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08-19-2012, 03:31 PM
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#1
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Rivet Master
1964 19' Globetrotter
South Kingstown
, Rhode Island
Join Date: Dec 2004
Posts: 1,406
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AGM battery replacement
On to the next project: replacing the Univolt with an Iota DLS 55, and replacing the battery with an AGM type. We don't have great separation between the battery compartment and the coach, and I want something that doesn't off gas and is stable, no possibility of leaking acid etc. My big question is this: what size should I get? We have a stock standard 1964 Globetrotter, electric start for the fridge, 12 lighting and that's about it. We use the old gravity furnace and will be replacing the water heater with, I guess, an electric start model, although I like the idea of the simpler pilot version. Any help would be great thanks
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Wherever you go, there you are
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08-19-2012, 03:31 PM
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#2
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Rivet Master
1964 19' Globetrotter
South Kingstown
, Rhode Island
Join Date: Dec 2004
Posts: 1,406
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btw, I'm having someone replace the Univolt, not tackling it myself.
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Wherever you go, there you are
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08-19-2012, 05:29 PM
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#3
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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You don't say what Group number the present wet-cell battery is, so it's hard to guess about an AGM replacement. You should be able to go with the same group number (Group 24, or Group 27, or whatever) since batteries in the same Group tend to have similar dimensions.
However, it might be better to simply take the dimensions of the battery compartment, and get the largest Group number batteries that will fit (don't forgert to check height, too). But check the available amp-hours as well. My memory is telling me that larger Group numbers usually have higher amp-hours, but my memory has lied to me before. You always want the greatest number of amp-hours you can get.
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I thought getting old would take longer!
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08-19-2012, 05:42 PM
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#4
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Master of Universe
2008 25' Safari FB SE
Grand Junction
, Colorado
Join Date: Sep 2007
Posts: 12,711
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The higher the Group number, the more ampere hours from a specific brand. You can check battery dimensions on the manufacturer's website and see if it fits in your battery box. Make sure there's enough room for the cables and they aren't rubbing against any metal—eventually the insulation will wear and cause a short.
I'd get the one with the most ampere hours that will fit. New Airstreams come with Group 24—smaller and cheaper. We upgraded to Lifeline Group 27 and had to make some modifications to the box.
Gene
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08-19-2012, 06:16 PM
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#5
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Rivet Master
Join Date: Jan 2005
Posts: 811
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AGM's breath also. They are vented like flooded cell batteries.
I had AGM's and went back to flooded cell. My last two sets of agms didn't last any longer than the flooded cell and were double the price.
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08-19-2012, 08:40 PM
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#7
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Rivet Master
1964 19' Globetrotter
South Kingstown
, Rhode Island
Join Date: Dec 2004
Posts: 1,406
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I don't know what was stock, I think it's a 27 now.
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Wherever you go, there you are
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08-20-2012, 11:43 AM
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#8
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Master of Universe
2008 25' Safari FB SE
Grand Junction
, Colorado
Join Date: Sep 2007
Posts: 12,711
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I looked over the Airstream website for all but Sport models and all it says about batteries are "lead acid". Nothing about Group. I would assume they are still using Group 24 because they are cheaper. If the solar option is to go to AGM's and Group 27, that is the exception.
Gene
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08-20-2012, 02:25 PM
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#9
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1 Rivet Short
1989 25' Excella
By The Bay
, Rhode Island
Join Date: Apr 2006
Posts: 1,620
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Quote:
Originally Posted by handn
AGM's breath also. They are vented like flooded cell batteries.
I had AGM's and went back to flooded cell. My last two sets of agms didn't last any longer than the flooded cell and were double the price.
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Curious what you have for a charger/converter?
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*Life is Good-Camping all around the Continent*
*Good people drink good beer-Hunter S Thompson*
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08-20-2012, 02:33 PM
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#10
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Figment of My Imagination
2012 Interstate Coach
From All Over
, More Than Anywhere Else
Join Date: Dec 2011
Posts: 10,868
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Quote:
Originally Posted by handn
AGM's breath also. They are vented like flooded cell batteries.
I had AGM's and went back to flooded cell. My last two sets of agms didn't last any longer than the flooded cell and were double the price.
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AGMs don't last longer. Their main benefits as house batteries is that you can discharge them more slowly, and discharge them more deeply without hurting them, than typical wet-cell batteries.
__________________
I thought getting old would take longer!
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08-20-2012, 04:06 PM
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#11
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3 Rivet Member
1965 20' Globetrotter
1955 22' Safari
Butte
, Montana
Join Date: Mar 2009
Posts: 145
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I purchased an Optima Blue top because their warranty is longer than the other ones I looked at. I've only had it since June. So far , so good.
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08-21-2012, 08:39 AM
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#12
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Rivet Master
2015 28' Flying Cloud
Durango
, Colorado
Join Date: Oct 2010
Posts: 623
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Actually, AGMs do not breathe just like flooded cell batteries, and can last much longer. The differences are significant. Battery performance and life depends upon many factors - depth of discharge, recharge rates, temperature, self-discharge during storage, maintenance, etc. It's worth some research before making a replacement decision. The Lifeline site Lifeline Batteries - Marine & RV Deep Cycle Batteries provides good information. I've just replaced my original Interstate group 24s. (failed at 16 months!) with GP 24 AGMs. I've used Lifeline & Rolls AGM's on my cruising sailboat, but chose XPower AGM's from Batteries Plus for the same specs as Lifelines but a much better warranty (full replacement to 4 years - many retail outlets across the USA). For the seasonal usage of our cruising boat and Airstream, I've found that the difference in initial cost of AGM's to be good value in the long run.
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Safe Travels,
Joe & Joan Donnaway
Durango, CO
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08-21-2012, 10:22 AM
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#13
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Rivet Master
1964 19' Globetrotter
South Kingstown
, Rhode Island
Join Date: Dec 2004
Posts: 1,406
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Thanks Jamu. I've been reading and have come to the conclusion that the AGM is the way to go for our application. Even though AGMs breathe, it's a small amount by comparison to more conventional lead acid batteries, and they're suitable for use in enclosed, ie habitable, spaces (like ours) Thanks for the info on the Xs battery, and Batteries Plus.
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08-31-2012, 02:13 PM
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#14
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Rivet Master
Join Date: Jan 2005
Posts: 811
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Quote:
Originally Posted by BillTex
Curious what you have for a charger/converter?
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I had a the ever popular, battery killing Paralax 7355. I upgraded to a three stage bolt in converter charger and went from agm's to flooded cell group 24's because I got tired of paying up for batteries that didn't last. We will see how long the new ones last.
I don't think agms last any longer than flooded cells and the flooded cell
batteries cost less than half.
My old agms had little vents on the top. Aren't the vents for breathing?
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08-31-2012, 02:51 PM
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#15
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Moderator
2017 26' Flying Cloud
Alamo Heights
, Texas
Join Date: Aug 2006
Posts: 8,523
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AGMs do breathe a little, but generally they're set up in a "non spillable" form factor so what venting they have prevents liquid from passing and they have somewhat more durable internal construction than traditional lead-plate-in-liquid batteries.
I'm still using a wet battery for the trailer's Group24, but I bought a big AGM to run an inverter for my CPAP so I won't be paranoid about having it inside the trailer, and because I'll probably discharge it pretty heavily when I'm using it. I think a wet cell will do pretty well there except for serious boondockers, especially in terms of price per amp-hour.
Where an AGM really, REALLY made a difference for me was on my motorcycle. I had a big air-cooled Yamaha FJ1200 and they put the battery just aft of the cylinders, so in addition to the vibration of a motorcycle it was always being cooked by engine heat. Flooded batteries never lasted 2 years, but I bought a single Westco AGM that lasted for 8 and was still on the bike when I sold it.
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— David
Zero Gravitas — 2017 Flying Cloud 26U | WBCCI# 15566
He has all of the virtues I dislike and none of the vices I admire. — Sir Winston Churchill
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09-01-2012, 07:39 AM
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#16
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Rivet Master
2015 28' Flying Cloud
Durango
, Colorado
Join Date: Oct 2010
Posts: 623
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Re: Breathing. An AGM is valve-regulated, and emission of hydrogen gas is negligible unless the battery is severely overcharged. Perhaps that was the issue in your bad experience with AGM's? Was the Paralax charger left on for extended periods? As an AGM self-discharges only 1-3% per month, (vs 5-10% per month increasing with age for flooded batteries) it is good practice to disconnect the charger after the battery is fully charged, unless it is a 'smart charger' that self-regulates to 'float mode' which is temperature-dependent. The Paralax does not provide such. Your new 3 stage charger may do this. Does it have a battery temperature sensor? I use a BatteryMinder 12248 on my large bank of AGM's on our sailboat during our six-month storage season, and plan to do the same with the new bank of AGM's in the Airstream. The general consensus among cruising sailors who leave or store their boats for extended periods, is that quality AGM's (such as Lifeline or Rolls), with minimal maintenance, last for many many more cycles than flooded cell batteries.
__________________
Safe Travels,
Joe & Joan Donnaway
Durango, CO
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09-01-2012, 01:16 PM
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#17
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Rivet Master
Join Date: Jan 2005
Posts: 811
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I have 4 8d's on my boat to run the house. Engines have seperate start batteries. The 8d's are agm's for the reason that they are very difficult to get at to check for water. They are going on 4 years which is a good thing as they cost an arm and a leg. The start batteries lasted just four years and they were flooded cells.
The 8d's do have temp probes as part of the the Xantrex inverter, charger.
I am not sure a temp probe is a good idea for an Airstream. The batteries sit inside a metal box in the sun for part of the time. Charge could be cut off even if needed because the sun warms up the batteries fooling the temp probe into thinking that they were charged.
I have a 10 amp solar charger which I don't know much about as it was on the trailer when I purchased it. There is a gauge for volts but I don't know about a regulator, nor is there a brand name on the solar charger.
Am I overcharging my batteries by running both the converter (three stage with trickle) and the solar?
I don't know any way to check except by prying the caps off the supposedly maintence free batteries and checking for water usage. Does anyone know another way to check?
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09-02-2012, 09:22 AM
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#18
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Rivet Master
2015 28' Flying Cloud
Durango
, Colorado
Join Date: Oct 2010
Posts: 623
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handn,
My battery box sees little direct sunlight, either shaded by the trailer or propane tank cover for most of the time, and I also carry a toolbox (I fitted corner brackets to the battery box lid) that covers the battery box (with padlocks to secure both toolbox and battery box). The recommended float voltage for Lifeline AGM's ranges (for common camping temps) from 14.08v @ 30º to 13.02v @ 100º. I still have the dumb Paralax charger, but most of our camping save for quick overnights on the road is off-grid, and my multi-stage BlueSky MPPT solar controller does have temp compensation. I should think that you are ok with both of your chargers operating in float range, it's the Paralax that I wouldn't leave operating for longer periods. I use the BatteryMinder for longer-term storage in both the Airstream and the sailboat.
For testing the batteries & charging system, I use this very handy tester SOLAR BA7 100-1200 CCA Electronic Battery and System Tester. Available at Amazon.com
__________________
Safe Travels,
Joe & Joan Donnaway
Durango, CO
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09-02-2012, 03:37 PM
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#19
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Master of Universe
2008 25' Safari FB SE
Grand Junction
, Colorado
Join Date: Sep 2007
Posts: 12,711
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Handn,
A solar system should also have a multistage charger integrated into the controller module. Check the instructions or company website to see if it does.
If you are plugged into shore power, the trailer converter will handle (over)charging the batteries. If you are not plugged in, the solar controller will handle it. If you have a one stage converter, leave the trailer unplugged and the solar charger should keep the batteries topped up properly.
Gene
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09-04-2012, 10:49 PM
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#20
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3 Rivet Member
2012 27' Flying Cloud
Denver
, Colorado
Join Date: Mar 2009
Posts: 102
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Oh no! I'm afraid we've toasted our AS batteries! We seem to have less juice despite dlligently reducing our use. And even though we've been using a solar panel to keep them charged every day there seems to be less juice to go around. We can charge up to 15.0 volts and one LED light will drain it to 8.0 volts in an hour. Doesn't seem right. It seems no matter how conservative we are, the volts drop to 8 or less every night. I know that's not good, either. Oh, yes, and to be totally honest we did drain the batteries to zero last month (use that Storage switch just in case you've left a little light on in the back of the trailer) and charged back up with a car charger and solar panel.
Have we toasted our batteries? Say it ain't so?
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Jim and Marsha
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