be less of them to replace.
The expense of the larger wire is moot, as it will last a long time, and not be replaced.
For that size boat, 800 amp hours should be more than sufficent I should think, with a good charging system to keep them up.
So if you run them between 40% and 80%, that is around 320 amp hours you have to deal with, and with some solar or wind gen thrown in, should last several days between charging.

Batteries are heavy, cost a lot, and have finite life spans. Seems better to go with a smaller bank and larger wire.
Thats what I am planning. 600 amp hours of tppl agms and possibly going to 800.

Also wouldn't it cost more in the long run for your idea with charging costs?
If you are using your main engine to charge, and your spread out like that, it will take longer to charge those batteries. Some will get charged faster than others, some will take longer..... costing you more money.
One bank, large wire, high charging rates.

[osirissail]

- - All batteries have a "life span" based on - charge/discharge cycles - not time. Depth of discharge will determine how many "cycles" you will get out of a battery. My last set of AGM's lasted 11 years but I never let them get more than 25% discharged before recharging. Discharge them to 50% and you will cut the number cycles available in half. That loosely translates to instead of 10-11 years you get only 5 years before replacements are needed. This is where have a "large" bank of batteries pays off.
- - Taking AGM/Gel Battery life down to 5 years or less drives the cost-effectiveness of using AGM/Gel batteries down through the floor. Generally speaking "exotic" batteries like AGM or Gel can cost up to 4 times the cost of a "lead-acid" battery such as the Trojan T-105's or even "truck" batteries (4D's and 8D's). "Truck" batteries are "deep cycle" batteries. They last from 2 to 4 years depending upon servicing and charging regimens. Comparing traditional liquid lead acid batteries with "smart charging" to the "exotics" (AGM/GEL) you get twice the life from the exotics for 4 times the price. Not very cost-effective - except - in one situation.
- - That is when you are planning to sail to places where batteries are not easily available. "Long-life" batteries make sense if you are going to sail around Cape Horn or wander the un-inhabited corners of the world. But anywhere else where trucks and vehicles are used daily you will find replacement liquid lead acid batteries available. And in little countries the Trojan T-105's are very cheap - better than USA prices because the local's use tens of thousands of them to run their household inverter systems.
- - If your boat does not have or cannot be modified to hold the T-105's then you are stuck with the battery format that will fit. But otherwise in normal "round-the-world" sailing, and especially coastal or island sailing replacement "normal" batteries is not a problem.

[Tidetracker]

Originally Posted by Randyonr3

The whole Idea was to create small banks of batteries at the "need for the Power"... and connect the smaller banks as one large bank..

As an electrical engineer with nearly 40 years of experience, I believe I can say with some expertise that paralleling batteries to increase total capacity is NOT a good idea, for both technical, as well as strategic, reasons.

Yes, I know... it's commonly done, especially in boats. That doesn't make it a good idea, though.

First, the technical reason: When batteries are brand new, their electrochemistries are equal, and paralleling two or more results in roughly the same draw of current (while discharging), and the same charging current (while charging) in each of the batteries.

Over time, however, the batteries do age... and they don't necessarily age equivalently. Nearing end of life, it's possible for one battery to develop problems in one or more cells, including a complete short. When that happens, the 'good' batteries begin to dump current into the 'bad battery, and they no longer share currents equally.

Although it doesn't happen that often, it's possible for multiple batteries in parallel to suffer catastrophic failure, including explosion, fire, or even just massive outgassing.... and the gases can make a genuine mess of the interior of any boat. I've seen this happen on at least one occasion.

Sure, there are applications, like submarines, where it would be impossible to create a single battery with enough capacity for the load... so the batteries are put into parallel... but with the ability to isolate each battery for separate testing or removal from service. But in the case of crusing sailboats, at least, I don't see why it's necessary. We lived off a pair of 4D wet cells, used one at a time, for years.... a single 4D was more than adequate to support refrigeration, electronics, and illumination for 24-36 hours, after which we would switch to the second battery. Usually, in a 72 hour period, we'd be recharging at least once, by running the engine. Obviously, if a boatowner insists on using a massive inverter to power things like microwave ovens, the situation will be different.

As for the strategic reason to not run batteries in parallel: it's an issue of recharge time. If your boat has unlimited alternator capacity (NEVER the case, in any sailboat I've ever seen), then it doesn't matter. But in a more practical application, your alternator does have limits.... and those limits may be a lot lower than you think. My own boat, a Jeanneau 43DS, has a '72 amp' alternator.... but what that means is that it is capable of putting out 72 amps briefly, at maximum RPM, for a few minutes while the windings are still relatively cool... after which, the output capability drops off. Under more practical charging conditions, the output is much lower.

With two batteries in parallel, and assuming they are new or in new condition, the current will split between the two, while charging... so each battery gets half the available charging current. If you charged them one at a time, ideal theory says it will take exactly the same total time to recharge them, as charging them in parallel.

However, in the real world, alternators and batteries are NOT linear devices... and if you demand twice the current from your alternator during recharge, you will get less than twice the current... because the alternator will heat up that much more, the winding resistances will rise with temperature, etc. It will actually be quicker to recharge the batteries one at a time, because the alternator will be more efficient with a lighter load.

So, how would you manage a battery system consisting of two batteries, used sequentially? It's actually quite easy.

Assume that both batteries are fully charged, you've been sailing all day, and you've used the engine enough to insure that both batteries are indeed fully charged. In the evening, you're on a hook or mooring... and you're using battery #1. In the morning, you start your engine on battery #1, and leave it there for enough time to top up that battery.... and when you stop for the evening, you switch to battery #2. The following morning, you let battery #2 recharge, and then that night, you switch back to battery #1.... and so on.

The result: you evenly wear your batteries, and you always have one fully charged battery available, should you deplete the other one before having had a chance to recharge it. It's a very simple strategy.... and easy to do.

As for what kind of batteries: I still don't think that AGM's are worth the money, despite the supposed advantages, like faster recharge time and position independence. Conventional wet cell batteries are incredibly cheap, and decent ones, cared for properly, are easily good for 5-6 seasons before needing replacement. The best deal, in $/amp-hour, are golf cart batteries.... two in series might cost $130, and provide around 225 aH of capacity, versus 180 aH for a 4D battery costing more than that.

[osirissail]

Tidetracker is right on with the technical theory of batteries and how to deal with them - but (there's always somebody's but around) - real life causes us to deal with compromises. Just like there isn't only one kind of sailboat - there are hundreds or more - batteries fall in the same situation. Production boats have specifically sized battery storage locations designed by the boat builders idea of what batteries should be used. They are generally very limited in size.
- - From 30+ years ago a battery was on board to only start the engine, we have seen boats progress into miniature "cruise liners" in the amounts of electric and electronic equipment on board. 10 years ago 50 to 75 amp hours per day was average usage. Now it is up to 150 to 200 amp hours per day as we add lights, inverters, ice makers, refrig/freezer operating on 12VDC, bow thruster, stern thrusters, microwaves, electric stoves, ad nauseum.
- - I think to operate most efficiently with one battery we would need a lead hull and fill the bilges with sulfuric acid - the whole boat would be the battery. Actually very silly - but the idea is that now we are faced with the need to compromise and start adding different sized batteries here, there, and everywhere possible in the boat. The original question was how to connect all these differently located batteries together.
- - The most important points mentioned was the need to "match" the age of all the "paralleled" batteries. And the need to have "disconnect" points between batteries to search for the early "dead" cell or a problem battery that is dragging down the others.
- - It is a very good idea to attach each paralleled group of batteries in one location to individual battery switch and to be able to bring that bank on-line or to easily isolate or locate a fault in that group. In real life that is too much work so everything is connected up into one giant bank. I use buss fuses to protect between banks and between the main feed to the main battery switch. A dead short in one bank or in some engine equipment, inverter, etc. can easily draw hundreds or a thousand amps down wire with nowhere near that capacity resulting in an electrical fire. I have seen this happen in several boats I have been called to repair. Having your boat burn to the waterline while out in the ocean is not a happy situation.

[Randyonr3]

Lot of great info guys.. and the reasoning behind the large amount of AGM was to provide the power we run on..
First off, the units I have on board have never been discharged to the 50% level..
and I dont think they have ever gone as low as 75%.. always opperating in the upper areas of 85% or better..
We've been OFF-THE-GRID for almost 7 years now and the system is still running smooth.. and we dont scrimp for anything.. My 110 system is run off a Zantrax inverter off the batteries.. power comes from two 80 watt solar panels, a 4-winds generator, and at times a genset .. and again, we're totally off the grid..
The only time I've seen the power drop was when we were running the watermaker for any length of time, over a period of hours
So the way I figure it, i may have over 2000 amp hours of storage but to keep the batteries above the 75% level, I have a usable amount of batteries in the 400 to 500 amp hours of storage.. On My boat its easy to see 200 amp hours used daily..
and every 3 or 4 days we turn the watermaker on for 10 or so hours.. 150 gal a day or roughly 6 gals per hour at 7 amps per hour is an easy 70 amp hours used. and I know that sounds like alot but you figure a couple gallons to flush the watermaker, showers for the wife and I each day.. 4 days thats 8 showers, washing the dishes and cloths if were away from the marina and guess what.. 50 to 60 gallons every 4 days... not to mention the Electra San and what it sucks every time you flush, in both electrics and water..
For us, cruising is not a lifestyle we scrimp to injoy..
As for the weight of the batteries, well the FIRST 42 was designed for a large crew while racing.. all I've done was swap the weight of the crew for the weight of the batteries....
and guys, this is NOT a new system, as I've been opperating and all is working fine for 7 years now.. I'm just adding to it..
and as far as the cost.. I figure 15 years at around $300.00 a year for a worry free system.. Not a bad expence in my book..

[Tidetracker]

Originally Posted by osirissail

- - I think to operate most efficiently with one battery we would need a lead hull and fill the bilges with sulfuric acid - the whole boat would be the battery. Actually very silly - but the idea is that now we are faced with the need to compromise and start adding different sized batteries here, there, and everywhere possible in the boat. The original question was how to connect all these differently located batteries together...

I think it depends entirely on just how one is using the electrical system. For the typical coastal-cruising sailboat, which represents the majority of boats in my marina, for example, a single 4D is more than enough for 36 hours worth of refrigeration, lights, nav instruments, radio/TV, etc... so a pair of them, used sequentially, is a very practical arrangement.

Obviously, this won't suit everyone. A freind of mine with a 41' Hunter keeps his boat on a mooring, and wants to be able to keep his refrigeration up and running during the workweek... he also wants to be able to use his microwave oven while out on the hook (via a huge inverter)... so he installed a fairly large solar panel, and a wind generator.... and those feed a bank of 8 golf cart batteries (about 900 amp-hours total). In his case, the risk of paralleling batteries is judged to be a lower priority than the need to keep his food fresh, week to week, and use the microwave.

Different cruising styles obviously have differing requirements.

[MarkJ]

Originally Posted by Randyonr3

For us, cruising is not a lifestyle we scrimp to injoy..

I'm sure youv'e got a Spa Bath (Turbo with bubble maker)

[Jon D]

Randy

I understand the need for big banks - what I'm amazed at his you have over double what I have 840 Ahrs house bank and 220 Ahrs start bank and we also subscribe to the we are living not scrimping class of cruisers. I just can't imagine where you have the room. We filled out boat with spares etc and finding room for more batteries without impacting our storage for "stuff' which includes food. Now admittedly we do run our bank lower than 75% but almost never down to 50%.

[bobfnbw]

Yeah, I would go with more food, more spares, than that amount of batteries.
But to each his own.
Seems like you could get the same effect with less batteries and just replace them a bit more frequently.
Now if your down around patagoinia, I could understand.

[osirissail]

And actually after you get out there for months and years anchoring out you do find that having enormous battery banks is not such a great idea. I see most often the size capping at about 800 to 1000 Ah. There is just too much servicing required for larger banks and the cost of replacements is "Retail Plus freight" down here. One 8D AGM goes for close to US$1,000. A 4D is not that much less. So what is happening as the load demands increase? Honda EU2000i's are the "hot item". Quiet, run forever on a little gasoline and put out 13 amps of 120VAC. Rather than run your main diesel engine at low power and burning more diesel you start the Honda and supply your microwave or a small window airconditioner and charge your batteries. It is almost standard to see these little gems hooded and tied to the mast or aft rail.

[Randyonr3]

The origional question was concerning the size of wire to be used and one person, David seemed to answer the question.. but it seems that the rest of you want to re-design a system on my boat that works and works well..
Batteries are a strange subject and many different items need to be taken into account when designing and opperating a system.. I agree that to use less of a bank and to replace more often is One design, but I have chosen a different design. and using an AGM Gel is as different from lead/acid as apples and oranges.. Yes, they're still storage devices but they opperate differently in charging and discharging and in safety issues.. Gell cells are good for an accounted amount of discharges and charges and if you can alter the discharges and work the batteries in the upper end of the system, then you will have a system that not only is dependable but worry free.. and I'm speeking from experance as the system is working fine..
Its just like opperating the batteries in a golf cart.. where a cart is rented out and used every day to its extreme, and the batteries are run to death and often by the end of a season need replacement but on the other hand, the same batteries in a personal cart, where a guy uses it for 3 or 4 hours, takes it home and puts it on a quality charger, the batteries are known to last for many years..
Its all in the way you treat your system..
And when I say scrimp, Its not that we run a hot-tub on the boat.. but the usage, if only for a brief moment, is used to extreme, I'm covered..
So lets take one instance, this morning, I went to the head, flushed it, the electro-san kicked on.... while still standing there, I turn on the water for a shower, (electro-san & 1-pump).. next the shower sump kicks on (electro-san & 2 pumps)... the wife in the galley starts filling the coffee pot for coffee.. (electro-san & 3 pumps)... the shower pump starts to make noise as it running out of water, so I yell and the wife hits the transfer from the right tank to the left (electro-san & 4 pumps) and at the asme time she she hits the transfer pump, she turns the watermaker on to fill the first tank..(electro-san & 4 pumps & a watermaker).. the coffee pot is full so one pump shuts off but the coffee pot is turned on sucking juce fromthe inverter..
so for a brief moment, all frommy battery bank, I have an electro-san, 3 pumps, a watermaker, and the inverter making coffee...all sucking from the system...
and oh yes, the TV is on watching the charmed ones, and it been kinda mucky out so 2 fans are running in the main cabin..and somewhere in there the wife has had the toster on.. and could be the refer was on......
All of this is off the battery bank...........
Now in a few minutes all will drop back to maybe a 10amp draw as only the watermaker, fans and TV are on...
But for a short amount of time, I need power,
We do use the genset from time to time as its needed to run the waterheater and finedit best used in the morning when the need is at its max but even with the gen-set, we need the batteries to take up the slack.....

[GordMay]

Originally Posted by Randyonr3

The origional question was concerning the size of wire to be used and one person, David seemed to answer the question.. but it seems that the rest of you want to re-design a system on my boat that works and works well...

Generally, more information is better - but sometimes it becomes a confusion of choices.

The industry standard formula for calculating minimum Wire Size for a given Voltage Drop is:

CM = (K x A x L) ÷ VD
Where:
CM = The Circular Mil cross sectional area of the wire
(See Table 1, and ABYC Section E-8, Table III)
K = 10.75 Representing the Mil-Foot Resistance of Copper Wire @ 78o F.
L = The Total Length of the wire in Feet
(This is the ‘Round Trip’ length of both Positive + Negative wires)
VD = Permitted Drop in Volts
(Ie: 3% @ 12.5V = 0.375 ED or 3% @ 25V = 0.750 ED)

This formula does not address the resistance added to a circuit by it’s terminations (joints & splices). The reality is that each “old’ termination could, after a time in service, add a resistance of between 0.01 and 0.03 Ohms to the circuit. This additional resistance is, in many installations, greater than that of the wire!

For those that don’t wish to perform their own calculations, I’ve prepared a chart where all you have to do is multiply the Circuit Amperage times the Total Wire Length (Positive + Negative), resulting in Amp-Feet. The chart displays the Amp-Feet rating for various wire sizes, based upon a maximum Voltage Drop of 3%.

Goto ➥ http://www.cruisersforum.com/gallery...r&imageuser=79

And ➥ http://www.cruisersforum.com/gallery...r&imageuser=79