Wayne in Tennessee
Louisville TN
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I have a 1990 Foretravel with 3 12volt 8D batteries. We are not full timers and when the coach is stored between trips it is not hooked up to shore power. The batteries will discharge after 2 to 3 weeks. I am thinking of installing a solar panel just to keep the batteries charged during storage. We live in East Tennessee, so it's not going to be sunny all the time. What size solar unit do I need?
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Golden_HVAC
Fulltime, CA, USA
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Joined: 08/19/2003
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Hi,
You have a pretty good size load on the set of batteries to discharge the 400 amp hours in only 4 weeks. You might be much better off using a battery disconnect post on the negative terminal, and loosen the screw that connects the input and output together when not camping.
As for the solar panel, I have a e-meter that monitors my amperage going into and out of the RV batteries. At night with no lights on, it is drawing about 1.2 amps to run the refrigerator, CO meter and propane leak detector. That works out to about 35 amp hours per day, or what one of my 120 watt solar panels puts out in a day.
You can find great prices on 24 volt panels here, they might also have 12 volt panels. You can also buy a 24 volt input solar controller with 12 volt output. There area also RV specific controllers with dual 12 volt outputs for both the engine and coach batteries, with priority on the coach battery until it is full then the engine battery.
SunElec.com
SOlarOnSale.com is where I bought my pair of 120 watt solar panels.
RvSolarElectric,com is where I bought my first pair of 45 watt solar panels.
Fred.
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pianotuna
Regina, SK, Canada
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Hi,
I'd suggest reviewing how the batteries are wired together. Since there are an odd number, method #3 on the url below is the only way to balance them properly.
correctly interconnecting multiple batteries
Assuming you have 675 amp-hours of storage the range of size for a solar system may be between 405 and 1013 watts.
Regards, Don
Kustom Koach Class C 28'5" 256 watts solar, 875 amp hours in two battery banks 12 volt batteries 2500 watt inverter.
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CA Traveler
The Western States
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Drive the rig to a good battery shop and have the batteries load tested. Forget an auto store for 8Ds. Next beg, borrow, buy or steal (not really) a DC clamp on ammeter and find out what the drain is when stored. A battery disconnect switch might be a good idea.
2009 Holiday Rambler 42 Scepter with ISL 400 Cummins
2004 Honda CR-V
Bob
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CA Traveler
The Western States
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Now that you know the drain a 200W flat mounted panel and PWM controller should be adequate to keep the batteries charged in storage.
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garym114
Bluff Dale, Texas
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To store you batteries without being connected to shore power you have to remove all loads. To do this you have to charge them fully, not just a couple of hours. Remove the ground cable from the battery bank, the one that goes back to the frame of the MH. Thia will remove all load and the batteries will keep just fine for several months, the colder the better.
2000 Sea Breeze F53 V10 - CR-V Toad
Some RV batteries live a long and useful life, some are murdered.
Get a Digital Multimeter and Learn How to Use It
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wa8yxm
Wherever I happen to park
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3 8Ds is what, about 700 amp hours.. Unless you have a bunch of stuff turned on discharging that fast indicates you have a problem.
Do you leave the inverter on? LIghts? What is left on inside the RV when stored.
Lift the negative cable off the batteries (the one that runs to the chassis, ignore cables that run only to other batteries) and see if this stops the discharge,, Should be able to go several months without a re-charge.
You are loosing over 100 amp hours a week, consider how much solar panel you will need to replace that.
Nothin adds excitment like something that is none of your business
Kenwood TS-2000 housed in a 2005 Damon Intruder 377
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n4hwl
Murfreesboro,TN
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With these 3 12 volt batteries in parallel you might consider this. I may be wrong but if you have one bad battery( bad cell ect.) then it will quickly drain or kill the other batteries. You might check all 3 batteries to see if you might have one bad one pulling the other 2 down. Is this not true? Someone let me know
Ken
2004 QDH 40ft Phaeton, Blue Ox Tru-Center
Ham Call N4HWL, TS performance mp-8
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pianotuna
Regina, SK, Canada
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Hi Ken,
Yes, one bad cell (as in shorted) will draw down the other two batteries, but it usually happens FAST.
* This post was
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edited 02/07/12 05:03pm by pianotuna *
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CA Traveler
The Western States
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An open cell would leave with the equivaent of 2 batteries. A shorted cell could have a significant impact on the life of the other 2 batteries. That's one reason why I suggested that you have the batteries load tested.
My rig has a switch for everything except the Magnum converter/inverter which draws 0.3A, ie it never shuts off. That alone means the batteries will be 50% discharged in 30 days. I'm still "thinking" about my options for a switch.
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