I have a 2007 Roadtrek 170. In mid-June I needed a new house battery just before a trip. Neither of the 2 local RV places could give me an appointment in time so I was referred to a Battery Systems business. They put in a Centennial DC27MF (maintenance free which I think means it was an AGM battery). Everything seemed fine for my short-term and longer trip in June (both dry camping).
However my recent 12 day camping trip to eastern Sierras was a different story. Soon into the trip I noticed that the battery was dead by morning and I had to turn on van engine in order to charge enough to get generator going. I am pretty consistent (but not perfect) in turning off water pump...the only thing that was on most of the night was the vent fan (though that hasn't been a big drainer in the past). By the end of the trip I was running the generator 3 times a day to keep a charge. I now see what you mean by AGM having less capacity........but does this sound like a capacity problem or bad battery/charging problem? I think I want Battery Systems to take this battery back and refund at least part of my money back, and then I'd like the RV place to put in a battery like the previous ones I've had. But should I have them replace this AGM first and see what happens? Not sure they have non-AGM batteries.
A maintenance free battery is not necessarily an AGM. Many wet cell batteries are built with sealed caps that can't be opened to add water. They call them maintenance free. What you really have is a type of battery that needs water added from time to time but no way to do it and a name that I guess makes people feel okay about that.
For a car starting battery this may work okay. I suspect that's what you have, a car starting battery. A deep cycle wet cell with caps that allow you to add water when necessary would make a lot more sense.
Not all maintenance free batteries are AGM. A group 27 has only about 85 amp-hours of capacity and only 50% of that should be used. Taking it to "dead" is a quite route to destruction of the battery. Each deep cycle discharge causes permanent partial capacity loss.
What you saw is called progressive capacity loss. It comes from not recharging to 100% state of charge between drawing down the battery.
If boondocking for 12 days much greater capacity and/or a solar system would be a wise investment.
Rodger, So maybe I wasn't running the generator long enough to fully charge the battery once it went all the way down (didn't have enough juice to start generator). Though once the charging light went off, the battery level did read "good"...but it wouldn't stay there very long. (I was dry camping.)
What should I do about this battery? Replace it with another the same, or get refund and then go to RV place and get one like I had before? That's the central question here....
* This post was
edited 08/05/12 09:06pm by mmckell *
Start with an energy audit. Once you know how much power you use in 24 hours, multiply it by twice the greatest number of days you wish to boondock. That will size the battery bank correctly for you.
I get great service out of so called marine deep cycle batteries. The secret is having a way to recharge efficiently and cheaply. That can be done several ways. Shore power, solar power, or generator power. With panels as low as $0.82 cents per watt solar is the nearest thing to a free lunch you are likely to find.
Sounds like your main problems were drawing the battery down too far, and not coming anywhere near a full recharge before drawing it down again. You may want to look at a larger & faster charger, and a true deep cycle battery. For now, be aware that driving the van will charge the battery must faster than the stock charger, maybe 4 to 6 times as fast. I think the RT owner's manual has a brief section on this; my '02 C190P's did. Just running the engine at idle probably won't do it.
You also should add at least a digital voltmeter. The lights on the indicator panel are pretty useless or even downright misleading. Camping Wirl'd sells a cheap one that goes into a lighter socket. Use it on a house circuit, not the dash.
I seriously doubt there's enough room in a 170 to install a 'battery bank'.
Jim, "Blessed is the end user who expects nothing, for he shall not be disappointed."
'06 Tiger CX 'C Minus' on a Silverado 2500HD 4x4, 8.1 & Allison (aka 'Loafer's Glory') www.tigervehicles.com