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Old 08-31-2012, 03:51 PM   #15
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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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Old 09-01-2012, 08:39 AM   #16
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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.
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Old 09-01-2012, 02:16 PM   #17
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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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Old 09-02-2012, 10:22 AM   #18
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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 @ 30 to 13.02v @ 100. 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
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Old 09-02-2012, 04:37 PM   #19
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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.

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Old 09-04-2012, 11:49 PM   #20
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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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Old 09-05-2012, 09:58 AM   #21
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Are these flooded batteries? Are they properly watered? Either purchase a quality battery tester, or remove the batteries and take them to your preferred battery store to have them tested. It's probably time to shop for replacements.
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Old 09-05-2012, 02:55 PM   #22
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Jim, if those are the original batteries, you got 4-5 years out of them and that's about average. 8 volts is well below 50% charge, in fact, it is below 0% charge. The batteries are not holding a charge and you can test them with a hydrometer, and I expect you will have more than 1 dead cell in each battery.

Ours lasted almost 4 years and we replaced them with series 27 Lifeline AGM's. That's a big investment, but it should pay off as they are supposed to last a lot longer than the OEM series 24's. To install Group 27's, you will have to trim off a lip on the battery box.

Do yourself a favor and replace the converter with one with a multistage charger to protect the batteries.

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Old 09-05-2012, 04:04 PM   #23
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.................................

, and I expect you will have more than 1 dead cell in each battery.

....................................

Gene
Not that it matters at this point, but one of the batteries may still be capable of holding a charge to some extent. If two batteries are wired in parallel as they are in an Airstream, the voltage will always be that of the weakest battery, because it will draw the good battery down until they are equal. In any case I'm sure they are both beyond salvaging. You always want to replace both at the same time. If you don't you will always be limping along at below maximum performance.

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Old 09-05-2012, 04:14 PM   #24
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My battery distributor stated the AGM last 1.5 times as long for twice the money. I went with two group 29 lead acid batts and shoehorned them in.
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Old 09-05-2012, 05:09 PM   #25
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My battery distributor stated the AGM last 1.5 times as long for twice the money. I went with two group 29 lead acid batts and shoehorned them in.
Where are your batteries? I would have thought they were the same as ours. Ours are in compartments in the front of the trailer. One on either side of the A frame. As it is I can just barely get the group 27 AGMs through the opening.

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Old 09-05-2012, 05:18 PM   #26
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Same, same. The 29s Just barely fit and you have to be very careful when removing them that the positive post doesn't contact the tang for the lock latch. They don't sit all the way in...by that I mean that the end sits up on the door frame. I put a sheet cut from milk jugs to protect the case and hel in sliding it in and out. Told ya it was shoehorned in...but it has worked fine for 2 years now.

Someone on here had cut away the door frame a bit, so their batts would sit flat on the floor, but I haven't seen a need to do that. At least, not yet. If you pack carefully, there's still plenty of room for the cables and the little 7 amp charge controller for my 15 watt trickle solar panel in there too. The length and height are the concerns, not width. I also have fitted nylon straps around the case to assist in getting them out, as there's not much room for hands in there.

BTW, They're Interstates...the only group 29s I could find. No way 31s would fit.
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Old 09-05-2012, 05:37 PM   #27
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Whether agm or wet cell, remember to get deep cycle batteries. Automotive batteries are designed to deliver lots of current (to start the car) but not to be discharged very much. They will fail relatively quickly if fully discharged a few times. I use Trojan golf cart batteries in my ambassador. They are rated for 300 complete cycles. I have two big 6v batteries hooked up in series on a custom battery tray. Call your local golf cart dealer to get some good info on batteries.
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Old 09-05-2012, 05:44 PM   #28
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If the batteries are sitting on the frame of the box, doesn't that stress the top of the batteries since all their considerable weight is resting on the top of the battery? I cut down the lip and it was not fun, but my batteries sit on the bottom of the battery box. I don't look forward to removing them, but they came with straps attached, so I just have to work them out carefully with the strap.

Another way to go is with 2 golf cart batteries, but I would have had to raise the battery box lid and I didn't feel I wanted to do that nor did I need more than Group 27.

How long AGM's last compared with wet cells has been a point of disagreement. Lewster, who has a lot of knowledge about this, says 2 times as long. That equals twice as much cost and means I don't have to change batteries as often. AGM's are supposed to work better with solar too.

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