Wiring In Series (pro vs con)

[Tasso]

Originally Posted by ramblinrod

For FLA battery banks this is not a serious concern. The internal impedance is high enough that, even with a shorted cell, the current flow from the good battery is not sufficient to cause any serious harm.

I have seen otherwise. I do not consider trusting my life to the internal resistance of my batteries a good life choice.

[Tasso]

Originally Posted by ramblinrod

To not parallel FLA batteries due to the risk of a shorted cell, is either a misunderstanding of the risk, or an irrational phobia. ...

I wonder if you have ever been on a multi-day passage. On the open ocean one acquires all sorts of "irrational phobias". I'm happy to admit this but I expect to live longer by showing respect for situations that can kill me...

Originally Posted by ramblinrod

If it could, it would be happening all over the world at an alarming rate, because there are millions and millions of vessels configured this way. It isn't.

Battery melt-downs are not that uncommon.

As I said previously - I only connect batteries in parallel for emergency starts. I am happy in my delusional world...

[ramblinrod]

Originally Posted by Tasso

I wonder if you have ever been on a multi-day passage.

Yes, many. Frankly to me electrical safety is equally important sitting at the dock as it is 1000 miles from nowhere.

On the open ocean one acquires all sorts of "irrational phobias".

Ok, as long as we understand what it is.

I'm happy to admit this but I expect to live longer by showing respect for situations that can kill me...

I show respect for things that can kill me. Any kind of boating itself incurs all kinds of risks. FLAs in parallel, negligible.

Battery melt-downs are not that uncommon.

OK, please cite some reputable source indicating how many FLA battery meltdowns happen, as a result of a parallel battery feeding one with shorted cell.

There are millions and millions of boats configured this way. If it's not more likely than being conked on the head by space junk, I'm OK with that.

[john61ct]

Originally Posted by GrowleyMonster

All series. Before, I was so stuck on 12v thinking that it nearly had to be beaten into my head that 12v would totally suck for propulsion.

We really do need to specify the context for these discussions, electric propulsion is a **completely** different use case from normal House loads.

Same with huge boats running loads like A/C, electric cooking, (sauna FFS!!!).

And on the other end, saying "most boats, millions of boats" "internal combustion forklifts" when obviously those are Starter usage.

That kind of wild use-case variability derails the core issue being discussed here. Which is of course a derail from OP, let's at least stick to one derail at a time.

My main takeaways so far:

Some redundancy is good, at a minimum cranking and keeping essentials to navigation going long enough to get back to civilisation.

Personally a larger true deep cycle Starter/Reserve would be "enough", but not matching what I consider normal House sizes, two equal banks switching roles sounds great, but with lead chemistries, you get so much more effective capacity with putting more of your eggs in one basket.

If you only put non-essential loads on House, I don't see the need for redundancy there, and that then becomes the backup bank for all the critical devices.

I completely reject the "no serial, only use 12V batteries" idea, and am also very skeptical of paralleling in and of itself adding danger.

But if it does, then fusing between paralleled 12V serial strings seems a good idea, as long as resistance isn't an issue.

[TeddyDiver]

Originally Posted by john61ct

But if it does, then fusing between paralleled 12V serial strings seems a good idea, as long as resistance isn't an issue.

There lies the caveat. To be safe the fuses had to be for reasonably low current and that works against having a big paralled battery bank unless the charging source is low current too and no bigger loads either. So it's reasonable solution for an occasional weekend sailor. Enough juice for a couple of days and five days connected to low current charger. That's also how most boats are used at best so it's no wonder most production boats are made that in mind.
Full time long distance cruising is a rare thing among boaters..

BR Teddy

[ramblinrod]

Originally Posted by TeddyDiver

There lies the caveat. To be safe the fuses had to be for reasonably low current and that works against having a big paralled battery bank unless the charging source is low current too and no bigger loads either. So it's reasonable solution for an occasional weekend sailor. Enough juice for a couple of days and five days connected to low current charger. That's also how most boats are used at best so it's no wonder most production boats are made that in mind.
Full time long distance cruising is a rare thing among boaters..

BR Teddy

The fuse on the output of a series string or parallel house bank needs to limit current to the maximum the conductors can safely carry. That's it. If the maximum load the bank will see is 100 A, and the wire can handle 100 A, one uses a 100 A fuse.

[TeddyDiver]

Originally Posted by ramblinrod

The fuse on the output of a series string or parallel house bank needs to limit current to the maximum the conductors can safely carry. That's it. If the maximum load the bank will see is 100 A, and the wire can handle 100 A, one uses a 100 A fuse.

To protect the wire yes, but very idea is to prevent runaway battery meltdown. Quess twice what's left of the batteries with 1.2kW warm up for.. how many you said there were in parallel? 6? so 5 feeding one that's five hours all in a smallest possible battery box. That of course is the worst case scenario excluding battery explosion but anyways..

BR Teddy

[john61ct]

Originally Posted by TeddyDiver

Full time long distance cruising is a rare thing among boaters.

Well let's put in the design brainstorming where it's needed, true deep cycling, multiple mobile charge source inputs, maybe very rarely seeing the mains grid.

So let's say we have a 4S4P bank in LiFePO4, each 3.2V cell @ 100AH ==> nominal 12V @ 400AH

Note I've chosen super-low resistance LFP, so there's no doubt about the huge current flow that would result from a dead short or internal cell failure.

Lets also not debate here "series first vs parallel first", say I need S then P, e.g. I want 12V 4-blocks for flexibility, each in their own strap-box so I can take one or more ashore for camping.

If I anticipated occasional high charge rates /bursty discharge, I put say a 600A fuse on the whole bank, would I need the same between each 12V block of four?

Or would say 200A or 300A fuses between 12V blocks give better protection?

This is assuming the fuses also have very low resistance.

[Tasso]

Originally Posted by TeddyDiver

To protect the wire yes, but very idea is to prevent runaway battery meltdown. Quess twice what's left of the batteries with 1.2kW warm up for.. how many you said there were in parallel? 6? so 5 feeding one that's five hours all in a smallest possible battery box. That of course is the worst case scenario excluding battery explosion but anyways..

BR Teddy

Actually the remaining non-shorted cells contribute 10v of emf to the circuit - the actually power dissipation is 200 watts plus whatever your charging system is throwing at it. Bad time to connect one of those high output alternators...

My engine needs 150 amps to crank - so I installed 200 amp breakers with oversize cable to minimize voltage drop...

Happy with my two series GC2's in each isolated bank. My dual solar charger distributes the total solar power to whichever isolated bank needs it automatically. Haven't seen a larger version of this unfortunately...

The industry is reflected by Rod's comments. Just not on my boat. Had an interesting chat with Nigel Calder on this. Lots of people are installing temperature probes which seems to be the best option.

In fairness explosion is rare - fires are usually caused by secondary issues but paralleled configuration just exacerbates it - contributing extra current to a bad connection say.

[ramblinrod]

Originally Posted by TeddyDiver

To protect the wire yes, but very idea is to prevent runaway battery meltdown. Quess twice what's left of the batteries with 1.2kW warm up for.. how many you said there were in parallel? 6? so 5 feeding one that's five hours all in a smallest possible battery box. That of course is the worst case scenario excluding battery explosion but anyways..

BR Teddy

I really want to respond to this, but alas, I ma too busy with "critical to launch" work on boats for the next couple of days. I'll be back.

The short of it is, you can put any number of 12 Vdc FLA batteries in parallel, without individual fuses (not a requirement of any marine electrical standard), and if a cell shorts, one will know immediately. They can lolligag around for hours, days, maybe weeks, before anything remotely bad may start to happen. To prevent any issue, flick a switch to isolate the defective battery until you fix it, at your leisure, inexpensively.

True, if one goes for more exotic, expensive batteries with higher acceptance rates, this time will be shortened, especially with Lion. Put dangerous batteries on your boat, well, it can be dangerous.

With 2 Vdc cells, there is likely a pretty significant alternator or charger, and the same danger is present, because as we all know, the charger, an even higher voltage source than a parallel battery, has to be mounted in parallel.

[Pete7]

Think it is also worth remembering that the vast majority of boats both sail and motorboats are probably fitted with a pair of 12v batteries, one engine and one house. Some yachts may have a few more batteries for a bigger house bank, but they are still 12v.

Why? because its cheap to install by the manufacturer and simple to maintain by the owner. All that happens is once ever 2 - 3 years he goes along to the chandlers or folk like Ramblinrod and buys a new battery, problem solved.

If he keeps the boat more than 3 years which is unlikely, then he may wonder why the battery only lasts 3 years when the ones in his car last 5 - 6 years, but a cheap leisure rated sealed for life 100AH battery isn't that expensive so why bother with all that extra charging malarkey?

Those with golf cart 6v batteries are in the minority, those with 2v batteries are probably on the the endangered species list in terms of numbers.

Those that participate in forums and owners associations will learn that their are other ways of doing things and some worth incorporating in their own boat as sort of half way point depending on a balance of cost, time and effort involved.

for us with a KISS approach and a budget, 2 x 12v deep cycle batteries and lots of solar meets our needs in a cost effective way and is easily maintained or replaced.

Pete

[s/v Jedi]

Pete, (I'm using your name but really address everybody in general so don't take this personally) those of us saying a series string is best completely agree with a 12V battery. For us, that is 6x 2V cells in series, which is exactly what it is. It does not matter if you have one 12V battery or 6x a 2V cell in series. We can argue about external vs internal inter-cell links but as long as the 12V battery has the capacity and features required, it's golden.

The problem starts when people put batteries in parallel. The battery with the highest voltage discharges into the others until they are equal. They are never equal and there always is a discharge process going on which is one disadvantage of the setup but the real trouble starts when one battery gets an internal short. The other batteries start discharging into that failed battery until the whole bank is flat and worthless. Even when you start a generator or plug in shore power, most battery chargers won't even start charging and the only way out is to disconnect every battery and see if any recover enough to be recharged.

With a series string this will never happen, it is the royal setup just like a single 12V battery. The only reason to divert is for lack of budget or when you need more capacity per cell than what is available.

Now, we have nothing against people choosing to not spend the higher cost of a big series bank; a G31 bank of Firefly batteries is pretty awesome (not cheap either though) but just don't try to fool others and yourself into believing it is the best setup, because it ain't.

When people start buying the Walmart or Cosco "Duracell" specials and stating it is the best bang for the dollar then they fool themselves. There is no Costco in Vanuatu and even if you have access to those, the time dealing with failures and replacements counts as cost as well. I believe that when you install a bank of Firefly or Lifeline batteries that you are better off financially in the end. If you want cheaper then go for a cheaper technology but of the same quality level, like a Trojan flooded battery instead of AGM.

Also: it doesn't matter how many boats have a parallel bank, that does not make it a better setup. Even when Madonna tells you, it still isn't better. That's the thing with science, it rules

Do problems occur often? no, I only had a parallel battery explode on me once in the 40 years of using them. But I'dd rather not have the experience and I was lucky the acid didn't hit me in the face.

"New" technology like AGM and LiFePO4 allow separate banks again where you use one and have another ready to go while being disconnected for long periods. That's the way to go. Somebody wrote that they have LFP packs aboard ready to take on camping trips. When we leave our boat in storage I have my solar keeping the house bank up but the starting batteries stay disconnected and are at 85% charged when I return 6 months later. I connect them and start the engine.

About taking a spare 2V cell: contrary to a parallel bank, you can always replace a cell in a series bank: even when the bank is 5 years old, you can replace one cell with a new one. This is why it makes sense to buy an extra cell: after so many years, you look at the weakest cell you have and swap it for the spare cell to revive the bank while keeping the option of a spare. I have seen boats with a series bank that is 20 years old and still going, not needing replacement.

A higher voltage is another great idea. A 48V bank is great and I would have it if it wasn't for my windlass and electric winches. The rest can easily go on a DC-DC converter.

Originally Posted by Pete7

Think it is also worth remembering that the vast majority of boats both sail and motorboats are probably fitted with a pair of 12v batteries, one engine and one house. Some yachts may have a few more batteries for a bigger house bank, but they are still 12v.

Why? because its cheap to install by the manufacturer and simple to maintain by the owner. All that happens is once ever 2 - 3 years he goes along to the chandlers or folk like Ramblinrod and buys a new battery, problem solved.

If he keeps the boat more than 3 years which is unlikely, then he may wonder why the battery only lasts 3 years when the ones in his car last 5 - 6 years, but a cheap leisure rated sealed for life 100AH battery isn't that expensive so why bother with all that extra charging malarkey?

Those with golf cart 6v batteries are in the minority, those with 2v batteries are probably on the the endangered species list in terms of numbers.

Those that participate in forums and owners associations will learn that their are other ways of doing things and some worth incorporating in their own boat as sort of half way point depending on a balance of cost, time and effort involved.

for us with a KISS approach and a budget, 2 x 12v deep cycle batteries and lots of solar meets our needs in a cost effective way and is easily maintained or replaced.

Pete

[ramblinrod]

Originally Posted by s/v Jedi

Pete, (I'm using your name but really address everybody in general so don't take this personally) those of us saying a series string is best completely agree with a 12V battery. For us, that is 6x 2V cells in series, which is exactly what it is. It does not matter if you have one 12V battery or 6x a 2V cell in series. We can argue about external vs internal inter-cell links but as long as the 12V battery has the capacity and features required, it's golden.

The problem starts when people put batteries in parallel. The battery with the highest voltage discharges into the others until they are equal. They are never equal and there always is a discharge process going on which is one disadvantage of the setup but the real trouble starts when one battery gets an internal short. The other batteries start discharging into that failed battery until the whole bank is flat and worthless. Even when you start a generator or plug in shore power, most battery chargers won't even start charging and the only way out is to disconnect every battery and see if any recover enough to be recharged.

With a series string this will never happen, it is the royal setup just like a single 12V battery. The only reason to divert is for lack of budget or when you need more capacity per cell than what is available.

Now, we have nothing against people choosing to not spend the higher cost of a big series bank; a G31 bank of Firefly batteries is pretty awesome (not cheap either though) but just don't try to fool others and yourself into believing it is the best setup, because it ain't.

When people start buying the Walmart or Cosco "Duracell" specials and stating it is the best bang for the dollar then they fool themselves. There is no Costco in Vanuatu and even if you have access to those, the time dealing with failures and replacements counts as cost as well. I believe that when you install a bank of Firefly or Lifeline batteries that you are better off financially in the end. If you want cheaper then go for a cheaper technology but of the same quality level, like a Trojan flooded battery instead of AGM.

Also: it doesn't matter how many boats have a parallel bank, that does not make it a better setup. Even when Madonna tells you, it still isn't better. That's the thing with science, it rules

Do problems occur often? no, I only had a parallel battery explode on me once in the 40 years of using them. But I'dd rather not have the experience and I was lucky the acid didn't hit me in the face.

"New" technology like AGM and LiFePO4 allow separate banks again where you use one and have another ready to go while being disconnected for long periods. That's the way to go. Somebody wrote that they have LFP packs aboard ready to take on camping trips. When we leave our boat in storage I have my solar keeping the house bank up but the starting batteries stay disconnected and are at 85% charged when I return 6 months later. I connect them and start the engine.

About taking a spare 2V cell: contrary to a parallel bank, you can always replace a cell in a series bank: even when the bank is 5 years old, you can replace one cell with a new one. This is why it makes sense to buy an extra cell: after so many years, you look at the weakest cell you have and swap it for the spare cell to revive the bank while keeping the option of a spare. I have seen boats with a series bank that is 20 years old and still going, not needing replacement.

A higher voltage is another great idea. A 48V bank is great and I would have it if it wasn't for my windlass and electric winches. The rest can easily go on a DC-DC converter.

Well, as luck would have it, I'm stuck in a coffee shop waiting for rain to stop. (On my iPhone the worst POS to key in, so please excuse typos and strangeness.

I just can't believe all this nonsense about putting batteries in parallel being unsafe.

If one installs 6 high capacity 2Vdc cells in series, the charger is connected in parallel. For a 1200 A-hr bank of high acceptance rate batteries,
What kind of charger do you have, a Promariner 12?
No that would be stupid, it would not take advantage of
The expensive high acceptance rate batteries, so instead, one puts
in a 200 A charger.

If a 2Vdc cell shorts, guess what, the charger is going to feed 200 A to that series string, which if unattended will boil dry and possibly melt down.

In comparison if one had 10 x cheap Deka Grp
27 DCs in parallel, the shorted cell battery acceptance is around 25 amps. It will take far longer for the charger to boil it dry and risk of meltdown is negligible.

Typically, the charger will be lower output, because more would be a waste the batteries can't except, so it just isn't capable of
Doing the damage a higher output
Charger feeding a high acceptance series
String can deliver.

So the truth of this whole matter is, cheap batteries in parallel are very safe. Expensive (high acceptance) batteries in any configuration,
Including a single series string ARE NOT.

[Tasso]

Originally Posted by ramblinrod

Well, as luck would have it, I'm stuck in a coffee shop waiting for rain to stop. ...

I just can't believe all this nonsense about putting batteries in parallel being unsafe.

If one installs 6 high capacity 2Vdc cells in series, the charger is connected in parallel.
...

The expensive high acceptance rate batteries, so instead, one puts
in a 200 A charger.

If a 2Vdc cell shorts, guess what, the charger is going to feed 200 A to that series string, which if unattended will boil dry and possibly melt down.

In comparison if one had 10 x cheap Deka Grp
27 DCs in parallel, the shorted cell battery acceptance is around 25 amps. It will take far longer for the charger to boil it dry and risk of meltdown is negligible.

Guess that you're stressed at the coffee shop - but your comments are a bit condensing.

We are not stupid. We just have a different opinion.

There are trade-offs for any configuration.

BTW - anyone with a 200 amp charger without temperature sensors for alarms and shut down is crazy!

[GrowleyMonster]

Originally Posted by john61ct

We really do need to specify the context for these discussions, electric propulsion is a **completely** different use case from normal House loads.

And I am talking about a house bank. Electric propulsion aside, a large series bank offers additional advantages as a house bank. Being able to loop a bad battery out of the system and still function normally, for instance. Electric propulsion is only the factor that made me realize this, getting me off the 12v or nothing mindset. It is not the only circumstance that makes it possible or practical or advantageous. Apparently I was unclear in my post.