Wiring In Series (pro vs con)

[s/v Jedi]

Originally Posted by ramblinrod

You have every right to believe who and whatever you want. You support the position of some posters because you agree with them and don't those you don't. Me too.

No it doesn't work like that. You act like it's just a difference of opinion but it isn't: it is facts and laws of nature that you choose to ignore. It has nothing to do with who I agree with in this thread because I agree with the science behind it, just like some other posters and that is what put us on the same line. It is you who oppose us and thus widely accepted principles of electrical engineering.

About engineers vs electrical technicians: where I come from, the techs listen to, and are guided by the engineers. What you call "electronics technician" is what I call a field engineer who installs electronics. Electronics engineers, which is (was) my primary position, design the schematics and circuit boards that are inside the electronics that you install. The knowledge level is hugely different, 5 years extra study and in many countries another year of apprenticeship. I believe in the US it is college vs university but I understand little from the US educational system and agree with you that some titles are given away too easily there.

Anyway, like Tasso wrote, you can't argue with the science he put forward so you keep ignoring that and rambling on about how good 12V batteries in parallel are. Like Tasso, I agree it's probably cheaper and that is a good reason for many to go that way.

When you check out high end yachts, they come with 24V house banks configured with 12x Sonnenschein 2,500Ah gel cells in series. They don't even take a spare and first maintenance is 20 years later

[rwells36]

This is the OP. I learned a lot more than I expected, so if this is the end of the string...well, no objection here

[Tasso]

Originally Posted by rwells36

In order to get around the backorder of a particular battery supplier for their 12v product I am considering the purchase of their 4v products which have no backorders and then wiring three (3) of these 4v 450Ah in series to achieve 12v. However, I desire to have a total of 900Ah at 12v (not 24v). Is this possible? If so, how?

This is amusing but I can't remember if anyone actually answered your question...

To use the batteries you suggest you will need 6 of the 450Ahr batteries. They will need to be configured in strings of 3 to get to 12v. You can parallel each 4v pair or two 12v series strings of three - your choice.

Sorry for messing this thread up. You posted a simple question. I guess asking pros and cons is dangerous.... I had no idea either...

[socaldmax]

Originally Posted by a64pilot

I brought up golf carts, because there are tens of thousands of electric golf carts produced yearly, They are not a small manufacturing concern at all, and their use of a battery bank closely mimics our boating use, boats being a tiny fraction of battery consumption compared to golf carts.
Golf carts would use the most economically viable battery available consistent with long life period, and that is the abundant golf cart 6V battery.
For an idea of production volume
https://www.golfcartsforsale.com/blo...er-golf-carts/

You know that, the rest of us know that, but RR simply doesn't want to admit it. My experience has been that "12v deep cycle" batteries are much more expensive than GC batteries, with lower capacity than GC batteries. In a case like this, you just stop arguing, it doesn't do any good.

[john61ct]

But if you deny the huge difference between

Pseudo-deep-cycle batteries as sold through auto and mass consumer retail

and

true deep cycle batteries, which are more commonly sold in lower voltage cells

then it's easy to kid yourself that the more convenient and less expensive option is "just as good".

And of course at the low end of AH per day consumed, and number of days away from shore power, for 90% of all the (small) boats out there, the latter may well be "good enough".

[camel2012]

Originally Posted by Tasso

With two batteries in parallel - one with a shorted cell - say one at 12v one at 10v - the battery with the higher voltage will provide full current in an attempt to bring two batteries to 12v. The current will only be restricted by the internal resistance of the batteries. In this prolonged high current situation both batteries will get quit hot. Temperature will depend on the batteries and the bank configuration.

This scenario will never happen in a series configuration.

Melt-down is the most likely result and this is a common problem. In fairness explosion or fire are less likely but remain a possibility - especially in large parallel banks.

Your boat. Your life.

I'm just providing info to those who care. I don't understand why anyone in the industry would not want to acknowledge this fact.

When I'm out of sight of land - I don't care what batteries are easiest to purchase. I just want to be as safe as possible.

This is not consistent with physics and reality, I have tested situations like this repeatedly and the result is far more benign that you could are imagining. Worst case is switching into a shorted cell battery or bank, which causes a few seconds of current transfer then the two battery voltages balance with very little ongoing current transfer. If a single battery in a parallel bank were to develop a short, the result is even more benign.

I asked earlier how many people have had a shorted cell, and from the limited responses I got I don't see situations where (a) high quality batteries were (b) properly maintained and (c) not exceeded their expected useful life...where a short has developed. Redundancy can take many tracks and while I'm not personally a fan of a single series bank I can appreciate the line of thinking.

[camel2012]

Originally Posted by socaldmax

You know that, the rest of us know that, but RR simply doesn't want to admit it. My experience has been that "12v deep cycle" batteries are much more expensive than GC batteries, with lower capacity than GC batteries. In a case like this, you just stop arguing, it doesn't do any good.

I would strongly disagree. Golf carts and boats have completely different outcomes if a cell or battery fails. Boating can be a life and death proposition given the potential circumstances. Getting stuck with no power on the 12th hole is no equivalent. Every aspect of a golf cart is focused on cheapest annual cost.

Use what you want, but the golf cart application equivalency argument falls very flat.

[mitiempo]

Originally Posted by camel2012

I would strongly disagree. Golf carts and boats have completely different outcomes if a cell or battery fails. Boating can be a life and death proposition given the potential circumstances. Getting stuck with no power on the 12th hole is no equivalent. Every aspect of a golf cart is focused on cheapest annual cost.

Use what you want, but the golf cart application equivalency argument falls very flat.

Certainly the golf courses want low cost. They want it for batteries that are cycled to 50% SOC or lower daily. A 12 volt pseudo deep cycle battery will not last nearly as long in that application as a GC will.

A large number of offshore cruisers have banks of golf cart batteries and find them an excellent choice for their cycling ability, ease of handling, availability anywhere worldwide, and relative low cost. Some have 2 in series but most have 4 or more in series/parallel.

Those that stick close to home can do well with a couple of group 27's which are on a shore power charger the bulk of the time.

[ramblinrod]

Originally Posted by s/v Jedi

No it doesn't work like that. You act like it's just a difference of opinion but it isn't: it is facts and laws of nature that you choose to ignore.

).

Please show me the "facts" or "laws of nature" that I have ignored in this thread.

[john61ct]

1. Your maintaining that just because the distinction between true deep cycling and pseudo DC dual purpose batteries isn't a bright clear publicly agreed line, the distinction doesn't exist and isn't important.

[Tasso]

Originally Posted by camel2012

This is not consistent with physics and reality, I have tested situations like this repeatedly and the result is far more benign that you could are imagining. Worst case is switching into a shorted cell battery or bank, which causes a few seconds of current transfer then the two battery voltages balance with very little ongoing current transfer. If a single battery in a parallel bank were to develop a short, the result is even more benign.

I asked earlier how many people have had a shorted cell, and from the limited responses I got I don't see situations where (a) high quality batteries were (b) properly maintained and (c) not exceeded their expected useful life...where a short has developed. Redundancy can take many tracks and while I'm not personally a fan of a single series bank I can appreciate the line of thinking.

So I think I was clear that this has not happened on my boat. I have talked to two people that have seen it. One an owner - one a technician who resolved one. In both cases the scenario was actually quite subtle - detection was though a "weird smell" - well into a battery meltdown.

I'd be willing to elaborate (without naming names) but as the OP has requested we end this - I suggest someone open a thread on battery failures and we could give interested parties an overview of what has actually been seen...

[ramblinrod]

Originally Posted by john61ct

1. Your maintaining that just because the distinction between true deep cycling and pseudo DC dual purpose batteries isn't a bright clear publicly agreed line, the distinction doesn't exist and isn't important.

I have clearly stated that there is really no such thing as a "True Deep Cycle Battery", but rather there are various degrees of quality of batteries marketed as "Deep Cycle" batteries, and what this means to the boater.

That's a fact.

I have not ignored it at all, exactly the opposite, I've posted a lot on this subject, that I do not support these terms some are using, with the reasons why.

That's a fact.

[Rick]

Incorrect Teddy. A shorted cell in any One battery can destroy either a series or parallel Bank or discharge it before you can do anything about it. Buy a parallel Bank comprising batteries from the same manufactured dates and batches. Series connected batteries require purchasing of connectors and wires not required for parallel connections with today's technology there is no reason to have series connected batteries for 12-volt systems

[TeddyDiver]

Originally Posted by Rick

Incorrect Teddy. A shorted cell in any One battery can destroy either a series or parallel Bank or discharge it before you can do anything about it. Buy a parallel Bank comprising batteries from the same manufactured dates and batches. Series connected batteries require purchasing of connectors and wires not required for parallel connections with today's technology there is no reason to have series connected batteries for 12-volt systems

You mind to tell us how series bank could be destroyed by a shorted cell?

[rwells36]

Originally Posted by Rick

Incorrect Teddy. A shorted cell in any One battery can destroy either a series or parallel Bank or discharge it before you can do anything about it. Buy a parallel Bank comprising batteries from the same manufactured dates and batches. Series connected batteries require purchasing of connectors and wires not required for parallel connections with today's technology there is no reason to have series connected batteries for 12-volt systems

Rick, there are reasons for others that may not be reasons for you.