Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-11-2010, 10:32 AM   #29
INSANITY CENTRAL
 
doorgunner's Avatar
 
1986 32' Excella
2014 Interstate Ext. Coach
Citrus Heights , California
Join Date: Aug 2006
Posts: 2,105
Images: 35
Aolani--

my 2 sixers are looking forward to meeting your 2 sixers at JRRV this upcoming October.

I can relate to this thread- 2 sixers =1 twelve pack. it's about beer isn't it?
__________________

__________________


www.popasmoke.com




Proud Appellation American





Vine View Heights is now closed.

YETI ( 65 Quart )

IGLOO (Ice Cube, 50 Quart )
doorgunner is offline   Reply With Quote
Old 05-11-2010, 10:53 AM   #30
2 Rivet Member
 
1969 31' Sovereign
Mount Vernon , Washington
Join Date: Mar 2010
Posts: 35
Quote:
Originally Posted by overlander63 View Post
Yes. A pair of angle iron channels running across the A frame the width of the battery, with the positive and negative terminals connected through the umbilical to the tow vehicle would hold the battery to the A frame, and connect it electrically. I remember your '69 having a manual tongue jack, with a horizontal crank. You could either go with an electric jack or a manual jack with a vertical crank to gain some inches, and move the LP tank mount slightly forward. This will give you room for the group 31 battery. There are two types of group 31, you would want the one with the threaded posts.

Now, I work on these things every day, so what may be a hour or two project for me may be an all day project for many people. "Measure twice, cut once".
OK! I took a look, just now. I see there's more room than I thought! Also, thanks to the original owner who went all out, I have a working electric tongue jack so that's not an issue. I still want to wire the batteries through an isolation switch, so I may not wire the lone 12 v through the umbilical. A doctor friend of mine, who has a 25' AS recently did something similar. He put the batteries forward of the LP tanks, though, then built an aluminum (or stainless?) doghouse to cover everything. If he ever has to turn sharply he'll hit it with the TV bumper... he's usually a lot brighter than that. I'm surprised he didn't think of moving the LP forward. I like your idea a whole lot better.
Now.... where can I lay my hands on a welder???.....
__________________

__________________
Ellie & Carl is offline   Reply With Quote
Old 05-11-2010, 11:16 AM   #31
Don't forget your cat nap
 
Ag&Au's Avatar
 
Port Orchard , Washington
Join Date: May 2009
Posts: 4,464
Images: 1
Lightbulb Let's make a 45 degree course change

Welcome Heavenly Cloud. (meaning of Hawaiian word Aolani).

You will find that that the forums have certainly sacred topics. You are correct that they border on religion. I could tip you off on what some others are, but it is much more fun to stumble into them yourself.

Since this topic seems to have reached the impasse typical of our para religious subjects, I would like to change the direction somewhat, since all the battery fans are now gathered here.

What happens if two 12 volt batteries (be they 1 12v or 2 6V) of different capacities or characteristics are operated in parallel?

This is an actually question I have. I am not trying to stir things up. (really )

Regards,

Ken
__________________
Ag&Au is offline   Reply With Quote
Old 05-11-2010, 11:28 AM   #32
VAC President
 
Buttercup's Avatar
 
1977 27' Overlander
1954 25' Cruiser
1990 34.5' Airstream 345
VC Highlands , Nevada
Join Date: Mar 2005
Posts: 2,149
Send a message via Skype™ to Buttercup
Aolani,

You have done quite well for your first 3 posts. They are informative, substantive and describe your personal experience quite well. Despite the protestations of others who might try to portrait themselves as more knowledgeable than you for any topic, your experiences suggest that your new configuration is working exactly as you hoped. You are satisfied with the results so there is really nothing you have done wrong. You are obviously educated more than others in areas and have researched the topic thoroughly. I for one appreciate your contribution to this forums, especially on this topic. I understood that you were not trying to sell snake oil to everybody else, you were just sharing your experience, which may work for others, or it may not.

Quote:
Originally Posted by Mexray
For those considering adding one additional 12 battery in parallel to the existing battery bank - make sure it is of the same GROUP size - mixing battery group sizes will result in different individual cell sizes, causing the batteries to charge and discharge at different levels - usually the larger cell battery never gets fully charged...

The age of the batteries should also be taken in account, as cell capacity is diminished with age - if you install a new battery with the same group, but the existing batteries are say, three years old, you will have different cell capacities due to age - if adding a third battery, I'd say only if your existing batteries are less than a year old - otherwise replace all three at the same time..
This information is very true as anybody who is either living, or planning to live off grid knows, you must factor this in when designing your system. Driving down the road charging your batteries doesn't mean a thing that is just for convenience. The charge you get from your vehicle may not even fully or properly charge your battery compared to say a 3 stage charger (a starting battery and a deep cycle battery are constructed differently and therefore charge, discharge and perform differently).

And the age and type of battery makes a difference also. An older battery will have plate sulphates built up, and therefore a higher internal resistance, which means that they will not charge as fully as a newer, fresher set of batteries. End result, lower capacity.

I may be preaching to the choir as you are an electrical engineer and therefore must already know these basic facts probably better than most. So, nice job for your first 3 posts hope the next 2000 are equally as informative.
__________________
Buttercup's Web Site. WBCCI #17330, 11281 & 7830. VAC Past President, TAC NV-2 & NV-3
Buttercup is offline   Reply With Quote
Old 05-11-2010, 11:52 AM   #33
Don't forget your cat nap
 
Ag&Au's Avatar
 
Port Orchard , Washington
Join Date: May 2009
Posts: 4,464
Images: 1
Oh Oh

Quote:
Originally Posted by w7ts View Post
.........................................
What happens if two 12 volt batteries (be they 1 12v or 2 6V) of different capacities or characteristics are operated in parallel?

This is an actually question I have. I am not trying to stir things up. (really )

Regards,

Ken

Whoops, Sorry, I obviously didn't read Mexray's post.

At least its not the first time I did something goofy here.

Regards,


Ken
__________________
Ag&Au is offline   Reply With Quote
Old 05-11-2010, 12:00 PM   #34
Rivet Master
 
tkasten's Avatar
 
1965 22' Safari
Vassar , Michigan
Join Date: Jun 2009
Posts: 847
Images: 6
6v Batt.

Aolani,

Welcome. I have read all of the posts to your thread - wow! Some of these folks get a bit passionate. I think you have done a fine job with your homework. Boon-docking I have found that good basic energy conservation brings good results no matter what batteries you use. I use 1 group 27 in our 65 22' Safari. As a habit we use lights sparingly. Run the furnace when cold mostly in the morning. We do not use a microwave. The fridge runs on propane. We typically get 4 to 5 days from one charge. I have another group 27 that powers our Tel/Sat. and that one gets more drain/charge use than the trailers battery. We have a Honda 3000 in back of our TV and that handles charging and air conditioning.

Best of luck..........Tim
__________________
Tim
TAC MI 14

Everyday is a Saturday
tkasten is offline   Reply With Quote
Old 05-12-2010, 09:49 AM   #35
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
Quote:
What happens if two 12 volt batteries of different capacities or characteristics are operated in parallel?
Each provides energy and accepts charge in proportion to its capacity as long as they are the same chemistry (lead acid in this discussion).

Whether a battery is big or little, old or new, its voltage will track over the same range if it is the same chemistry.

When batteries are connected in parallel, the connection point must be at one voltage common to all batteries connected there.

This means that, when batteries are connected in parallel, you can't discharge one below the state of charge of the other or charge it above the state of charge of the other.

Usual caveats apply. There are some so hot on this one they start coming up with terminal resistance and other interesting phenomena but those factors are insignificant in the overall scheme of things.

So why the recommendation to keep all batteries in a bank as similar as possible? Because it will tend to more evenly 'wear' the batteries in the bank and otherwise spread out loads and currents to get best, and most predictable, performance over time. As with anything batteries, though, there is a lot of leeway so getting overly obsessed with battery equality is not really needed.
__________________
bryanl is offline   Reply With Quote
Old 05-14-2010, 02:11 PM   #36
VAC President
 
Buttercup's Avatar
 
1977 27' Overlander
1954 25' Cruiser
1990 34.5' Airstream 345
VC Highlands , Nevada
Join Date: Mar 2005
Posts: 2,149
Send a message via Skype™ to Buttercup
According to the guidelines from professional installers of battery systems, the above advise is not very wise. Here’s why… Most flooded batteries should be charged at no more than the "C/8" rate for any sustained period. "C/8" is the battery capacity at the 20-hour rate divided by 8. For a 220 AH battery, this would equal 26 Amps. If the pair of batteries connected in parallel (or series for that matter) has appreciable differences due to age, capacity or type of battery, you will only damage your battery pair trying to meet these requirements.

Unfortunately, despite what some might suggest here, batteries banks do not simply self charge properly if you give them one voltage – depending on the age, construction and amount of internal resistance; they will not charge proportional to their capacity. That is a fallacy. As an anecdotal story, I am sure many have known someone who has a dual battery system in their truck and one of those batteries is dead as a doornail but they were connected in parallel and charged at the same voltage. How can that be? As the internal resistance of one battery goes up, the overall resistance of the pair goes up. As that resistance goes up, the charging voltage of the batteries & charging system goes up and the other battery received a disproportionate amount of charge. The battery with the higher internal resistance takes a lesser charge and over time sulfation builds up on the plates to a greater extent, which compounds the problem. Eventually the battery just has no real usable capacity because it’s internal resistance (due to plate degradation) has gone up too high. You can measure the voltage across that battery and it may appear fine, but put a load on it and it drops off the face of the earth. This is why load testing a battery is one of the best ways of testing a battery’s ability to deliver load.

Any reputable battery maintenance site, will tell you the following: (I got this off a professional battery system installer’s web site but you can verify this yourself)
Quote:
In situations where multiple batteries are connected in series, parallel or series/parallel, batteries should be the same size, type and manufacturer (if possible). Age and usage level should be the same as the companion batteries. Do not put a new battery in a pack which is more than 6 months old or has more than 75 cycles. For long life batteries, you can have up to a one year age difference.
Hey, isn’t this what just about what MexRay said??? I found this information from a reputable source on the internet – a battery vendor / installer. Bottom line - readers on these forums need to research the information presented here and avoid being hornswoggled by unsubstantiated or “IMHO” styled advice from anybody replying on the forums. I have seen too many cases where someone has given me information on how some system works on my trailer that is patently wrong. The lesson I have learned from ill advice is that one needs to be a critical reader when it comes to things technical in these sorts of discussions. Research it yourself, independent of what any self-purported “expert” says here. In the case of batteries, I am no expert. However, I have maintained deep cycle battery systems as a volunteer effort I was involved in for several years before I ever got my first trailer. That experience taught me plenty. The best information I got about my battery bank was from the manufacturer.

I would always refer to the manufacturer of your particular brand for the true guidelines of pairing, use and maintenance (including charging) of your particular battery bank, afterall, they made them – they are the REAL experts on them. And from what I have seen online from several sources, matching batteries is the least expensive way to maintain your battery system. But don’t take my word for it – check it out yourself.
__________________
Buttercup's Web Site. WBCCI #17330, 11281 & 7830. VAC Past President, TAC NV-2 & NV-3
Buttercup is offline   Reply With Quote
Old 05-15-2010, 10:32 AM   #37
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
re: "they will not charge proportional to their capacity. That is a fallacy." -- perhaps you need to have a talk with professor Kirschoff (wikipedia).

re: "As that resistance goes up, the charging voltage of the batteries & charging system goes up" -- Managing charging voltage is the means by which modern battery chargers control their action. This is important for RV's as you don't want too high a charging voltage as a protection for connected appliances. It is also important for optimal charging with modern 3 stage chargers and one of the factors that distinguishes them from old style current limited battery chargers.

The fact that the resistance of a battery changes with its state of charge is very much related to the mechanism that proportions charge as it is the battery with the lower state of charge that has less resistance in the circuit and will receive the most current. It is like filling a big bucket and a small one when they are connected at the bottom. The fill level for both stays the same as you fill them.

For those who aren't EE types and familiar with circuits and battery models, there are other ways to look at this. One I mentioned is the fact that state of charge is directly related to voltage. That means that only the state of charge is determined at the common point where batteries are connected together because you can't have one point in a wire with multiple voltages.

The other fact to consider is that most of us connect our tow vehicle battery in parallel with the trailer battery when traveling down the road. If all the dire warnings about parallel batteries are true, then we'd all be suffering rather than charging our trailer batteries while traveling.

A third issue to keep in mind is that things in actual practice are not always as cut and dried and some may wish. Available battery capacity can vary by up to 20% from such things as temperature, cycle to cycle variance, use profile and age so pretending a better accuracy than this does not reflect real conditions. In this context, it means that, yes, matching batteries in a bank is probably a good thing but, no, there is no need to get fanatical about it.

Quote:
But don’t take my word for it – check it out yourself.
The key here is to make sure you have definitions that are objective and measurable and that you base your conclusions on sound measure and appropriate consideration for circumstances. All too often someone's sayso is substituted and that only propagates false myths. Watch out for those who start shouting and insisting on absolutes based on authority rather than on actual measure and understanding of the underlying concepts.
__________________
bryanl is offline   Reply With Quote
Old 05-15-2010, 06:54 PM   #38
VAC President
 
Buttercup's Avatar
 
1977 27' Overlander
1954 25' Cruiser
1990 34.5' Airstream 345
VC Highlands , Nevada
Join Date: Mar 2005
Posts: 2,149
Send a message via Skype™ to Buttercup
Nice link to Wikipedia, but that only represents half the story really. To complete the picture, factor in the battery’s internal resistance and perhaps you will have a better understanding - Internal resistance - Wikipedia, the free encyclopedia
Thought experiment – 2 batteries, one 100 Ah and another 200Ah. The 200Ah battery is older and has a higher level of plate sulfation and therefore it’s internal resistance is higher by even a few miliohms. Which battery will take a higher proportional charge (that would be in relation to its rated capacity) assuming all other factors being equal?
Quote:
It is like filling a big bucket and a small one when they are connected at the bottom. The fill level for both stays the same as you fill them.
In the above example, having 2 different capacities is one thing, but having 2 different batteries (with or without the same rated capacity) with differing internal resistances is completely another. The example is incomplete and too simplistic because batteries are actually more like buckets with a small weep hole in them (to represent the self discharge qualities of the battery and a dump valve on the common line between them to represent the normal load draw. The internal resistance of the battery would be like an obstruction in one of the buckets fill/drain line but not the other. During filling (charge) the bucket with the lower resistance will fill more quickly (up to the level of the source if you will). The other bucket will not fill as quickly and in fact could be nearly empty. Being as the water supplied to the buckets can only be measured at the fill line (which is analogous to the terminals on the battery) the bucket will appear to be full, but will not be. (note, this is where a gravity test of the battery acid might give you a clue that here are problems in paradise).
Quote:
For those who aren't EE types and familiar with circuits and battery models, there are other ways to look at this. One I mentioned is the fact that state of charge is directly related to voltage. That means that only the state of charge is determined at the common point where batteries are connected together because you can't have one point in a wire with multiple voltages.
I’ll be the first to admit I am not a EE, but I have had years of self taught electricity and electronics starting from the time I went into the NAVY until present day (when you are out to sea for 6 months at a time, you have lots of time to read lots of training courses). What I do know is this – it is not at all a fact that state of charge is related to voltage alone as suggested above. It is a function of the quality of the acid in the battery, the amount of plate sulfation present IN the battery, the amount of debris at the bottom of the battery, the age of the battery and the temperature of the battery at time of charge & the depth of discharge the battery experiences throughout its lifetime. All of these factors obviously contribute to the quality of charge a battery receives.
Quote:
The key here is to make sure you have definitions that are objective and measurable and that you base your conclusions on sound measure and appropriate consideration for circumstances. All too often someone's sayso is substituted and that only propagates false myths.
This is exact what Aolani did in his first post. Described a problem, described his first attempts to resolve the problem, described his reanalysis of the continuing problem, came to a conclusion on how to finally solve the problem for himself and implemented that solution. It worked perfectly for him. He didn’t need somebody to suggest that his solution was some sort of misleading solution designed to :
Quote:
hornswoggled into spending a whole lot of money on things they may not really need
.
Quote:
Watch out for those who start shouting and insisting on absolutes based on authority rather than on actual measure and understanding of the underlying concepts.
I am just not sure what you are referring to here….
__________________
Buttercup's Web Site. WBCCI #17330, 11281 & 7830. VAC Past President, TAC NV-2 & NV-3
Buttercup is offline   Reply With Quote
Old 05-15-2010, 10:29 PM   #39
3 Rivet Member
 
hshovic's Avatar
 
2007 25' Safari FB SE
Bozeman , Montana
Join Date: Apr 2007
Posts: 222
Images: 20
I hope you changed your converter also. I found I had to do that to avoid overcharging the AGM's. The factory converter/charger is not adequate for the 3 stage needs of those batteries.
__________________
Hank
WBCCI 1489 AIR 20708
2015 Chevy 3/4 ton 4 x 4 gas; 2007 Safari FB SE
"Its better to light just one candle than to curse the darkness,
Unless you're blinded by the light..."
hshovic is offline   Reply With Quote
Old 05-15-2010, 10:42 PM   #40
2 Rivet Member
 
rustyrivet's Avatar
 
2005 22' Safari
Gresham , Oregon
Join Date: Jul 2008
Posts: 73
I find all this very interesting. Before settling on batteries I got on-line and read all could find on batteries and capabilities. After much research I decided to stick with 12 volt batteries made by life line. I called Lifeline and talked to Justin Godber regarding matching a series 24 Lifeline battery with a series 27 battery. He told me there would be absolutely no problem as long as they were the same manufacturer and the same vintage of battery. I purchased two Lifeline batteries, one a series 24, the other a series 27 based upon that advice. That was two years ago. So far, no problems. Justin also told me that for recharging purposes, no slow charge was necessary on Lifeline batteries; that I could recharge with a full 180 amps if I needed to. I have never done that, but it was interesting to note that it was possible. Maybe all batteries aren't created equal. jc
__________________
2005 22 ft Safari LS
2009 Toyota Tundra
Hensley Hitch
Lifeline AGM's
rustyrivet is offline   Reply With Quote
Old 05-16-2010, 12:53 AM   #41
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
re: "To complete the picture, factor in the battery’s internal resistance" -- That is what makes connecting two batteries in parallel 'share the load.' The voltage relationship to state of charge is one way this internal resistance is expressed.

Issues of self discharge are only at issue out of the context here. As I understand it, we are talking about batteries in reasonably active use, not batteries stored without any proper maintenance for periods longer than a week. Self discharge is only an issue if you have batteries of significantly different age or of somewhat different type (sealed versus wet cell, for instance) setting without any activity for quite a while.

re: "it is not at all a fact that state of charge is related to voltage alone as suggested above."
Again, context. We are talking RV's here and a level of precision appropriate to typical battery use in that context. We need to avoid the 'reduce to the absurd' logical fallacy if we want to learn anything useful.

Specific gravity and voltage versus state of charge charts are quite common on the web. I do know that voltage, like specific gravity, needs to be properly measured. One of the more interesting websites on this topic is SmartGauge Electronics - battery metering as that device depends upon matching current and voltage curves to determine state of charge in a dynamic environment (he's got some very good tech notes on battery bank wiring and configuration with explanations as well). Most of us have to let the battery get to a rest state to obtain reliable measure.

Quote:
I found I had to do that to avoid overcharging the AGM's.
That is one caveat with using AGM's in an RV. Like other sealed battery types, they are sensitive to overcharging. That often means no equalizing (which most RVers don't need to be concerned about anyway due to their use patterns) and also the storage float levels need to be carefully matched to manufacturer's recommendations. AGM's are nice batteries and can provide an extra year or two of life over wet cells but they should still be in a properly vented battery box and they do need some care about charging voltages. The Lifeline series has become much more tolerant of RV charging systems than they used to be from what I can tell, which is nice.

Quote:
no slow charge was necessary on Lifeline batteries;
Another nice feature of AGM's - low internal resistance. That can be handy when using inverters as well. But keep in mind that trying to get large currents into a battery to charge it means a rather high charging voltage and that may not be good for other things connected to the battery. Also keep in mind that even AGM's will still need 8 to 12 hours to charge fully, even if you do a high current bulk charge phase. It is that last five or ten percent that take time and it is that last bit that can make a big difference on your battery life.

Any battery charging that runs in excess of 20 amps for every 100 amp hours of battery needs a charger with a temperature probe and the smarts to avoid thermal runaway. That usually isn't an issue in the typical RV setup because, even if the converter/charger can supply the current, it won't run the voltage up high enough to provide that much current for more than a few minutes.

re: "He told me there would be absolutely no problem as long as they were the same manufacturer and the same vintage of battery." -- did he tell you what the problem was if you used same type but different manufacturer or perhaps batteries whose age was a year or two apart? That is what is hard to define, just what the problem really is and its impact on what you want to do. Unless you get to extreme cases or absurd levels of precision, that 'problem' is not of much, if any, significance else we couldn't charge our trailer batteries from the tow vehicle.
__________________
bryanl is offline   Reply With Quote
Old 05-16-2010, 05:20 AM   #42
4 Rivet Member
 
1966 30' Sovereign
1963 22' Safari
orlando , Florida
Join Date: Jun 2006
Posts: 280
Images: 9
I have a 12v deep cell battery.It is 8 years old.It provides enough watts to power a 12v light so I can read a Zap comic book at night.My portable radio has two AA batteries.The hot water and heater are LP gas.The 6v set up is a great idea,but chances are if I had all that reserve power I would forget to come home.Call me Old School but I like camping the simple no hassle way.I wasn't there, but I hear poor old Wally didn't even have a BIC lighter and traveled the world!
Attached Thumbnails
Click image for larger version

Name:	work 219.jpg
Views:	75
Size:	278.2 KB
ID:	102615  
__________________

__________________
richie rich is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
What an amazing service matthews Member Introductions 14 11-11-2006 08:40 PM
Switched to a motorhome! 48-remi Member Introductions 2 02-01-2006 07:46 PM
Heat pump switched on in AC mode Pahaska Furnaces, Heaters, Fireplaces & Air Conditioning 11 05-22-2005 09:09 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 08:01 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.