House bank 6 volt vs 2 volt cells

[Capt Hugh Wilde]

Originally Posted by nimblemotors

Just use two of these 900ah batteries, only 1 jumper...
Trojan 897 Amp-hour 6 Volt Deep Cycle Battery
Surely you can manage 415lb, if you can install a diesel engine, you can install these..

Which batteries would be easier to replace when out cruising ?

If I had a battery locker big enough, that would be fine, but I am sure whoever had to replace them would cuss me.

[Tx J]

Originally Posted by s/v Jedi

You are misinformed. A 12V battery that is run down to 10V is a dead battery. But 5x fully charged 2V cells in series are a different matter, because they can supply the power. Also, it will be 5x 2.10V = 10.5V.

I have started my engine on that, run all my lights and navigation equipment on that.
(But, have they suffered damage that will not manifest itself for some time?)
There was one item that did not work and it was that crappy rn300 gps from Raytheon. It hardly works on 12V either so no surprise.

On construction: there is no comparison between a single cell and a battery with multiple internal cells. It is also silly to put that to discussion, just check any mission critical system and you see the single cells, for good reason. Diesel-electric submarines, emergency power for telcos, hospitals, the highest class yachts all have them too.

There is a qualification to this assertion above (bolded) though.
Yes, these critical applications generally use strings of 2V cells to create large UPS's, which supply all the using switch and transmission (motive) equipment loads directly [EG: Telco power plants (or subs) with nominal 48V & 24V (52.8V/26.4V actual, charged and maintained with very large multiple rectifier banks fed with commercial ('shore') or genset (diesel propulsion plant) AC].

But, the operative word is "strings". Beyond a certain wire/wireless center customer base size (and all D-E subs), more than one "string" of 2V cells will be provisioned, EG: String -48V-A, String -48V-B, String +24V-D, String -36V-E, etc., etc.

Normally, all strings will feed the main systems DC equipment ('house') loads (AC loads run off commercial ('shore') power or a genset/inverters, but the core essential systems can run/limp without any AC power).
But, if one battery string develops a problem (say a bad 2V cell...) that string will be isolated until battery repairs are effected, while the other string(s) continue to feed the system loads. Not very practical on most pleasure craft.
A crippled 2V/cell battery string is never allowed to continue online. If mains AC sourcing is totally lost though, the system runs solely on the batteries until a low voltage cutoff point is reached of course (in extremis only, see next paragraph)).
In the absence of commercial AC, massive gensets (diesel or turbine) will kick on; if the genset fails or runs out of diesel fuel, the center will run off the battery strings until an exhaust point is reached. Then it's lights out, and even those massive 2V cells can reverse polarity if pulled too low, venga kaput.

BTW, I'm getting as old as sand, so I even remember the huge old open-top tank cells housed in giant white ceramic tiled rooms/compartments (walls, floors, everything tiled (like a gigantic bathroom/shower/restroom, talk about 'echoes'; and the last guy to walk in one with a smoke was vaporized, heh ).

The reason 2V cells are used in such applications are of course: the previously mentioned simplicity, economic costs, reliability; and even tradition, since these usages go back to the beginning of practical 'lectricity apps.

I'd still go with the 6V cells for some of the previous reasons mentioned by others (like, you're not going to find a usable 2V cell in Timbuktwo).

[pbiJim]

Originally Posted by s/v Jedi

When you buy a 12 V battery, you buy it of the capacity you need, i.e. 100Ah. Nobody buys 4 batteries of 25Ah instead and connects these in parallel.

I have seen several installations where people have done just that, hook several 12v batteries in parallel. I'm not going to claim that it is the best way to go, but it is done by some people. The example that you give of 25ah batteries may be a bit out of the box though.

[Tx J]

Quote:
Originally Posted by s/v Jedi
When you buy a 12 V battery, you buy it of the capacity you need, i.e. 100Ah. Nobody buys 4 batteries of 25Ah instead and connects these in parallel.

Originally Posted by pbiJim

I have seen several installations where people have done just that, hook several 12v batteries in parallel. I'm not going to claim that it is the best way to go, but it is done by some people. The example that you give of 25ah batteries may be a bit out of the box though.

??
You're both simply describing the dreaded "house bank", wherein your average mullet parallels two or more 12V batteries of 90Ah or 130Ah or whatever combination is handy (or builds it with series 6V, and possibly parallels too) to make up a primary vessel DC power source/bank of some large Ah capacity to run the house loads for a day or four.
Small scale=bad, larger scale=gooder?
Who marks the scale? Answer- the size and needs of the particular boat owner.

[ka4wja]

Hugh,
You've gotten some good input and advice already (MaineSail and Jedi are great voices of knowledge), perhaps I can add some more and give some real-world experience / advice, as I have 2-volt cells making up my house bank.

1) In general "2-volt cells" have much thicker positive plates....allowing for deeper-cycling and much higher number of "cycles", than most other types of batteries used for house battery banks on-board, such as golf-cart batteries (and significantly better than what are typically sold as "deep-cycle" batteries!!!)
There is more to a house battery bank than its A/H capacity!!
Its ability to deep-cycle and its number-of-cycles in its lifetime, are just as important!!!

There was some discussion about this here...(have a look at post #26 here.)
http://www.cruisersforum.com/forums/...s-62379-2.html





2) Here, I'd like to qualify Nick's comment....

Originally Posted by s/v Jedi

But when it comes to bigger capacities, people suddenly start connecting things in parallel well before it is needed. I can only come up with two reasons and that is to get things cheaper and ignorance.

There actually is a THIRD reason to do this....
And, that is the size/shape of the space on-board for the batteries may need to be taken into consideration when choosing battery cells..
I do not have the room on my current boat for the very tall cells, but I did have room horizontally to install more cells....
So, on my current boat, I use 375 A/H 2-volt cells....in three strings of six cells in a string...
(Sorry Nick, but we all don't sail a Dashew-designed Sundeer, where tall/deep battery cells for your house battery bank was specifically part of the vessel's design.... Some of us need to make do with the space we have on-board!!!)







3) I currently have EIGHTEEN (yes, 18) Rolls "2-volt" deep-cycle cells, at 375 A/H each, as my house bank. (and I love 'em!!)
{see my article about them, along with the hi-res pictures of them, in the link..}
Battery

These are arranged in three strings of six-cells each, and the three strings in parallel, giving me a 12vdc house bank with 1125 A/H capacity....
(see pictures)
And, each cell only weighs 36 lbs!!!

I previously have had 12-volt 8D deep-cycle batteries (Rolls "Big Red" 8D's) as a house bank on-board before...(see one of them, somewhat, in this picture here... 4706107 )

And, in years past on a previous boat, I had 6-volt deep-cycle batteries (Rolls L-16's) in series/parallel...


I took these pictures before installing the hold-down bars, and before cleaning-up the wiring runs....but you get the point....










4) Next, I agree mostly with Nick (s/v Jedi), that there is a big difference between 10.5 volts out of a 10.5 volt battery (FIVE 2.1 volt cells), vs. 10.5 volts out of a 12.6 volt battery (a DEAD six-cell, 12.6 volt battery)!
And yes, five good cells (bypassing a bad cell) will most probably start almost any sailboat diesel and will run many electronics, and certainly will still run Nav Lights, pumps, etc....

But, amytom does have a point...
If you do loose a cell, you will need to replace it....so WHERE you are sailing, and how soon / how far away you are from a source of these 2-volt cells IS something to consider!!
You can certainly "get to port" with just 5 good cells, but I'd not recommend trying a circumnavigation with only 5 cells...

Further, the weight of the cells and your ability to install/move/replace them should also be a consideration....
(my cells weigh just 36 lbs each...and they are 375 A/H's...)





5) So, all the above in mind, you may wish to consider using two strings of six "2-volt cells", thereby giving you"
a) most of the "electrical and longevity advantage" of 2-volt cells..
b) the "reasonable size/weight advantage" of 2-volt cells...
c) should you have a VERY rare cell failure, you'd retain the ability to run one full six cell string as a "full-voltage battery" for voltage sensitive equipment, AND still have the full-current available from the other 5-cells, should you need it....


I do hope this helps some...
Fair winds...


John
s/v Annie Laurie

[Maine Sail]

Originally Posted by ka4wja

1) In general "2-volt cells" have much thicker positive plates....allowing for deeper-cycling and much higher number of "cycles", than most other types of batteries used for house battery banks on-board, such as golf-cart batteries (and significantly better than what are typically sold as "deep-cycle" batteries!!!)
There is more to a house battery bank than its A/H capacity!!
Its ability to deep-cycle and its number-of-cycles in its lifetime, are just as important!!!




John
s/v Annie Laurie

John,

Excellent input except for the above statement, but only as it relates to the Lifelines the OP wants.

Lifeline rates their 2V cells at the same cycle life as their 6V and their 12V batteries. This is different from most FLA batteries. If going 2V then Rolls are an excellent choice!!! Nice set up BTW...

[ka4wja]

Maine,
Opps, I didn't know that about the Lifeline's...
Thanks for that piece of info!!
(And, a second opps, as I forgot that Hugh was looking at Lifeline's.)


Fair winds.

John
s/v Annie Laurie

[ka4wja]

Hugh,
FYI, the Rolls "2-volt cell" batteries I'm using are the 12EHG-375PM's (which fit the battery boxes / battery are, on my boat)...
http://rollsbattery.com/public/specsheets/12EHG375P.pdf

And, I bought them a few years ago from David at East Coast Battery, in Ft. Lauderdale, FL....a great guy, and a great family owned/operated business...
(I've been buying batteries from them for years, and my parents were customers of David's dad, for many years, starting in the 1960's..)
index


Fair winds...

John
s/v Annie Laurie

[FlyingCloud1937]

Thought I would chime in here, Haven't posted for a while, been at sea for the last 6 weeks.

Thicker plates means longer life, I agree.
But, it also means higher internal resistance, which then brings Pukert into the equation.

All this means is we need to size battery banks, to the load expected, and balance that with the charge regime available.

If we have a use that requires high amp loads (such as an inverter load) then the higher resistance to amp/hr size...may not be the best battery bank.

Unless we can size the bank to Pukert, in absence to the required size/weight of a long term bank, then we need consider discharge availibility.

On land, when we size for load, and longevity, we need not size on the watts out to weight factor.

But on a floating home(boat, at least part time home), we must consider it.

Lloyd

[SV Maclas]

I would personally stick with the simple solution. 6V batteries can be found everywhere.

[GordMay]

Originally Posted by FlyingCloud1937

... Thicker plates means longer life, I agree.
But, it also means higher internal resistance, which then brings Pukert into the equation ...

I would have thought thicker plates would present less internal resistance (than thinner plates).
Please explain.

[nes]

While this discussion is about the use of either 2 VDC cells or 6 VDC batteries, to achieve 900 AH of battery capacity, I would suggest that another point that needs to be looked at (if the 6 VDC arrangement is chosen), is the method of wiring. In the case of the 2 VDC cell string the wiring is simple and obvious, but in the case of series/parallel for the 6 VDC, the wiring is an important part of what you are looking for. I ran across this link late last year, (probably on one of the threads here) and I believe you should review this, in your discussion on the 6 VDC battery option.

SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank

In my case, I only had room in my battery compartment for 3 batteries, and to get there, I had to move the charger to another compartment. I chose to use a 12 VDC 95 AH for the backup starter battery, and a pair of 240 AH 6 VDC batteries wired in series for the house bank. Short of redesigning the interior of my boat, I was limited in what would fit. The original design was to have either 1 110 AH 12 VDC battery or 2 110 AH 12 VDC batteries, for a maximum of 220 AH, with my configuration, I have 335 AH.

[ka4wja]

Lloyd,
I assume that Hugh (the original poster) has taken into consideration all the use/load requirements and the recharge capabilities of the system, as he mentioned many of the specifics...

Originally Posted by FlyingCloud1937

All this means is we need to size battery banks, to the load expected, and balance that with the charge regime available.

But, for others reading this thread this is good advice!!





Now back to the specifics.....
While thicker-plates batteries do generally have higher internal resistances, these true deep-cycle lead-antimony plate batteries can surprisingly handle quite significant loads...
And, I can't imagine many of us on our fairly small boats having a problem with discharge capacities, and since most (including Hugh, the OP) have decent solar arrays that can provide a long steady acceptable current recharge rate, I'm not sure the internal resistance differences would make any difference...


As an example my Rolls 2-volt cell bank (1125 A/H @20-hr rate) is spec'd at 4590 CCA's (5750 MCA's), and spec'd to deliver 95 amps for 10 hours straight and 150 amps continuous for 6 hours straight....
(Note, that nobody would actually do this as this is a significant discharge that would not only reduce the life of the cells, but take one heck of a long time to re-charge!!
This is only for example!!)
And, in addition to my solar array (which can provide as much 40 amps cont and > 200 A/H per day) I have a towed water-gen, a 120-amp alt. and 90-amp charger (run from either shore power or 6kw genset)


I don't have a big inverter....just a small portable 300 w unit, for very occasional use....
But curious just how big of an inverter and for how long do some of you run it, that this would an issue???

{I suspect the highest current use on-board would be bow thrusters (and engine starter motors), and these are very short-lived....so the CCA ratings might be of more importance for these applications...}



Fair winds..

John
s/v Annie Laurie

[ka4wja]

As long as the batteries are wired correctly, in the real world, I'm not sure the "number of cables" is too much of an issue...
I'll defer to MaineSail on this one...

But if considering a "2-volt cell" approach, FYI, many (most?) 2-volt cells have a "bolt-together" facility that allows for series connection of cells WITHOUT cables....making the issue sort of moot...
(see photos of my battery bank in post above, as an example)


Fair winds...

John
s/v Annie Laurie

[foggysail]

Originally Posted by boatpoker

I had 6v's for years, they took tremendous abuse, lasted a long time, are cheap, easy to install/remove and you can buy them anywhere.

My current boat came with two banks of 2v Rolls Surette's. One bank lasted only 3yrs of very light use, they came with hydro-caps that I'm now convinced are just marketng BS, are extremely difficult to remove as they lock together (and you can't just replace one bad cell) and are hideously expensive.

I once purchased 12 vdc Surettes for my sailboat. WHAT A MISTAKE!!! TALK ABOUT MARKETING HYPE---- there is sooooo much of it they actually get people to swear the batteries are worth the ransom demanded at time of purchase.