I know, more battery questions!! - Fiberglass RV


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Old 05-01-2003, 10:59 AM   #1
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I know, more battery questions!!

Okay, I am still struggling with this battery issue after one full year of Casita 17' FD ownership. On our last 3 day outing, being very conservative, our 3rd day became iffy. I know we could not have spent an extra day because we were down to approx. 11.0 volts on the battery (maybe good?). I know there is the option of increasing the battery size, or adding another battery, but I am still curious why I cannot get a full 3 days of camping in on the existing Group 24 battery? Our refrig is on gas, we run our lights sparingly, etc.
Please Help!!
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Old 05-01-2003, 12:48 PM   #2
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A real quick search on the internet found this table for batteries at a spring-like temperature:

Temperature: 57 degrees Fahrenheit
Percent Hydrometer Unloaded
charge reading voltage
100 1.258 12.59
75 1.203 12.26
50 1.153 11.96
25 1.113 11.72
0 1.093 11.60

Group 24 lead-acid batteries have, I'd estimate, 60-80 amp hours in 'em. For long term battery life, deep cycles really shouldn't be discharged more than 50%.

Here are some measured loads from my Casita:
Interior lamps: 1.5 amps per hour per light.
Water pump: 7.0 amps per hour.
Fantastic fan on low: 1.8 amps per hour
Stove fan: 1.3 amps per hour
Bathroom fan: 1.5 amps per hour

You live in California. I'll SWAG this sort of daily usage. Feel free to adjust to your estimates.

2 lamps on for 3 hours = 6 amp-hours (Stock 18 watt bulbs, 8 pm to 11)
water pump on for 15 min = 1.75 amp-hours (cycles on and off every time you turn on the faucet. I'm ignoring the startup loads)
Cabin fan on for 4 hours = 7.2 amp-hours (just during the warm part of the afternoon)
Bathroom fan on for 20 minutes = 0.5 amp-hours (Hmmm. It is the throne room after all. Read an article in Field&Stream, contemplate life's mysteries, etc)
Stove fan on for 1 hour=1.3 amp-hours (Breakfast and supper)
Total=16.75 amp-hours per day

For three days it equals 50.25 amp-hours. DUDE! That battery's way over extended!
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Old 05-01-2003, 02:01 PM   #3
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I know, more battery questions!!

Well, maybe it is my battery that's low! That does sound about right. Another question is, I noticed you have a 16' Casita, what have you done to overcome this?
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Old 05-01-2003, 02:25 PM   #4
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battery drain

Paul:

Not uncommon, but agrivating.

Perhaps your battery has a weak cell???

IMHO, a 24 isn't enough for 'average' use. With lights, fans, tv, etc..

=====

If your 11 volt reading was with a volt meter, the battery should be in cardiac arrest. All the info I 've read states 12.5v is 'minimum'. A fully charged healthy battery under no load should be over 13v.
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Old 05-01-2003, 02:31 PM   #5
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Quote:
Orginally posted by Paul Bacchi

Well, maybe it is my battery that's low! That does sound about right. Another question is, I noticed you have a 16' Casita, what have you done to overcome this?
Paul,

If you changed to a group 31 battery, you'd still run low after maybe 4 days. If you add a 75 watt solar panel, you'll never run low. Your limit then will be the black water tank. Ours had the 17 gallon tank and we could run 5 days (6 with conservation measures) before dumping. With the solar panel, we just never worried about the battery.

Another alternative is a small generator. Get a quiet one or your neighbors will hate you.

Use the Search function to search for "solar" and "generator." There is a wealth of information on the forum.

If you're running down to 11.0 volts, you're overdischarging the battery. That will seriously shorten its life.
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Old 05-01-2003, 03:08 PM   #6
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Paul ... my wife and I are spending more than 6 weeks in Colorado, mostly at three mountain-top, no-service campgrounds from late May to mid-July this year ... we can get three days (or longer) out of a Jump-It emergency battery ... and can leave most 10 day dry camps with a fully-charged house battery. (We space out 10 or 12 day dry camps with a couple days of commericial electric/water to recharge/do laundry/get groceries, etc.)

In fact, we try to save most of our Jump-It battery power for an occasional furnace cycle (first thing in the morning, getting ready for bed at night), to take the edge off the trailer.

Takes a lot of practice ... but briefly, here's how we do it.

1. Flush toilet with a gallon jug of water, instead of running pump to pull water from fresh water tank. No need to use the whole gallon of water ... in fact, flushing with a jug gives you more control over how fast your black tank fills up.

2. Use solar candle, various stand-alone L.E.D. and fluorescent lights inside the trailer at night, instead of running the trailer's house lights.

3. Do most of your cooking and dish washing outside the trailer, using water heated over a campfire or propane stove, instead of running stove exhaust vent and water pump, pulling hot water into sink. I even dart out in the morning to fire up some hot water over a fire or campstove for morning coffee and tea.

4. Use a solar/crank am/fm radio/flashlight for tunes and news instead of running tv or radio off trailer battery ... although we love to be in spots were you can't receive tv/radio/cell or even national weather service broadcasts. If you get good reception, you're camping too close to civilization!

5. Use a Coleman Black Cat to take edge off trailer, during a daytime cold snap or shower (spacing out in-trailer showers with dips in nearby hot springs or bucket "military-style" showers).

Now, rain and even an occasional summer mountain-top snow-storms can alter the best-laid plan, and cause you to use more power (which is why I carry a number of Jump-It's).

But if you think ahead, and think of ways to NOT use the power of your trailer battery, you'll be able to extend your dry camping almost indefinately.

I know, I know, some of you are saying, "wait a minute ... why should I have to act like I'm camping in a tent when I'm in a fancy trailer."

Well, if you are going to spend six weeks in the mountains, dry camping, far away from society ... which by the way, is just an absolutely wonderful way to get one-on-one close with your spouse ... you need to alter your thinking a bit.
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Old 05-01-2003, 03:10 PM   #7
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Quote:
Orginally posted by Paul Bacchi
I noticed you have a 16' Casita, what have you done to overcome this?
:lol Oh!! your talking battery :yep :crazy-ii
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Old 05-01-2003, 05:02 PM   #8
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Ummm. I wondered about that briefly. You can call me ugly, but don't be slammin' my trailer!! Like they said in the Ole West, "Smile when you say that, Pardner!" ;)

I'm guessing it didn't come out quite the way he intended.:o

The newer Casitas have a group 27 battery, but they're only 85 to 105 amp-hours. Only adds a little more time. I haven't boondocked yet, but I've been giving it alot of thought as I considered loads that a solar panel would have to replace and what size panel I should get. Here in the upper midwest, I'm leaning towards a 50W (about 3 amps per hour). On sale for about $400 with a digital controller included seems like a pretty competitive price.

As an aside and as Don implies, this sort of points out the advantages of a digital voltmeter, or at least an expanded scale analog meter that allows you to read to 1/10ths of a volt. There's not much voltage difference between 50% discharged and dead to the world voltage.
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Old 07-02-2003, 05:49 AM   #9
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Second Battery

Paul, here is an idea that may work for you. I do not know what type of tow vehicle you use, but if there is room for a second battery in the engine compartment (or any place else), you can hook the second battery up to the vehicles charging system with a battery isolator between the charging system and the second battery. Then, tie your wire going to the trailer to the second battery. During the day, as you drive about, you will “top” off the second onboard battery, then, at night, plug the trailer into the vehicle. This will give you a second battery that is fully charged plus help recharge the trailer battery as the two try and equalize to each other. And since you have an isolator between the second onboard vehicle battery and the vehicle’s primary battery, you will not discharge the primary battery. Also, if you ever have a dead battery on the primary battery (vehicle will not start), get your jumper cables out and jump between the two batteries. Just do not forget to unplug from the trailer before you leave in the morning. By the way, we use a 70 watt solar charger which works great, but I am still trying to figure out a way of installing a second battery in the trailer (Casita 17’). I have come up with a couple of ideas and will share them when I decide which way I go. – John –

PS Steve’s power consumption figures are pretty much what I have come up with. We use a laptop (IBM Thinkpad 600) and with the 12V car adapter, it pulls about 2.3 amps. If we watch a DVD, I figure on about 22 amps consumption for the day.
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