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Old 09-10-2011, 11:27 AM   #31
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So, 27 amps a day will require a battery that has at least 54Ah, which is basically any group 24 or larger. But that group 24 battery will be at 50% after 24 hours (The life of the battery is shortened dramatically by depleting below 50% too often).

Also, the cold temps you intend to camp in at this time will reduce the battery capacity. Temps of 40-50 degrees reduce the cap by about 20%.

So it seems that you will need a battery with a minimum of 70AH to last one day at your daily requirement.
Scott,

I am curious as to how you arrived at the 54AH number for a load of 27 amps? What was your reasoning as I am having a hard time coming up with your figure.

At 1 amp draw, a 54AH battery will deliver that 1 amp for 54 hours (thus the 54AH rating). Assuming a flat discharge curve (which it is not), a 27 amp load will kill a 54AH battery in 2 hours. Since the discharge curve is not flat, the most you will get at 27Amps is about 54 minutes (reduced 100% capacity estimate of 30AH).

Otherwise your logic is right on.
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Old 09-10-2011, 11:31 AM   #32
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Scott,

I am curious as to how you arrived at the 54AH number for a load of 27 amps? What was your reasoning as I am having a hard time coming up with your figure.

At 1 amp draw, a 54AH battery will deliver that 1 amp for 54 hours (thus the 54AH rating). Assuming a flat discharge curve (which it is not), a 27 amp load will kill a 54AH battery in 2 hours. Since the discharge curve is not flat, the most you will get at 27Amps is about 54 minutes (reduced 100% capacity estimate of 30AH).
I took his 27 amps as being the load for the entire day.
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Old 09-10-2011, 11:36 AM   #33
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One single 921 bulb left on all day is over 24 amps.
A two bulb fixture left on for 24 hours draws almost 50 amps.
The 200 milliamp Propane detector is 4.55 amps a day.
I think 27 amps a day is wildly low.
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Old 09-10-2011, 11:57 AM   #34
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I know what you're saying but it can be done.

We mostly dry camp in our hybrid and my minimum daily requirement seems to be about 34 amp-hr when camping with the family. I calculated that on one 4-day trip this July and it was confirmed when my 260Ah bank was at 12.0 volts or 45% at the end (oops).

I'm lower when I've taken out the trailer on my own.
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Old 09-10-2011, 12:45 PM   #35
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How many hours a day did you run your furnace in July?
4?
I think not.

45% of 260AH is 117AH

My 150AH set would be flatter than my Aunt Tillie.

A 54AH battery would be... Oh, wait...

Seriously, your setup is what is needed for the camping you do. For a weekend, 150AH would be the minimum I would consider.
Winter camping I am back to 230 Plus bank.
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Old 09-10-2011, 02:40 PM   #36
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As mentioned above, the 27 Amps/day came from someone spreadsheet who recorded current draws for each appliance/fixture of his Roo using his TriMetric.

Reading the above converstation, I'm leaning toward purchasing a Mr. Heater and a touch more battery capacity "just-n-case". The heater I can use elsewhere, but a "significant" battery upgrade can only be used in the RV.

The cheap-o Group 24 that came with the camper is brand new (less than a month), so I'm thinking I go buy (though I need to check the price) another of the same and wire them up in parallel (and add a on/off switch in the process).

That appears to be a simple cost-effective approach that should meet my needs and not any additional complexity to my camping experience. Gadgets are cool and I can certainly relate, but I've learned that simple is sometimes just eaiser and less stressful.
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Old 09-10-2011, 03:03 PM   #37
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BIA,

Yes, the Full Monty is not every one's cup of tea for sure.
Whatever you decide, use great care with the Mr. Heater.
Ventilation is critical as your don't want to wake up dead.
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Old 09-10-2011, 07:04 PM   #38
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Ventilation is critical as your don't want to wake up dead.
That would be somewhat very, very difficult:
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Old 09-10-2011, 08:26 PM   #39
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That would be somewhat very, very difficult:
Zombies!
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Old 09-12-2011, 10:46 AM   #40
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Reading the above converstation, I'm leaning toward purchasing a Mr. Heater and a touch more battery capacity "just-n-case". The heater I can use elsewhere, but a "significant" battery upgrade can only be used in the RV.

The cheap-o Group 24 that came with the camper is brand new (less than a month), so I'm thinking I go buy (though I need to check the price) another of the same and wire them up in parallel (and add a on/off switch in the process).

That appears to be a simple cost-effective approach that should meet my needs and not any additional complexity to my camping experience. Gadgets are cool and I can certainly relate, but I've learned that simple is sometimes just easier and less stressful.
Everyone has been so helpful I really appreciate it. Now i have a pricing question...

I just called the RV dealer where I purchased the Roo. A new "basic" Group 24 battery runs $77 (plus tax) and an additional battery box is $12. I assume I can find a local source for the additional lengths of wire to connect the two in parallel.

For roughly the same amount could I higher capacity Group 27 or 31? Ex. if $100 gets me a single high (enough, see above thread) capacity Group ZZ battery, I'd ditch the cheap-o 24 that came with it.

Thoughts?
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