6v bank vs 12v bank

[john61ct]

Yes, that is why I said the generalization was over-generalized.

Once your search is within the **actual high quality** makers' lines only. then valid exceptions emerge.

But for noobs starting with the total universe of batteries **claimed** to be suitable, then the general guideline is very useful.

Also again AGMs are lots more expensive, per Ah per year, so if value for money is a priority, I only reco using them where sealed is actually needed.

A location that requires installing sideways, or where topping up water is difficult is of course such a case, for some.

[ranger58sb]

Value for money analysis can include time as a factor. My time is often more valuable than a buck or two here or there...

-Chris

[mitiempo]

Originally Posted by CaptMDG

What are the pros and cons of having either 1) two six volt batteries in series producing 450 AH, or 2) two twelve volt batteries (225 AH each) in parallel producing 450 AH. I am interested in the practical physics of these configurations. On paper they are the same, or are they?


I am not interested in costs, sizes, or weights of each bank, just in the practicality of each.

Based on those numbers you are comparing 2 L-16 6 volt batteries - almost 17" high and 120 lbs each to 8-D 12 volt batteries - nowhere as tall but over 20" long and about the same weight.

If you have room for either of the above why not use 4 Trojan T-105 or similar golf cart batteries in a series/parallel configuration for similar amp hour capacity in a much easier to handle size?

[Oceansailor]

Originally Posted by ranger42c

Have you seen a longevity comparison between Lifeline's GPL-4CT 6V AGM and their GPL-31XT 12V AGMs? (Or a similar comparison between 6V FLAs and deep cycle -- i.e., not dual-purpose -- 12Vs? (Rolls, I guess?)). The info on Lifeline's website suggests an equal number of lifetime cycles...



For me, "value" includes not having to yutz around trying to get access to service our AGMs, and reduced off-gassing... so its not a strict $$$ evaluation.



-Chris

I doubt that GPL-4CT and GPL31XT have the same cycle life? I read an article where they opened up a Lifeline 6V and compared to a 12V. The plates on the 6V was much thicker. I want to remember it was on MainSails web page? I might be wrong on that one.

[mikeo16]

I think available space needs to be an important factor along with intended use. Someone who is a a fulltime livaboard will have different needs than someone who takes a few multi week trips a year. If someone has the available space for 4 6-volt batteries wired in series (along with a reserve battery) parallel will benefit the most. For someone who does not have that much space, it is a tougher decision as 2 6-volts versus 1 12-volt the advantages are not as clear. The 6-volt batteries will likely have more cycles than normal 12-volt flooded batteries but higher end 12-volt batteries may be the same. In the end it boils down to intended use and how much you want to spend and not waste your money on something you don't really need.

[john61ct]

Originally Posted by Oceansailor

I doubt that GPL-4CT and GPL31XT have the same cycle life? I read an article where they opened up a Lifeline 6V and compared to a 12V. The plates on the 6V was much thicker.

Sounds right, easy to verify, call when support is open, might even get Dave Godber himself

[EmeraldCoastSailor]

Originally Posted by mitiempo

Based on those numbers you are comparing 2 L-16 6 volt batteries - almost 17" high and 120 lbs each to 8-D 12 volt batteries - nowhere as tall but over 20" long and about the same weight.

If you have room for either of the above why not use 4 Trojan T-105 or similar golf cart batteries in a series/parallel configuration for similar amp hour capacity in a much easier to handle size?

Interesting how you seem to be the only other person to notice the OP indicated a desire for a 450AH bank. If 450AH is the goal then 4 6v GC batts compare well IMHO to 2 8-D 12v batts.

[john61ct]

I assumed it was just an example, more a learning question on the science of the comparison.

500, 550 even 600 close enough.

Also OP did not clarify if they were aware of the 50% DoD guideline.

[alansmith]

John61, thanks for the link to Mainemarine article on deep cycle. I read that several years ago... and had forgotten about it. Great tutorial fellas if u want to brush up on it again. I have 2 cheap arse 12 v 100 amp/ hr that are Fla. one is a year old and the other has an unknown age. My boat is in Mexico. Hotter than Haiti in the summer in a closed cabin. I keep em topped with a 50 watt panel.

I am conflicted. I yearn for a Lifepo4 setup. I want about 400 amp/hr and want to keep the boat as light as possible since she is a trimaran. Looking at around 1200-1500 dollars from a company in China. My current bank weighs about 150 lbs I guess. It would require a bunch of other stuff with it. I can buy 4 gc 6 volt 230 amp/ hr batteries and wire them in series and parallel to get a 12 v 400+ amp/ he system for less than 500 dollars and not much else. Total weight would go up to 250 lbs. gulp! How to argue with that logic?

By the way... not trying to hijack ... but how do fellas deal with leaving boat unattended in hot cabins with lifepo4 banks for months at a time? Freaks me out. Educate me please.

[ranger58sb]

Originally Posted by Oceansailor

I doubt that GPL-4CT and GPL31XT have the same cycle life? I read an article where they opened up a Lifeline 6V and compared to a 12V. The plates on the 6V was much thicker. I want to remember it was on MainSails web page? I might be wrong on that one.

If you look at Lifeline's technical manual, the Expected Life Cycles chart (page 40 in Rev E of the doc) suggests 1000 cycles to 50% DoD for their deep cycle batteries -- without regard to battery voltages.

I'd suspect plates on their G31 12V GPL-3100T starter battery would be different from plates in their GPL-31XT... given that life cycle chart.

But I don't remember seeing a third party comparison of their 6V and 12V deep cycle batteries...

-Chris

[john61ct]

Originally Posted by alansmith

I have 2 cheap arse 12 v 100 amp/ hr
..
I yearn for a Lifepo4 setup. I want about 400 amp/hr

They'd weigh about the same.

> leaving boat unattended in hot cabins with lifepo4 banks for months at a time?

Cooler storage is better, but not worth running aircon, may die 10% earlier, but if that's off 20 years. . .

Or make it portable, keep in a cooled location.

[CaptTom]

Anchors suddenly seem so non-controversial. Even religion and politics don't seem to raise this level of controversy.

It does help to know all the pros and cons. I know which issues were important to me, and which didn't apply. I'm satisfied with the decision I made (not telling!)

I recommend the OP do the same.

You can spend your life trying to perfect your battery installation, monitoring and maintenance. You can learn the finer details of the chemistry and physics of batteries.

Or you can install what you think will work best for you, take reasonable care of them, and go cruising.

[ramblinrod]

Originally Posted by S/V Illusion

If the intent is to provide true redundancy maintaining sufficient capacity, it makes no sense to rely on one 12 v battery. Better advice would be two separate 6 v banks which can also be combined.

I think you missed the point,

I was referring to the comparison of 2 x 12 Vdc, 110 Ah batteries in parallel vs 2 x 6 Vdc 220 Ah batteries in series.

Both options will provide a 12 Vdc 220 Ah bank.

If one of two 6 Vdc batteries fail, the bank is useless because the remaining battery is only 6 Vdc.

If one of two 12 Vdc batteries fail, it can be isolated, and the remaining 12 Vdc battery used until one or both are replaced.

Most boats will have a provision to power house loads with the start battery in an emergency, but this of course has its own pitfalls.

[ramblinrod]

Originally Posted by john61ct

They'd weigh about the same.

> leaving boat unattended in hot cabins with lifepo4 banks for months at a time?

Cooler storage is better, but not worth running aircon, may die 10% earlier, but if that's off 20 years. . .

Or make it portable, keep in a cooled location.

20 years?

Geez us we only need to talk about LFP in a few more threads and I got 20, 20, who will give me 25, 25, 25 from EVM1023 who will give me 30 30, 30 from JohnCT62, 40 40, 40 from Exilation, 50, 50, 50 has been bid by Oldhaul.

Guys, this is getting ridiculous. The life expectancy of all batteries is dependant in the application and real charge cycles they are exposed to.

A relatively inexpensive FLA bank that is typically discharged to 75% +/- 10% and recharged to 100% with solar can easily last 5 years.

An LFP bank discharged to 0% (true) can be killed in 5 hours.

[john61ct]

Originally Posted by ramblinrod

A relatively inexpensive FLA bank that is typically discharged to 75% +/- 10% and recharged to 100% with solar can easily last 5 years.

Very low expectation, especially if both numbers are SoC there, even a Wally world special can do that