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12-24-2009, 12:33 PM
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#15
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Senior Member
Join Date: May 2007
Posts: 632
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re: "a six volt battery will weigh approximately as much as a twelve volt battery. That means that each cell in a six volt battery is about twice as massive (lead) as a twelve volt battery cell" -- if you look at the spec sheets, you'll find that all lead acid batteries of the type normally used in RV's run at about 20 to 25 watt hours per pound of battery. Theory papers will often refer to 45 to 50 watt hours per kg.
The 'pounds of lead' can lead to an interesting consideration of the teaching myths often used for lead acid batteries and the physical chemistry considerations for reaction exposure and current rates. Lead inside a solid chunk isn't available for chemical reaction so a battery must have its lead near the surface. Current depends upon the surface to volume ratio of reactants. That's why batteries are built the way they are rather than the way they are often depicted.
Again, the data I have seen for battery life makes it very clear that it is use and maintenance that are the primary factors in longevity. Whether it is the Az Wind Sun FAQ expected life table, cycles per depth of discharge graphs, the cost benefit analysis behind the 50% SoC rule, the data about causes of battery failure, or the conditions in warranties, the only factors that are consistently prominent above the noise involve use and maintenance.
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12-24-2009, 09:31 PM
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#16
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Member
Monaco Owners Club
Join Date: Nov 2007
Posts: 39
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Hi Guys,
Great information, thanks. We seldom dry camp and when at home the MH is always pluged in. The converter seems to always be on "flot charging". Is that normal? I check the batteries once a month and add only distilled water. i am not sure how old they realy are. Bought the MH new in April 07. I think I will be going to Sears, Sams or Advance Auto.
__________________
2007 HR Endeavor
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12-24-2009, 10:06 PM
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#17
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Registered User
Join Date: Aug 2009
Posts: 256
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Have you ever done an Equalization charge on them?? Might want to try it once to see if it helps. I do it one to two times per year.
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12-25-2009, 08:24 AM
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#18
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Senior Member
Join Date: May 2007
Posts: 632
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re: "The converter seems to always be on "flot charging". Is that normal?" -- when the battery is fully charged, float charging is normally applied for battery maintenance. That is a voltage of about 13.5 volts plus or minus depending upon temperature. The problems of getting just the right float voltage plus that of stratification of electrolyte from just sitting plus a slow sulfation are better solved by a maintenance charging device that does more than just apply a float charge. Look at what the ChargeWizard or WFCO converters do or the technique used by the BatteryMinder(tm) as examples of modern methods for battery storage maintenance.
An equalization charge is not normally needed for RV batteries that are in intermittent use and properly charged and maintained between uses. Equalization is an intentional battery over charge intended to make sure that all cells are fully (equally) charged and it is only needed if routine battery charging has been weak and marginal (e.g. many solar systems).
If you need to add water to the battery electrolyte every month, your batteries are being overcharged. That is a typical situation with many RV converters on float with a float voltage set a tad too high. Many batteries have suffered a premature death from that cause.
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12-25-2009, 11:24 AM
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#19
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Senior Member
Damon Owners Club Workhorse Chassis Owner
Join Date: Mar 2009
Posts: 24,024
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In another forum there is a very detailed discussion of the differences between Deep Cycle and Starting batteires.
There are chemical differences as well as differences in the construction.. One type has a lot of thin plates. the other has fewer thicker plates, for example.
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Home is where I park it!
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12-25-2009, 12:02 PM
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#20
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Senior Member
Join Date: May 2007
Posts: 632
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re "In another forum there is a very detailed discussion of the differences between Deep Cycle and Starting batteires." -- link, please.
I have seen so many of these, and have seen people trying to use many inane esoterica from them to try to resolve their cognitive dissonance but I have yet to see one that can actually define "deep cycle battery" in objective and measurable terms, especially in the context of those batteries commonly used for RV service. (all lead acid batteries suffer significant loss of life when cycled to what are considered deep levels)
Yes, there are differences in chemistry and battery construction and batteries are manufactured with a focus on differing application. These differences are matters of degree in the cost vs quality vs capacity tradeoffs in lead acid battery manufacturing. There are no distinctive boundaries such as between deep-cycle vs starting. Yes there are doping differences such as in calcium vs antimony as a balance between plate strength and charge gassing (sealed vs open cell). Anyone who looks at spec sheets and warranties can see this.
But when you look at the variances in battery measures (spec sheets) and compare them to the known 10% or more variances due to such things as temperature, current draw, aging, and even cycle to cycle variances, you'll find that a lot of the arguments about which batteries are better are about things that don't make much difference for RV use.
This thread is so typical: I ask for solid data, measurement, definition, and specification and the response supplies no such objective material, just repeated assertion. Thank goodness it hasn't gone more desperate than that as it sometimes does.
For some of the resources I use for my assertions and conclusions, see Understanding batteries, start with these links.
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12-26-2009, 09:48 AM
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#21
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Senior Member
Damon Owners Club Workhorse Chassis Owner
Join Date: Mar 2009
Posts: 24,024
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Well.. I will say that I have read some of those many threads you mentioned and DO understand the differences. I also understnad the logic behind the differences.
In my opinion (And based upon observation) there are other important differnces between a six volt golf car battery and a 12 volt starting battery as well.. These have nothing to do with the plates or the chemistery but with the case design..
The six volt batteries I have seem to have more head and foot room than the 12 volts I've seen.
What does this mean?
Well. on a flooded wet cell it is important to keep the plates under electrolyte (Liquid) if they get dry.. they don't really like that much. More head room means that you can go longer between waterings.. This may or may not be important depending on how often YOU check your battery.. But in the golf car world.. Figure the person checking them is not the owner so .. A bit of laxness is expected.
More foot room.. Sometimes metallic particals will "Flake off" the plates.. When the level of this debris reaches the plates.. NEW BATTERY TIME.. More foot room means.. More time between NEW BATTERY TIME happenings.
Now, this has nothing to do with battery performance or anything else save.. Lifespan.
ANd finally the biggie.
Most 12 volt designs are made in "Runs" and today, for example, we are going to run Group 27 maintence free.. Next week we will re-tool and run Group 29's and last week we ran Group 31's
However with hundreds of golf courses in each state, and each golf course has, perhaps dozens of golf cars. and each car takes six batteries... The six volt golf car line is not shut down and re-tooled at great expense every so often, it runs constant.
This means.. Lower per-unit cost.
__________________
Home is where I park it!
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12-26-2009, 10:48 AM
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#22
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Senior Member
Join Date: May 2007
Posts: 632
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again ... and again: the numbers don't match impressions.
headroom, footroom, or whatever, longevity statistics for batteries typically used for RV service do not show any longevity improvements with a correlation to battery voltage. See the Az Wind Sun FAQ chart, as an example. Check the warranties on batteries as another.
Matters of battery design, such as described have little to nothing to do with battery voltage and very much to do with the intended purpose of the battery and you can find such variances in design at all common battery voltages. (I mean, just look at a manufacturer's line card to see)
I do really think measures are much better for a guide than perceptions and desires.
The idea that an RV is a golf cart and that the two can be compared is another distraction. Golf cart batteries suffer 'industrial' service where they are run down daily and recharged nightly. Their life expectancy is in line with their warranties and cycle rates and depths. RV batteries have an entirely different usage profile and, if properly maintained can be expected to last much longer.
The manufacturing runs argument is a new one for me. congrats on that! But I do think you need to realize that often the only difference is the number of structures of the same type and design that are installed.
IMHO it is a plague in these discussions to have so much of what some people want to be and so little of what actually is.
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12-27-2009, 02:26 PM
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#23
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Senior Member
Damon Owners Club Workhorse Chassis Owner
Join Date: Mar 2009
Posts: 24,024
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Quote:
The idea that an RV is a golf cart and that the two can be compared is another distraction. Golf cart batteries suffer 'industrial' service where they are run down daily and recharged nightly.
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Nearly true (Sometimes the cart gets a day off)
But if I'm boondocking.. That is almost exactly how my batteries live,, Run 'em down every night, and charge 'em up every day I do.
So.. other than flipping day and night.. What's the difference?
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Home is where I park it!
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12-27-2009, 08:04 PM
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#24
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Senior Member
Monaco Owners Club
Join Date: Nov 2008
Location: Melbourne & Marathon, Florida
Posts: 1,537
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Wow, this is way more complicated than my pea brain can absorb. I have four of them and I check them once a month for fluid level and top off with distilled water. When they do go bad I will replace them, they only cost $300.00/set. I have spent more than $300.00 on do-dads. I worry more about expensive stuff that can kill me!
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2005 Safari Cheetah 38PDQ - 2009 Ford Flex
Me (Gatogonow), The Boss (DW), Honey Bunny, Maggie May and Mollie Kay (The Gatos)!
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12-27-2009, 11:30 PM
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#25
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Senior Member
Join Date: May 2007
Posts: 632
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re: "But if I'm boondocking.. That is almost exactly how my batteries live,, Run 'em down every night, and charge 'em up every day I do." - the thing is, if your usage is like a typical Rver, you don't "Run 'em down every night." The battery usage is nowhere near as consistent as it is with industrial equipment. Your needs for reserve capacity are much greater than it is for golf carts. Most off-grid full timers also do not have the battery charging capacity that can reliably assure a complete battery charge (12+ hours). -- the issues are not simple and are worth a good discussion on their own. I'd love to see some decent data logs of energy in and out plotted daily for a period of a couple of years or more for a statistically significant population size of off-grid full time RVers to get an idea of just how much use varied, how complete charges were in a typical diurnal cycle, and such things. The sample would have to be big enough to gain some credible correlations and to provide insight into battery life and failure causes to be really useful. As it is, we can't even get good long term reliable temperature measurements ...
but again, it is another point of argument that is specious and does not contribute to anything other than illustrating just how deep the digging can go when data and reliable measure are not available to support the cause.
Quote:
I have spent more than $300.00 on do-dads. I worry more about expensive stuff that can kill me!
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now that is a perspective on the issue I can get a handle on. A friend of mine figured that his best peace of mind for a 2 battery system was to buy new ones every year or two (~$120 expense) - and that was after he replaced his converter with one that would do decent charging as well as good battery storage maintenance. But at least he knows what he is doing and doesn't try to sell others on things not supported by evidence and measure.
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12-28-2009, 08:32 AM
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#26
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Senior Member
Monaco Owners Club
Join Date: Apr 2008
Location: Oak Ridge, TN
Posts: 329
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Wow!! "... people trying to use many inane esoterica from them to try to resolve their cognitive dissonance ...". My MIT PhD brain is still reeling and trying to understand this one. Guess us Tennessee boys just have to work harder to figger out these two dollar words.
(MM you can delete this off topic note if you wish. Sorry, I just couldn't resist.)
Lew
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[SIGPIC][/SIGPIC]
2016 Winnebago Cambria 30J
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12-28-2009, 09:37 AM
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#27
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Senior Member
Join Date: May 2007
Posts: 632
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re: "Tennessee boys just have to work harder to figger out these two dollar words." -- this is a good illustration of the approach often used when encountering these battery discussions. I'd suggest that it would be a better approach to grab a dictionary and do a bit of research. That's a bit more effort but definitely more productive than belittling or ridiculing - and a lot more sociable as well.
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12-28-2009, 10:53 AM
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#28
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Senior Member
Monaco Owners Club
Join Date: Apr 2008
Location: Oak Ridge, TN
Posts: 329
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My apologies BrianL. It was my attempt at humor and I had no intent to belittle or ridicule. As my wife keeps telling me, "Engineers should not attempt humor." Well she is right in my case. No slight intended, please accept my apologies.
Lew
__________________
[SIGPIC][/SIGPIC]
2016 Winnebago Cambria 30J
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