2x6V or 1x12V -- Trojan T-105's ??

[Bob Pullen HC-33 1981]

We have 6 Trojan T-105's, 6-Volt batteries in our house bank.
They are hooked up as 3x12V, for approx. 600 AH at 12Volts.
they are new, but the folks who were looking after the boat for a few months let a few of them dry up and kept charging...
end result = a couple of them drop their voltage substantially in a short time after being charged, and I am considering replacing 2 of them
Here's the question: I was considering the benefits v.s. disadvantages of replacing 2 of them with 1 of the T-105 12V. Is is true the 6V model will have a slower discharge or keep it's charge longer than a 12V (under identical conditions)?
Anyone?
many thanks, as always
Bob
s/v Seanorita
Hunter 33 Cherubini
Isla Mujeres, Mexico

 

[Stu Jackson]

No.

And this answers your other question. see http://forums.catalina.sailboatowners.com/showthread.php?t=115770

 

[nateman]

My limited understanding after reading about this, is that the 6volt's have thicker plates than there 12volt counter parts. Running two 6volt batteries in series to achieve 12volts is a better option to a single 12volt battery.

 

[Maine Sail]

Bob,

Ideally you should not even mix batteries of differing ages let alone brands, type, voltages or group size. If those batts were wired as one bank, at a minimum you'd be wise to replace them with T-105's. A 12v battery will have different plate thicknesses than a T-105 and will chrarge and discharge slightly differently.

The perfect situation, for longevity, would be to replace the entire bank at the same time with inventory stock out of the same date batch. Mixing old and new, especially with batteries that have been abused and boiled off, may result in a short life of the two new ones.

It's your boat so you should do what ever makes you comfortable. Mixing old and new does not make me comfortable and mixing brands, voltages and group types definitely would not make me comfortable.

What was type/brand of charger and why was it left on for so long? Did it have a float mode?

 

[Bob Pullen HC-33 1981]

Many thanks for the kindness of your replies.
I appreciate your advice, and yes, it makes total sense.
The batt's were cooked due to a "failure to communicate..." and not much else
Unfortunately, I will have to mix the ages, and will replace them with 2x6V.
thanks again
Bob

 

[sailingdog]

AFAIK, Trojan does not make a T105 12 VDC battery. They do make 12 VDC batteries, but not one called a T105.

As Maine Sail has pointed out, you'd really be best off replacing all of the batteries...next best would be replacing the two dead ones with two new T-105s.

 

[Bob Pullen HC-33 1981]

sorry to have crossed the picky line...
don't know the name/# of the battery, but it is the size of the T-105, color, etc... and was quoted to me by the trojan dealer here in mexico, as a 12V T-105
...will make sure to let them know they need to do better.
thanks again
Bob

 

[Stu Jackson]

Bob, go to Trojan's website

They have some very good information. If you Google Trojan, you may come up with some other funny websites, but I'm sure you'll learn the differences!

 

[Bob Pullen HC-33 1981]

thanks Stu
looks like I will have to bite the proverbial bullet and spring for 2 replacements
at around $135 ea., not a fun dent in the budget
will probably also try the equalizing process, if I can get a good description of the steps and the type of charger needed
hope I can find one around here
thanks again for the help to one and all
Bob

 

[Stu Jackson]

thanks Stu
looks like I will have to bite the proverbial bullet and spring for 2 replacements
at around $135 ea., not a fun dent in the budget
will probably also try the equalizing process, if I can get a good description of the steps and the type of charger needed
hope I can find one around here
Bob

That's a pretty good price. I've heard of Sam's Clubs at $79 each, but it all depends on where you are and what you can get.

Equalizing: see WM Advisor, here: http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/Battery-Charging.htm

You need a shorepower charger that has that feature. Here's our expert battery charger evaluation: http://c34.org/bbs/index.php/topic,4352.0.html

What charger do you have? Some alternator regulators (like my Balmar M612) have an equalization setting in their programs, but you have to run the engine at cruising speed for at least four hours. If you're goin' somewhere anyway, not an issue. I did it once, but it's much easier when tied into shorepower.

Also download and read the Ample Power Primer, www.amplepower.com, tech docts tab. You have to break in your new batteries, really! :naughty: A good read for everyone. It explains charging and equalization, too.

 

[Bob Pullen HC-33 1981]

Thanks Stu! That's exactly what I need...to understand the subject matter a bunch better!! Will read up and give it a try. Unfortunately, don't have a hydrometer available, and will have to look around as to what type of shore based charger I can find. Not sure I'll fiind one with an equalizing setting, if such a thing exists, so I'll definitely have to understand the process much better b4 starting.
The 30A charger that runs off shore power & alternator is encased way behind the engine, and doesn't seem to have any switches, settings, etc...just a meter. According to the prev.owner it will put out 10A on each of 3 legs (not sure what that means at this point), but my Trimetric 2020 shows it charging, often starting out at 20+A, then levelling off to smaller quantities as the batts get fiilled up.
Not sure what I want to be looking for in the charger that will suit my equalization needs, but I will read up then give it my best shot, and hope for an improvement.
thanks again for your help and assistance
very kind
Bob

 

[druid]

Having analyzed the situation to death, I see no valid reason not to mix battery "ages". There are some reasons for not mixing types, but it's not critical - I had a 4D and a Group 27, replaced by 2x6V and two Group 27's, on my Cat 36 and had no problems once I chucked the CanTy charger and put in a Xantrex.

There's no difference electrically between 2x6V and 1x12V if they're otherwise identical (same size plates, etc), since the 6V is really 3x2V and the 12V is really 6x2V. The advantage of the 2x6V is that a 6V battery is manageable, weight-wise. Ever tried lifting an 8D battery?

druid

 

[Maine Sail]

There's no difference electrically between 2x6V and 1x12V if they're otherwise identical (same size plates, etc), since the 6V is really 3x2V and the 12V is really 6x2V.

Technically there is no difference if you are talking cell voltage of 2.1V but there is still a difference because they are not "identical".

Unfortunately cell chemistry is just not as simple as saying all cells should be at 2.1 volts whether in a 6V battery or a 12V. What that fails to acknowledge is the capacity of each cell, how fast or slow if delivers the stored energy and how fast or slow it can accepts a charge. Thick plate batteries are slower to charge and slower to deliver stored energy. Thin plate batteries the opposite.

Even 6V GC2 sizes from different manufacturers are slightly different and will accept current and discharge current slightly differently. This is not a problem if the batts are in separate banks, but when combined into one bank it can result in a shorter over all cycle life.

The reason 6V batteries can take so much abuse is the thickness of the internal plates when compared to a deep cycle 12V battery. Thicker plates take longer to charge than do thinner plates. Mixing a thin plate battery with a thick plate battery may chronically undercharge the thick plate battery or over charge the 12v depending upon where the alternator V sense is placed.

They need to fit six sets of plates in a group 27 (thin plates) and only three sets in a 6V GC2 (thick plates). Because of this the batteries behave slightly differently under both discharge and charging.

Not mixing old and new is still good practice for overall cycle life of the bank and return on investment. Will it work, can you mix them in the same bank? Sure, but you can shorten the life of the new batts by doing so.


You don't need to take our word for it though Nigel Calder describes this quite nicely:


Quote Nigel Calder:

"What is important, however, in both series and parallel connections, is not to connect different types of batteries (eg., wet-cells and gel-cells; cranking and deep-cycle) or batteries of different ages or capacities - differences between the batteries will accelerate the destruction of both."

 

[GuyT]

I developed a battery management system for low voltage DC battery systems because of the problems batteries have maintaining equal charge in low voltage strings.
Using 2 batteries in series does have state of charge issues that generally two batteries in parallel do not. But... wet batteries that are frequently equalized or force above float will eliminate the state of charge issues and force a equal charge across them.
I like parallel ing batteries personally because you could easily put an old one in parallel with a new one. You could also use a 100 ah and a 120 ah in parallel and have no issues.
Paralleling too many batteries can be problematic but many manufacturers recommend no more than 6. Good luck with your decision.