Wiring In Series (pro vs con)

[ramblinrod]

Originally Posted by TeddyDiver

Despite Rod hates the frase, "true" deep cycle batteries have more reserve space below the plates to avoid such issues. That's on reason why they are higher..

BR Teddy

But the problem with "higher" batteries is that they do no dissipate heat as well.

(This is why I disagree with water baths during testing, as it alters the natural ability to dissipate heat via natural convection, and favours taller batteries).

Additionally, while golf cart batteries tend to have more space below the cells, (to collect the greater amount of shedded material from the thicker plates needed to carry the higher current in a package that doesn't dissipate heat as well) they tend to have less reservoir above the plates, which makes them more sensitive to lengthwise orientation, and more likely to suffer from plate exposure and all of the problems that entails.

And then of course, there is the issue that they may not fit in original battery boxes and require vessel modification to accommodate. Anything is doable, the question is, "Is it really worth it?" In my opinion, changing from 12 Vdc batteries to Golf Car batteries or 2 Vdc cells, or something even less commonly available everywhere, is rarely worth it, except to the vendor peddling alternative, more expensive, solutions.

[rwidman]

Originally Posted by TeddyDiver

Nope, a cell in this regard consists of the vessel the plates and the electrolyte. A battery has also positive and negative external contacts..

BR Teddy

Huh?

[ramblinrod]

RR: Well, if you don't post what you mean, all we can do is guess.

TD: We? I think it's just you.

RR: Could be just me, the Royal we. ;-) But quite frankly, the responses are twisting in the wind every which way from Sunday. "I didn't post that", but later, "Yes I really did mean that." It's just nonsense gibberish. Especially after declaring in a post long ago in the thread, "I'm not going to argue".

RR: A previous poster indicated a bank consisting of 2Vdc cells in series is the ultimate. Based on the content of your post, I thought you were agreeing with that statement.

If this is not the case, why don't share with us what you do mean?

TD: The previous poster is right. I do agree with him.

RR: You have every right to agree with a poster that a house bank consisting solely of a series string of batteries is a proper solution, but in my opinion, that does not make it right. In fact, I believe that is very bad design not to include simple redundancy to compensate for likely battery failure.

RR: How so? If one is designing a 12 Vdc system, how does using 12 Vdc batteries limit options, other than not using batteries of different voltage. There are certainly sufficient options of 12 Vdc batteries available to meet any reasonable cruisers budget and life expectancy needs.

TD: Not real deep cycle batteries, and not in sizes (for obvious reasons) big enough to avoid unnesessary paralled batteries when more capacity is needed.

RR: Excuse me? If one wants to avoid paralleling batteries, 12 V batteries are available in pretty much every size imaginable from many different manufacturers. Personally, I think that would be stupid, because of the weight, cost, and lack of redundancy when that battery fails. But certainly, very reliable 12 Volt DC batteries of pretty much any form factor are available if one is will to pay a premium for higher quality.

Secondly, I do not believe there is any valid reason to avoid "paralleling batteries". Just because a battery can be made of a series string, doesn't mean it should be done that way, for all of the reasons previously stated.

RR: I disagree. A programmable loading device can help to monitor battery capacity. (An analog 12 Vdc load tester will do pretty much the same thing for 12 Vdc FLA batteries, albeit with a 100 A fixed load, for way, way, way less money.) Neither of these devices will do anything to address the lack of redundancy in a 12 Vdc house bank consisting of a 2 Vdc series string.

TD: I'll comment to this topic later

RR: Looking forward to it.

RB: How so?

a) If a 2 Vdc cell fails, in a 6 x 2 Vdc bank, it will reduce the voltage available by 2.15 Vdc (at full charge). For all intents and purposes, the bank is dead,
until that cell is replaced.

TD:No it's not dead. It's a 10Vdc bank. It can feed any electronic devices in a boat with DC to DC converter https://www.digikey.com/product-deta...263-ND/4477521
Most quality inverters also accept lower than the nominal 12v voltage.

RR: By definition, a 12 Vdc (nominal) battery, with a state of charge less than 10.5 Vdc, is considered "dead" (or more accurately, "exhausted" or "fully discharged" and in need of immediate re-charge).

If a defective 2 Vdc cell is removed from a series string of 6 (as required to make 12 Vdc nominal), the remaining voltage will be below the drop-out voltage of many devices. When loads are applied, and voltage sags, even more devices will drop out. As the remaining batteries are discharged, the voltage will fall even further, to the point where no (or very few) 12 Vdc devices will continue to operate. The boat is now dead in the water. The normal charging systems cannot be activated, or the charge voltage will be too high for the remaining batteries. One solution may be to reprogram all or some of the charging source voltages (shore power, solar, alternator regulator, wind, water, etc.) Fun times as sea, in the middle of a storm, when the violent motion may cause a shorted cell.

Your digikey link didn't work for me, but no matter, I know what a DC-DC converter is, and how costly they are for anything that produces the kind of current that may be necessary to run all 12 Vdc loads off a 10 Vdc bank.

Sorry, while I certainly understand this is possible, I don't feel it is a "reasonable" solution. A much better, lower cost solution, is to simply have 12 Vdc cells in parallel, so that when one gives up the ghost at the most inopportune time, one just flips a switch to isolate that battery from the bank, and carries on.

How much more equipment are we going to buy and install, to compensate for the fact that a house bank consisting solely of a series string of batteries has no natural redundancy? Again, just because we can do something, doesn't mean we should. Just about anything can be done, regardless how ridiculous the complexity and cost.

RR: b) If a cell in a 12 Vdc house bank battery fails, it will reduce the voltage available by 2.15 Vdc, until the defective battery is disconnected (by simply flipping the isolation switch or disconnecting the terminal).

TD: That is if you happen to detect the failure in time and what kind of failure is in question. Worst case scenario, and not unknown, is short circuited cell which can destroy your paralled bank and even your boat totally. Best case uneven loading and charging shortens the life of other batteries in the bank untill the failure is detected. How often an avarage sailor is equalizing and capacity testing their batteries individually?

RR: Red Herring - Any 12 Vdc bank I have encountered with a battery having a shorted cell, exhibited the following symptoms:

1. The defective battery pulled down the bank voltage to 10 Vdc.
2. Things immediately start working very poorly if at all, which is very obvious to even the most non-electrically inclined boater.
3. When charging was applied, the defective battery gassed off, another indicator to even the most in-informed boater, that something is seriously wrong.
4. The defective battery was isolated from the bank.
5. The normal charging systems bring the bank back up to 12 Vdc nominal.
6. The boater continues on, replacing the defective battery at the earliest convenience, (which may be months in some remote locations), or they may elect to not bother replacing the battery at all, and just continue to operate with reduced energy storage capacity, but with all systems working fine, and no charging system alteration required.

RR:After which, all other batteries in the bank should now function properly.

Or not..

In my experience, if the remainder of the bank was "good" to begin with, and a shorted cell in one is experienced and corrected (as it has to be to make things work, as 10 Vdc is insufficient to run most things), the remaining batteries are not "hurt" at all, (other than the life expectancy reduction from one deep discharge, which in the grand scheme is virtually negligible).

The shore power charger will still work, the alternator will still work, the solar charge controller will still work, and the wind or water powered generator will still work. Nothing else to do, but charge up the depleted bank by normal means. At one's leisure, they can replace the defective battery, to restore full capacity.

If the shorted cell occurs when nobody is on the boat, and the bank is held at 10 Vdc for a long time, it is possible that the life expectancy of the remainder of the bank will suffer greater loss.

BUT, generally, a shorted cell occurs when a battery is near, at, or beyond its normal life expectancy, so quite frankly the entire bank needed replacing anyway.

TD: And 6 x 2Vdc user can put a spare 2Vdc battery in place of the faulty one

RR: Gimme a break. Now the boater is to carry around a spare 2 Vdc cell, to address that fact that he is so screwed if a cell shorts. What a belt an suspenders solution, install an expensive DC-DC converter, and carry around a bunch of dead weight, to address the eventuality of a shorted cell, rather than just have a 12 VDC bank that is fully functional all of the time?

I'm sorry, this is becoming more preposterous with every post.

RR: So please, enlighten me with how a series string of 2 Vdc cells, has adequate redundancy in a 12 Vdc nominal system to compensate for a shorted cell?

TD: You tell me have you ever heard 2Vdc deep cycle battery shorted.

RR: No. Not because it doesn't happen, but because of all my customers, I do not have a single one, that has a 6 x 2Vdc series string house bank, and if one ever suggested, I would do everything I possibly to dissuade them, as a courtesy service. If they insisted, I would warn the consequences, take their money, and install it, because after all, it is their boat. I would certainly never install this type of system on my boat.

RR: Poor (open) Connection:

Series String: All current stops. Dead. Nothing works until repair made, despite how many good connections there are in the string. Fix now to get anything to work.

TD: Instantly notes the fault. Disconnect or replace the faulty battery. See above.

RR: OK, so we are in the middle of a storm, 500 miles from nowhere. The 2vdc cell shorts. Systems start failing all over the place, so the boater instantly notes the fault. Now they go down and reprogram their DC-DC converter (that they only need because of their silly house bank configuration), nad reprogram all of their charging systems (if possible) so that they can recharge the bank as it depletes, or remove and install a spare, heavy, 2Vdc cell that they have carrying around in a partial state of charge condition due to self-discharge, possibly in tropical climate, that has been adequately secured somewhere, so it is not a loose cannon, probably taking up prime storage space. And if they don't have a DC-DC converter, or a spare 2 Vdc cell, or sufficient charging system programmability, sit their with all 12 Vdc devices lost, until they can get somewhere, days, weeks, or months, and then sit in a marina for more days, weeks, months, waiting for delivery of another 2Vdc cell.

All this, instead of just using 12 Vdc batteries and just flicking a cheap isolation switch, or disconnecting a terminal, and continuing on as normal until they reach a port where 12Vdc batteries are immediately available at low cost?

RR: Parallel Bank: 12 Vdc still available. Everything still works (except the battery(s) disconnected by the open circuit). Fix at your leisure to restore full capacity.

TD: If and when you come aware of the fault, that is if you don't wake up to the smell of battery acid or worse.

Now wait just a minute, why would the boater with a 2Vdc cell string be instantly aware, and the boater with a 12Vdc house bank, maybe never becoming aware. Totally illogical.

If a shorted cell occurs in either configuration, the boater will smell hydrogen sulphide, a pungent odor that will help to indicate there is something seriously wrong with the house bank.

And that tall, skinny, shorted 2Vdc cell is gonna get hotter than a witch's +!+.

RR: Internal Resistance Differs:

Series String: Charge current and capacity through all cells is reduced until defective cell replaced.

TD: Again, instant knowledge of the issue due longer charging times.

RR: With any configuration, if battery impedance changes, and batteries are monitored, it will be apparent.

Parallel Bank: Lower impedance batteries accept greater charge current, (as ususal).

TD: And after charging them up they start to charge the high impedance battery. Reduces battery life..

RR: With a 12 Vdc parallel bank, one can easily perform an equalization regularly. Much more difficult to do with 2Vdc cells.

Water Level:

RR: If someone neglects to add water to a vented battery, catastrophic battery failure will eventually occur.

TD: Hydro caps recommended.

RR: Oh sure, just through more money at it. After all, that seems to be your recommended solution for everything.

RR: Series String: The entire string is disabled, and everything is dead, until the defective cell is replaced.

TD: See above

RR: See above.

RB: Parallel Bank: Disconnect the defective battery, the rest of the bank works fine, operating all 12 Vdc devices until the battery is replaced to restore full capacity.

Originally Posted by TeddyDiver

I don't expect you to change your mind.

BR Teddy

RR: Ahah! You got that right! I am not about to change my position on this subject, based on weak arguments and flawed logic.

I really don't care what any individual does on their boat.

But when someone starts suggesting, promoting, advising, or recommending flawed solutions to others, in an attempt to justify their actions and expenditures in their own mind, I feel compelled to illustrate the flaws in the proposal, so that others aren't lured into overly expensive, complicated, inconvenient, and potentially dangerous situations.

[ka4wja]

Rick, et al,
You're very welcome!!
Please be sure to read my last comment, at the bottom of this post!! (it's really important!!)

Originally Posted by rwells36

John,

What a breath of fresh air! Going with 8 12v AGM Fire Fly in series / parallel and have hired engineers for drawings and installation.

Thanks for all the input and posts from everyone.

Cheers!

Rick

FYI....there are a couple additional clarifications / comments.....

1) I assume these are 6-volt batteries??
For a 12 volt system, to have batteries in a series / parallel configuration, they'd not be 12-volt batteries....
And, why "8" batteries, to get 900A/H??
I assume these are 6-volt, 225 A/H, batteries....where four series pairs, are placed in parallel??


2) As for AGM's....
While in theory, when comparing similar battery sizes / spec's, and similar battery costs....AGM's are darn close to "wet-type" batteries in their performance / life-cycles....BUT...
But, in the real world, almost all cruisers who have used AGM batteries (whether Lifeline, Concord, Firefly, etc.) have found an almost necessity of getting them back to 100% SOC on a fairly regular basis, in order to get close-to their rated "life-cycles" / life-spans....

The fact is that if you have lots of solar (or plug-in to shore power every night) and can make sure that you can get your batteries back to 100% charge regularly (daily??), then AGM's can be a good choice for some....
But, even with the high charge acceptance rate of AGM's (in bulk charging), getting that last 10% of charge (from 90% to 100%), takes time!!
And, if you cannot be sure that you'll get them back to 100% regularly, most will not recommend AGM's....


3) As for what is "deep cycle"?? Well, I don't want to get into an argument, but there are real engineering criteria to use here...
I mean, there are some that talk about "true deep cycle", and there's no problem with this....but, a definition might be helpful...yes??
SO...

So, for those that wish to have a better understanding of what this term "deep cycle" refers to...
Most sailors (end users) consider this in reference to how many deep discharge (to 50% SOC or below) cycles a battery will survive and still have near to its rated capacity (~ 95% or more) when fully charged...
This is usually referred to as the number of "life-cycles"...

And, while there are engineering and scientific specifications that actually determine this...such as the thickness of the positive plate, as well as the plate chemistry....most end users (and embarrassingly, many battery retailers and distributors, too) are unaware of these criteria, so they are simply "sold" on the "number of lab cycles" (usually known as the battery's "life cycle")...therefore in our sailing world, "deep-cycle" and "true deep cycle" have become rather "subjective" terms...

Most will say that any battery that has a spec'd lab "life-cycle" down to 50% SOC of > 1000 cycles is "true deep cycle"....some might say this is reached by batteries spec'd at 750-800 life-cycles....and I personally place the definition at 1250 and over (but, I use the engineering and chemistry to really determine this)

FYI, positive plate thickness needs to be 0.090" or more to even be "deep cycle"...(0.090" is about the thinnest....typically 0.125" TO 0.150"....all the way up to 0.260" thick....the thicker the positive plate, generally the more life-cycles)... and the plate chemistry is also different....so-called "real" / "true" deep cycle batteries will generally have lead-antimony plates (rather than the lead-calcium plates), as this also increases the plate life-cycle (as well as increases its strength)....
And, note that lead-antimony plates off-gas significantly more than the more common plates....and consequently they have higher water loss / need to be "watered" more often....(and, you will almost always see "HydroCaps" or some other water-miser-type of cap, on them...to reduce the need for watering often...)
Further, be aware that these lead-antimony plate cells will generally have a slightly lower cell voltage....a maximum of 2.1vdc per cell @100% SOC....so the fully charged, resting voltage of these batteries (n "12vdc" configuration) is a max of 12.6vdc...and sometimes only 12.5 to 12.55...



4) As I wrote earlier, there is a lot more to all of this....and if you want to delve further, have a look at some of these threads...

Post#26 here...
http://www.cruisersforum.com/forums/...s-62379-2.html


Post#50 here...
http://www.cruisersforum.com/forums/...-110930-4.html


Post#39 here...
http://www.cruisersforum.com/forums/...-153023-3.html


5) Remember that your batteries are only one part of your on-board energy system....and understand that it IS a "system"....
If the "engineers" you hired are not clear about that....fire 'em now, and hire someone that is clear about this...
Solar-charging, energy-use / conservation, power-distribution, refrigeration insulation, sail-plan / sail-trim (for auto-pilot power consumption), engine alt / regulator, genset(?), towed-water-gen / wind-gen, lighting, etc. etc. etc....are all part of your on-board energy system...
Spec'ing / buying one part of the system, without considering the entire system as a whole is futile effort, and one that usually ends with money wasted and unnecessary frustration...


This is a rather important point, and one that is often over-looked (until it is too late)....and while I probably should've lead-off with this info, most would not have read thru the facts above, if I had...




Hope this helps...

Fair winds..

John

[barnakiel]

I never wire up EXCEPT if the physical size of the units makes then impossible to manage. Otherwise, if the boat is a 12V boat, stick with 12V batteries.

On my ex-(employer's) boat the boat was 24V wired up from 6V units. OMG.

You can't help some people's golf cart mentality.

b.

[ramblinrod]

Originally Posted by barnakiel

I never wire up EXCEPT if the physical size of the units makes then impossible to manage. Otherwise, if the boat is a 12V boat, stick with 12V batteries.

On my ex-(employer's) boat the boat was 24V wired up from 6V units. OMG.

You can't help some people's golf cart mentality.

b.

Ah, the voice of reason. What a breath of fresh air. ;-)

[john61ct]

Originally Posted by ka4wja

3) As for what is "deep cycle"?? Well, I don't want to get into an argument, but there are real engineering criteria to use here...

Yes there are, another excellent post, thank you! And just like beauty, even if it is a judgement call where you draw the line, doesn't mean the concept isn't valid.

For me, a trusted vendor's claim, backed up by data sheets of 800+ cycles at 50% would suffice. Since the Sam's Club/B+ Duracells are so crazy good value, I'll include them just on East Penn's reputation, plus the thousands of good longevity reports even from those admitting to chronic abuse.

Originally Posted by barnakiel

On my ex-(employer's) boat the boat was 24V wired up from 6V units.

Absolutely nothing wrong with a (1P)4S 24V system, except lack of redundancy, which in a House bank (way I do it) is not critical.

Originally Posted by ramblinrod

the responses are twisting in the wind every which way from Sunday. "I didn't post that", but later, "Yes I really did mean that." It's just nonsense gibberish. Especially after declaring in a post long ago in the thread, "I'm not going to argue".

I have never argued against redundancy, so if that is important for the design, then 2P4S is even better.

Originally Posted by ramblinrod

12 V batteries are available in pretty much every size imaginable from many different manufacturers.
...
But certainly, very reliable 12 Volt DC batteries of pretty much any form factor are available if one is will to pay a premium for higher quality.

So if I wanted a 1500+AH true deep-cycling bank, what models would you recommend?

[a64pilot]

Just out of curiosity, why do you think 36V and I think 48V Golf carts use 6V batteries?

[Bleemus]

Sigh . . .

[ramblinrod]

Originally Posted by john61ct

So if I wanted a 1500+AH true deep-cycling bank, what models would you recommend?

Can't answer that with the limited info provided; options are virtually endless.

First, I would advise that there is no such thing as a "True Deep-Cycle" battery. There are "Deep Cycle" batteries of varying design, quality, and cost.

Second, I would ask a whole bunch of questions about your boat, your electrical system, and how you intend to use it.

Third, I would make a recommendation, providing good, better, and best options, so you could pick a solution that best meets your performance needs and budget.

[ramblinrod]

Originally Posted by a64pilot

Just out of curiosity, why do you think 36V and I think 48V Golf carts use 6V batteries?

Well, based on very limited research and guesses...

6 Vdc FLA batteries are not new, they have been around for about 150 years.

Golf cars are currently manufactured in electric and gas powered versions.

Of the electric versions, many are operated by 6 Vdc batteries and some by 12 Vdc batteries.

Far more gas powered are sold than electric.

As to why 6 Vdc battery powered golf cars are predominant for electric powered, my best guess is that the first golf cars were designed when 6 Vdc batteries were most prevalent.

The golf car market was miniscule.

The automobile, farm machinery, and boating industry switched and standardized on 12 Vdc negative ground.

Perhaps because the golf car industry was so small, and not affected / governed by the standards of the other industries, stayed with the original 6 Vdc design for the most part, rather than change designs to 12 Vdc for the wiring economy, like the bigger industries.

[john61ct]

Originally Posted by ramblinrod

Can't answer that with the limited info provided; options are virtually endless.

My point is the options are much **more** endless using (the **much** more available within the true deep cycle niche) 6V and 2V building blocks.

All the other "use case" issues are irrelevant once I say I want 1500AH in FLA and as many 50% cycles as my money can buy.

Putting 15 cheap starter or pseudo-deep "dual use" 12V in parallel would be absurd, I'm sure you agree.

So let's say my budget is $2500, maybe 3+K - not too high end, middle of the road for true deep cycle. Assume retailer of your battery model is within driving pickup distance, no delivery or core charges needed.

Each battery (box with terminals) to be under say 80 lbs to prevent hernias. Never mind batt box dimensions.

So, specific 12V models with sample pricing please, and ideally life cycle vs DoD data.

Others contributing 2V or 6V based ideas would be most welcome.

Doing this with the cheapest true deep cycle, Sam's Club Deka/Duracell GC2, would be 7P2S at around $1,400.

So, obviously double the budget should give much greater longevity, and IMO less redundant paralleling.

[ramblinrod]

Originally Posted by john61ct

My point is the options are much **more** endless using the much more available 6V and 2V building blocks.

All the other "use case" issues are irrelevant once I say I want 1500AH in FLA and as many 50% cycles as my money can buy.

Putting 15 cheap 12V starter or pseudo-deep "dual use" in parallel would be absurd I'm sure you agree.

So let's say my budget is $2500, maybe 3+K - not too high end, middle of the road for true deep cycle. Assume retailer of your model is within driving pickup distance, no delivery or core charges needed.

Each battery (box with terminals) to be under say 80 lbs to prevent hernias. Never mind batt box dimensions.

So, specific 12V models with sample pricing please, and ideally life cycle vs DoD data.

Others contributing 2V or 6V based ideas would be most welcome.

Doing this with the cheapest true deep cycle, Sam's Club Deka/Duracell GC2, would be 7P2S at around $1,400.

So obviously double the budget should have a much greater longevity, and IMO less redundant paralleling.

First of all, you are wrong suggesting that use case issues are irrelevant. For all we know, you could be a pompous know-it-all, who doesn't have a clue what he needs and would be far better served with something other than asked for.

Even if you do have a decent handle, placement and compartment size on boat will have a bearing on the model selections. What are your charging systems? Can they even handle that much capacity? This all has to be reviewed.

If you ignore a whole bunch of stuff and assume it will all just fit and work, then...

8 x Rolls T12 250s would be a good choice. 50% DOD would give you about 1350 "Rolls" lab cycles.

It would be about US$3500, but you said you wanted the best.

That would give you 1600 A-hrs to start, and you'd still have 1400 A-hrs with one shorted battery isolated. No need for carrying a spare cell or having a DC-DC converter. Weight per battery is 50% higher than requested but that is part of what makes them so good. Treat them well, buy a new bank in 10 years, and get about 10% back in core for the old ones.

10 year cost = $US 3500 - 350 = $3150

Cost per year = $315.00

Or you could buy 15 x Deka Grp 27 DC. That would give you about 300 Deka lab cycles, but lighter per battery weight. This would cost about US$1500 and give you 1500 A-hrs, dropping to 1400 A-hrs with one isolated shorted cell, no additional equipment needed. Treat them well, buy a new bank in 4 years, and get about 10% back in core for the old ones.

4 year cost = $1500 - 150 = $1350.

Cost per year = $337.50

You outlay way less up front, and if you make 5% / yr on the savings, you are way ahead buying the Grp 27 DCs (if you don't consider the value of your time for battery replacement).

When you do need to replace a battery, pick one up at any port, rather than trying to arrange hazardous materials shipment half way round the world to some deserted island.

The last thing I would recommend is a string of 6 x 2 Volt cells. One goes down and you're dinked, unless you carry a spare cell (more money) which hopefully you are keeping charged some how, or a DC-DC converter (even more money). Pretty ridiculous when you really think about it.

[john61ct]

Yes for the Nth time I have agreed some redundancy is good, that's not in dispute AFAIC.

Rolls is obviously beautiful, except I would need to pay for the backbreaking labor, and I'd bet going lower voltages gives even more cycles, so likely more (too?) expensive.

The Deka suggestion is crazy expensive for 300 cycles, not even true deep cycling IMO. Automotive starter form factors generally like that.

Deka is great, but I think I'd rather look at Crown and Trojan if Rolls comes out too pricey in such a better format.

Plus paralleling x15 really does add a lot of unnecessary points of failure interconnects.

Both vendors would give reasonable per-batt weight, redundancy and lower cost with a 6V or 2V base unit.

I've also found notes that the lower the voltage, the **better** the cooling factor, which I believe you agreed is important?

[ramblinrod]

Originally Posted by john61ct

Yes for the Nth time I have agreed some redundancy is good, that's not in dispute AFAIC.

I see you post this here but in other posts suggest or support only a series string. I am a bit confused by your conflicting, diametrically opposed positions, depending on the post.

Rolls is obviously beautiful, except I would need to pay for the backbreaking labor, and I'd bet going lower voltages gives even more cycles, so likely more (too?) expensive.

Replacing batteries of any type is hard work. As with any type of work, use the correct tools for the job.

Nope, wrong again a Rolls S-1450 (2Vdc 1500 A-hr) spec life cycles and weight are about the same.

There is no reason to believe lower voltage contributes to longer life.

The Deka suggestion is crazy expensive for 300 cycles, not even true deep cycling IMO. Automotive starter form factors generally like that.

Nope, as illustrated in the post you are responding to, the Deka suggestion is actually much lower cost initially and per year.

Deka is great, but I think I'd rather look at Crown and Trojan if Rolls comes out too pricey in such a better format.

Whatever turns your crank. (Har, weight, we're talking house bank ;-).

Again as I posted, there are numerous options and various quality and price points in every major battery manufacturers 12 Vdc range.

Plus paralleling x15 really does add a lot of unnecessary points of failure interconnects.

Not unnecessary. Absolutely necessary for them to work if that is the form factor and battery weight that meets your needs.

I would personally choose a 12 Vdc battery with higher A-hr rating to reduce the number of connections, at the expense of increased weight. As with every other decision on a boat, there are conflicting elements that require compromise.

If you wanted a per battery weight of 10 pounds, and still 1500 A-hr capacity, there would be a lot more connections.

Remember, you set the criteria and suggested there were no other considerations. Now you are stating that the number of connections is important to you. See? We should have talked about a number of issues BEFORE attempting to select a specific model.

Both vendors would give reasonable per-batt weight, redundancy and lower cost with a 6V or 2V base unit.

Isn't "reasonable" a weasel word in this thread. (I don't believe considering reason is unreasonable, but apparently others do.)

Every major vendor has a large offering of 12 Vdc batteries that one can pick the form factor, weight, capacity, quality, and cost, that best suits ALL of their requirements.

No, the battery itself does not afford any redundancy. When it fails, it fails. It is the connection configuration that affords natural redundancy. A single series string offers none. 12 Vdc batteries in parallel provide a lot, the more the merrier, by simply isolating the defective battery. Hmmmm, I've posted this a number of times, you declare in this post you are all for redundancy, but you still don't seem to get it.

I've also found notes that the lower the voltage, the **better** the cooling factor, which I believe you agreed is important?

Yes, heat dissipation is important.

I personally believe your statement is total horse caca. Please share your source with us that lower voltage contributes to cooling.

Everything else equal, the chemical reaction is the same. For a specific form factor, the amount of heat generated while charging or discharging will be based on the load and the number of watts required to satisfy it. If comparing a 6 x 2 Vdc string to an 8 x 12 Vdc parallel bank, the latter will run way cooler, assuming proper battery compartment ventillation. Fewer watts per battery.


For example, if the load is 1 kW, each battery in the 6 x 2 Vdc series string is supplying 166W = 28A.

In contrast, that same load applied to a 8 x 12 Vdc parallel bank, demands 125 W = 10 A per battery.

Everything else equal, guess which bank is gonna run cooler and last longer?

Answer: The 8 x 12 Vdc parallel bank.

Interestingly, the 15 x grp 27 solution, would run coolest, everything else equal, (including batteries not being stacked in height).

Hmmm, I guess there is a little more to selecting a battery model than just A-hrs and weight. Oh weight (Har Har) a minute that is another thing I stated and you disagreed with.