Wiring In Series (pro vs con)

[Pete7]

Originally Posted by Tasso

This statement is false.

The biggest risk of melt-down, explosion or potential fire, occur from rapid discharge. Rapid discharge is more likely when batteries are connected in parallel. .

How? what increases the danger of parallel over series?

I can see a rapid discharge from a short of the positive cable on say the engine, but what else is going to give a rapid discharge to a pair of batteries?

Pete

[ramblinrod]

Originally Posted by Tasso

The biggest risk of melt-down, explosion or potential fire, occur from rapid discharge. Rapid discharge is more likely when batteries are connected in parallel.

When a dead short is placed across a battery, it will give up all of the current it can as fast as it can.

Very bad things are going to happen, instantly. It doesn't matter whether the bank is a series string or parallel bank or any combination.

According to ABYC - each branch in a parallel configuration should have fuse or breaker protection.

ABYC requires that a current limiting device be within 7" of the source (in this case, a battery or a battery bank).

Individual batteries in parallel do not have to be fused.

Please refer to ABYC E11, AC and DC Electrical Systems On Vessels, section 11.10 "Over current Protection" and show me where it states that parallel batteries must be fused.

You should realize when posting electrical advice that you may be putting others at risk.

I am fully aware of most electrical risks, and am very safety conscious.

I teach marine electrical seminars and perform vessel electrical inspections.

To understand the amount of potential energy in a battery - you can google "car battery arc welder"...

No need, I am already very familiar with the amount of potential energy in a battery, and have been for about 40 years.

1. Rapid discharge is dangerous.

3. Configurations that make it more likely should be avoided

.

Yes rapid discharge is dangerous. But your position is like claiming that bombs are dangerous, 1 stick of TNT on a boat is OK, but 2 is unacceptable.

Any battery configuration when dead shorted is extremely dangerous.

Don't dead short any battery bank or very bad things are going to happen.

Parallel banks are 100% ABYC and NFPA compliant.

If there was a significant safety advantage to single series strings over parallel battery configurations, I am confident that ABYC would not specifically illustrate parallel batteries as a valid marine battery bank configuration.

[ramblinrod]

Originally Posted by Tasso

No one is advocating leaving shore without at least two fully redundant banks.

Actually, a couple of posters throughout this thread have advocated having no parallel batteries in a house bank, just one series string.

It is very clear in post 142.

[TeddyDiver]

Originally Posted by ramblinrod

Actually, a couple of posters throughout this thread have advocated having no parallel batteries in a house bank, just one series string.

It is very clear in post 142.

I'm defineatly one But with some points to be taken into account.
Reasonably big starting battery as emergency backup when the house bank is 12v and consist of single 12v or two 6v batteries. Would have to cut some excess consumption but the necessary.
With house bank n x 2v (anything from 12v to 48v) and n x 6 (18v to 48v) subpanels connected with DC-DC converter to deliver 12v doesn't matter if you loose a battery, just have a good enough programmable charger or be smart running the generator until the faulty battery is replaced.
Besides running the electronics and lights via DC-DC converter provides better constant stream of electrons..

BR Teddy

[Pete7]

TD, have you thought of the additional cost to your plan. Whilst 24v battery chargers are readily available how about 36 or 48v? Oh sure by mail order etc but at what price and availability off the beaten track? Oh and how much is a large DC/DC converter? do you really need all that complication on a 35 ft yacht? we manage with very well with a KISS approach and 2 x 12v house batteries.

I can buy a 12v battery within walking distance of my boat on a Sunday morning, can't do that if I wired it with 2v and even 6v cart batteries would require some travel or mail order. Fine in your home port how about some foreign country were everyone wants a cut.

Pete

[Pete7]

Originally Posted by TeddyDiver

Besides running the electronics and lights via DC-DC converter provides better constant stream of electrons..
BR Teddy

Not in my experience. Presumably you are planning on having a DC/DC converter with a 12v output. Well my experience on a previous boat was that the electronics and fridge actually ran better on 24v or 27v when the alternator was running. The only item that couldn't run on 24v was the Icom VHF radio so that had a cheap 12v converter.

Pete

[B.Babs]

The relationship to be examined is load to cell ampere hour capacity at charge or loading rate.

one Groupe 27 115 ampere hour battery has the 20 hour loading rate equal to 5.75a. each of six cell is getting a 5.75a load.

two Groupe 27 115 ampere hour batteries for parallel have the 20 hour loading rate equal to 11.5a. each of 12 cell is still getting a 5.75a load.

the Groupe 27 has six cells each are 115 ampere hour in parallel two become 230 ampere hours of storage at 12V

a 230 ampere hour GC golf battery will have three 230 ampere hour cells. when put in series they make six 230 ampere hour cells making the 12v battery with 20 hour loading rate of 11.5a.

the loading rate to supply bank ampere hour capacity on the GC golf battery cell .05c

the loading rate to supply bank ampere hour capacity on the parallel Groupe 27 cell .05c

cells are maintaining the same work load with relation to cell capacity

.05c ‘ 5.75a equals the same percentage to capacity loading to a 115 ampere hour cell as 11.5a would be to the 230 ampere hour cell. both are equal to .05c

both batteries do work proportional to cell ampere hour capacity.

switch on a inverter and a 70a discharge loading to each battery. each cell is still proportional in loading to cell ampere hour storage

230 ampere hour parallel Groupe 27 with 70a makes .3c loading of cell
230 ampere hour GC golf with 70a makes .3c loading of cell

a 12v battery does not become half of the work of 6v or 2v when ampere hour capacity is the equal. the level of cell work is proportional with cell ampere hour capacity.

[Tasso]

Originally Posted by Pete7

How? what increases the danger of parallel over series?

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.

[s/v Jedi]

I really hope that people reading this are starting to realize that series connection is the better option and have learned to mostly ignore the ramblin going on here.
If your bank is only 12V, which is the most vulnerable setup for a failure of a cell as you lose 1/6th of your voltage, then you can still continue in several ways: if only back to the marina, switch over to your starting bank. Boats that push further have bigger starting banks as well: I have two Odyssey group 31 beasts that are more powerful than many house banks. But if you are on an off-shore passage, you can live on the 5 cells left in a number of ways. Most often batteries are never fully recharged during a passage and nothing changes. But you should keep a high voltage alarm on the max voltage for charging 5 cells instead of 6. If your max charging voltage is normally 14.4V then you should stop charging at 12V with 5 cells. Like others have posted, many chargers can be programmed to do that automatically.
If you are really venturing out into the unknown then you should... or could... have two series banks. If you take 2V AGM cells then Lifeline has great options in AGM: 6 times the 4CT-2V in series gives a 615Ah bank, 6x the 6CT-2V gives 900Ah and 6x the L16T-2V gives 1,200Ah. When you bring two of those, you can bring up to 2,400Ah house bank capacity. Other manufacturers go to much bigger cells even.
If you have two of those AGM banks, you don't need to have them parallel and you don't need a starter bank anymore. You can simply switch one to be the house bank and the ither the starter bank and then reverse that role periodically or when one bank is running out but more juice is needed. The only danger is not having enough for starting anymore which is why many carry 1 or 2 group31's like an Odyssey or Firefly for that. You can leave these AGM banks disconnected for long periods without damage as their self discharge is very low. Think a year without a problem.
If you go further yet, or don't want two banks then just bring a spare cell and use a DC-DC single cell charger to periodically recharge it. Lets say you do that every 6 months. When you loose a cell (I never hear that happen) then you simpky swap it for your spare cell.

For people who don't see the danger of parallel batteries: if one malfunctions, the others discharge into that one violently. I have had a flooded 12V battery explode because of that, this danger is real even when somebody cries that it's safe. Modern batteries have very high short circuit currents: my Odysseys do 5,000 amps EACH. Be wise, look at pro installations. For boats check out the 2V cell installations on boats like Contests, Oysters etc. If you use parallel then pkease fuse each string to make it safer.

[ramblinrod]

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.

Where did you come up with this?

If two identical batteries are in parallel, the internal impedance is equal. With no load, they sit at a steady state, and no current flows between them.

If one battery develops a shorted cell, it's internal impedance lowers, and current flows from the good battery, to the bad one, in an attempt to return to steady state.

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.

While FLA batteries store a lot of energy, and can give up a lot to a dead short (lets say 1000 A), to a parallel battery with a shorted cell, it will be much less. The lower the impedance of the shorted battery, the higher the current drawn, the more the good battery voltage sags near the voltage of the defective battery reducing the effect.

For Lion batteries, capable of delivering much higher instantaneous current, this could be an issue, and the reason why Lion batteries need sophisticated battery management systems.

To not parallel FLA batteries due to the risk of a shorted cell, is either a misunderstanding of the risk, or an irrational phobia. It is not going to cause any significant issues. 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.

[TeddyDiver]

Originally Posted by Pete7

Not in my experience. Presumably you are planning on having a DC/DC converter with a 12v output. Well my experience on a previous boat was that the electronics and fridge actually ran better on 24v or 27v when the alternator was running. The only item that couldn't run on 24v was the Icom VHF radio so that had a cheap 12v converter.

Pete

All galley appliances are 240v/50hz as other big draw stuff running from the inverter or generator. Baking, sauna, laundry, scuba compressor and things like that only when engine is running, every morning before the solar kicks in or when motoring etc.. Only nav gadgets and lights mostly 12v. No autopilot. never

BR Teddy

[TeddyDiver]

Originally Posted by ramblinrod

Where did you come up with this?

https://www.google.fi/webhp?gfe_rd=c...attery&spf=677

Though some of search result are deliberately detonated there are some scary stuff too

BR Teddy

[GrowleyMonster]

Originally Posted by ramblinrod

Actually, I believe you mean a boat having electric propulsion. ;-)

And yes, this changes the vessel storage and charging capacity needs dramatically.

Because this represents such a small percentage of boats on the water, it really does need to be considered in isolation.

This is a case where expensive DC - DC converters, monitoring, and charging equipment may be warranted (if one can justify electric propulsion to begin with).

Have you priced DC/DC converters lately? Or inverters? I don't mean top brands with advertising budgets either. They are getting pretty cheap. Knowing what I know now, if I had a diesel I would still go with a 48v bank or else jump up to 144v. 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. It is a thing, and it should be considered realistically. The benefits are obvious. A short battery can be dropped from the string, and everything still works. Higher voltage means lower current into the inverters and converters, so lower line losses and smaller wire. GFCI protected breakers of course become mandatory but no biggie. 220AH at 144v gets the same work done as 660AH at 48v or 2640AH at 12v, without parallel wiring and the risks involved. Not saying that this is for everybody. For some folks a pair of 12v batts isolated with a battery switch is all that is needed. One battery goes soft or dead, switch to the other one. Both weak and you need to start the diesel, switch to "BOTH". Simple and cheap. For those who just need to power nav lights and bilge pump and maybe a couple of LED lamps, perfect. But if you need 600lbs of batteries to get by, then some consideration should be given to a series arrangement. With the cost of the requisite electronics and their efficiency, it is a realistic alternative to a series/parallel arrangement with fuses and diodes and stuff.

[ramblinrod]

Originally Posted by s/v Jedi

I really hope that people reading this are starting to realize that series connection is the better option and have learned to mostly ignore the ramblin going on here.
If your bank is only 12V, which is the most vulnerable setup for a failure of a cell as you lose 1/6th of your voltage, then you can still continue in several ways: if only back to the marina, switch over to your starting bank. Boats that push further have bigger starting banks as well: I have two Odyssey group 31 beasts that are more powerful than many house banks. But if you are on an off-shore passage, you can live on the 5 cells left in a number of ways. Most often batteries are never fully recharged during a passage and nothing changes. But you should keep a high voltage alarm on the max voltage for charging 5 cells instead of 6. If your max charging voltage is normally 14.4V then you should stop charging at 12V with 5 cells. Like others have posted, many chargers can be programmed to do that automatically.
If you are really venturing out into the unknown then you should... or could... have two series banks. If you take 2V AGM cells then Lifeline has great options in AGM: 6 times the 4CT-2V in series gives a 615Ah bank, 6x the 6CT-2V gives 900Ah and 6x the L16T-2V gives 1,200Ah. When you bring two of those, you can bring up to 2,400Ah house bank capacity. Other manufacturers go to much bigger cells even.
If you have two of those AGM banks, you don't need to have them parallel and you don't need a starter bank anymore. You can simply switch one to be the house bank and the ither the starter bank and then reverse that role periodically or when one bank is running out but more juice is needed. The only danger is not having enough for starting anymore which is why many carry 1 or 2 group31's like an Odyssey or Firefly for that. You can leave these AGM banks disconnected for long periods without damage as their self discharge is very low. Think a year without a problem.
If you go further yet, or don't want two banks then just bring a spare cell and use a DC-DC single cell charger to periodically recharge it. Lets say you do that every 6 months. When you loose a cell (I never hear that happen) then you simpky swap it for your spare cell.

For people who don't see the danger of parallel batteries: if one malfunctions, the others discharge into that one violently. I have had a flooded 12V battery explode because of that, this danger is real even when somebody cries that it's safe. Modern batteries have very high short circuit currents: my Odysseys do 5,000 amps EACH. Be wise, look at pro installations. For boats check out the 2V cell installations on boats like Contests, Oysters etc. If you use parallel then pkease fuse each string to make it safer.

Again, millions and millions of boats on the water with FLA parallel bank pro installations that conform with ABYC and NFPA standards. No problems.

Yes, if one decides to apply more dangerous batteries to their boat, risks increase for all wiring configurations series and parallel.

6 x Grp 31s in parallel, provides for a very effective and safe 700 A-hr bank, with ample natural redundancy, without need of battery management systems (other than maybe an A/B switch usually on both). Risk of a meltdown if a cell shorts. Nil. Difficulty to replace a battery if needed. Nil.

This is quite adequate for a boat with a 175 A-hr per day average energy consumption (much higher than most cruising boats in the 30 to 50 ft range.

How far off-shore really makes little difference, except that if your batteries are near end of life before planning a distant passage, I don't care what technology they are, or what wiring configuration they are in, replace them all.

If they are exotic, it will be more difficult and expensive, so one may be tempted to push it instead of replace it, and get themselves into trouble.

I don't know about anyone else, but I know I would find it hard to take a large bank of exotic batteries worth $1000s and $1000s to replace, that are working fine, to the dump, because, hmmm, will they fail over the next year before I get somewhere where I can buy a replacement?

Compare this to the 6 x Grp 31s in parallel. Sail along, if a battery fails, jumper it out, and pick a replacement anywhere at your convenience.

I wonder how many circumnavigations have been completed successfully with 12 Vdc batteries in parallel. My guess is in the neighbourhood of 98%.

[ramblinrod]

Originally Posted by s/v Jedi

I really hope that people reading this are starting to realize that series connection is the better option and have learned to mostly ignore the ramblin going on here.
If your bank is only 12V, which is the most vulnerable setup for a failure of a cell as you lose 1/6th of your voltage, then you can still continue in several ways: if only back to the marina, switch over to your starting bank. Boats that push further have bigger starting banks as well: I have two Odyssey group 31 beasts that are more powerful than many house banks. But if you are on an off-shore passage, you can live on the 5 cells left in a number of ways. Most often batteries are never fully recharged during a passage and nothing changes. But you should keep a high voltage alarm on the max voltage for charging 5 cells instead of 6. If your max charging voltage is normally 14.4V then you should stop charging at 12V with 5 cells. Like others have posted, many chargers can be programmed to do that automatically.
If you are really venturing out into the unknown then you should... or could... have two series banks. If you take 2V AGM cells then Lifeline has great options in AGM: 6 times the 4CT-2V in series gives a 615Ah bank, 6x the 6CT-2V gives 900Ah and 6x the L16T-2V gives 1,200Ah. When you bring two of those, you can bring up to 2,400Ah house bank capacity. Other manufacturers go to much bigger cells even.
If you have two of those AGM banks, you don't need to have them parallel and you don't need a starter bank anymore. You can simply switch one to be the house bank and the ither the starter bank and then reverse that role periodically or when one bank is running out but more juice is needed. The only danger is not having enough for starting anymore which is why many carry 1 or 2 group31's like an Odyssey or Firefly for that. You can leave these AGM banks disconnected for long periods without damage as their self discharge is very low. Think a year without a problem.
If you go further yet, or don't want two banks then just bring a spare cell and use a DC-DC single cell charger to periodically recharge it. Lets say you do that every 6 months. When you loose a cell (I never hear that happen) then you simpky swap it for your spare cell.

For people who don't see the danger of parallel batteries: if one malfunctions, the others discharge into that one violently. I have had a flooded 12V battery explode because of that, this danger is real even when somebody cries that it's safe. Modern batteries have very high short circuit currents: my Odysseys do 5,000 amps EACH. Be wise, look at pro installations. For boats check out the 2V cell installations on boats like Contests, Oysters etc. If you use parallel then pkease fuse each string to make it safer.

Again, millions and millions of boats on the water with FLA parallel bank pro installations that conform with ABYC and NFPA standards. No problems.

Yes, if one decides to apply more dangerous batteries to their boat, risks increase for all wiring configurations series and parallel.

6 x Grp 31s in parallel, provides for a very effective and safe 700 A-hr bank, with ample natural redundancy, without need of battery management systems (other than maybe an A/B switch usually on both). Risk of a meltdown if a cell shorts. Nil. Difficulty to replace a battery if needed. Nil.

This is quite adequate for a boat with a 175 A-hr per day average energy consumption (much higher than most cruising boats in the 30 to 50 ft range.

How far off-shore really makes little difference, except that if your batteries are near end of life before planning a distant passage, I don't care what technology they are, or what wiring configuration they are in, replace them all.

If they are exotic, it will be more difficult and expensive, so one may be tempted to push it instead of replace it, and get themselves into trouble.

I don't know about anyone else, but I know I would find it hard to take a large bank of exotic batteries worth $1000s and $1000s to replace, that are working fine, to the dump, because, hmmm, will they fail over the next year before I get somewhere where I can buy a replacement?

Compare this to the 6 x Grp 31s in parallel. Sail along, if a battery fails, jumper it out, and pick a replacement anywhere at your convenience.

I wonder how many circumnavigations have been completed successfully with 12 Vdc batteries in parallel? My guess is in the neighbourhood of 98%.