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Old 02-06-2006, 05:36 PM   #1
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1991 25' Excella
SF Bay Area , California
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Question battery power

Does anyone know how long you can run on battery power? We have a 1991 25' Excella for which we just bought a new battery. How long should we expect to be able to run on battery, such as overnight when running the heat? Do any of you run two batteries at a time? This is probably a dumb question... do two batteries double the voltage or increase the running time available? How does that work? Thanks for the help.

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Old 02-06-2006, 05:41 PM   #2
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1974 31' Sovereign
1993 21' Sovereign
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Two batteries in parallel will double the amperage, while maintaining thbe voltage. Two batteries in series will double the voltage, while maintaining the amperage. Parallel is connecting batteries + to+, and - to -. Series is connecting batteries + of the first to - on the second, then + on the second to the power feed on your coach. This can only work if you install two 6 volt batteries, as two 12 volts batteries will damage nearly everything in the electrical system of the coach.

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Old 02-06-2006, 08:59 PM   #3
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You should be able to run at least three days and two nights in mild to cool weather (occasional furnace use) on the batteries in your rig. There may be an adjustment process of either adding battery or adjusting lifestyle to meet this goal, though. Some, I think most, folks can go quite a bit longer, especially if not needing the furnace as much.

The energy capacity is mostly determined by weight and size of all of your batteries together. Parallel vs serial is a religious argument for some but the difference is in the noise as far as practical matters go (except for making sure the wiring is right).

Properly installed batteries need a ventilated cabinet that will contain spills in order to meet code. Even AGM's are supposed to have this (for code) but don't really need it.
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Old 02-07-2006, 01:57 PM   #4
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Originally Posted by aeriqua
Does anyone know how long you can run on battery power?
A discussion of this is at
Nick Crowhurst, Excella 25 1988, Dodge Ram 2500 Cummins Diesel. England in summer, USA in winter.
"The price of freedom is eternal maintenance."
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Old 02-08-2006, 09:11 PM   #5
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How large is your battery? Size 24 or 27?

Amp hours are the key and you want more of them. I discussed this issue at length in the current issue of Airstream Life (Winter 2006). Do you have a way to recharge your battery? (aside from your tow vehicle?)
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Old 02-08-2006, 10:12 PM   #6
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2004 25' Safari
. , Illinois
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With two batts, using the furnace at night, stereo, pump, lights and fantastic fans during the day, I got about 6 or 7 full days....I would think with similar use, you'd get half that with one battery.
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Old 02-09-2006, 01:04 AM   #7
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How long you can run infers full battery/ies, no recharge and use to complete discharge. Lots of factors influence the time. An important one to remember is that the healthy life of the battery is markedly reduced by very deep discharge events. As a guide recharge when 50% discharged. Say you begin with 80A or 105A, divide by 2, get your manual out and see what the appliances you're using draw (per hour). Except for phantom loads and the refer, the draw is intermittant so use likely fractions to multiply your amps for each. The stingier you are the longer it takes to use up 50% of your amps...or completely discharge and replace your battery/ies sooner
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Old 02-09-2006, 07:33 AM   #8
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1989 34' Excella
Johnsburg , Illinois
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Biggest load

How long you can go depends on where you are in the country, how cold and blowy is it and how good your batteries are. If you want maximum time, buy the deep cycle batteries. Be aware they usually come with a shorter warrentee period because they know people abuse them and they do not want to pay for your abuse. Even with deep cycles the previous poster was right in suggesting you never draw them down to less than 50%. Another approach is to abuse Walmart by buying automotive batteries and getting a free replacement before the full warrentee period expires. (They test them to make sure they are defective before they give you a new one so sometimes this does not work.) Up North the furnace fan is the biggest amp hour draw on the battery system and that is usually the controlling factor. Putting LED lighting will save you a bit but may not be worth it unless your bonedock alot.
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Old 02-09-2006, 10:22 AM   #9
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The State of , Ohio
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This web site should answer your basic questions about batteries.

Make sure to continue on to Part II.

The 12volt Side of Life
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Old 02-09-2006, 10:46 AM   #10
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1991 25' Excella
SF Bay Area , California
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Thank you all so much for the great responses and info. My "to do" list has just grown HUGE. I'm off to check into size 27 AGMs, see how many amps by battery has now, get a 2000 generator, and on.... Thanks for all the help. You all are a great resource.

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