Heading out monday morning for a week of backcountry dry camping in my 25 ft TT. Just bought 2 brand new RV batteries, and are charging now (through camper inverter). Would a direct hookup to a battery charger do better? I plan to just run water pump as needed, a light or 2 maybe 1 hour a night, and considering running the gas furnace. What kind of drain will this be on my 2 batteries? What watt solar panel do I need to recharge them during the day? 5 Watt? 15 Watt?
Thanks in advance
Sounds like you might be ready to "take the plunge" into solar?..If that's the case please read this first as it could save you a lot of grief and money and will point you in the right direction.
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The "rule of thumb" for charging with solar panels is a minimum of 60 watts per 100 amp-hours of capacity. The upper limit for charging only would be 130 watts per 100 amp-hours (though there are reasons to go higher).
Do the new batteries correctly balanced wiring? This is very important if they are 12 volt units. Have a look here:
As for charging with a converter--it depends on what type is installed. The most modern three stage converter's will do an excellent job. It may take up to 39 hours to fully charge your house batteries.
I have documented how I upgraded my electrical system adding solar here:
And click on "Solar Boondocking", as well as "How to 'size' a Solar system"
Running the fan in the gas furnace may draw 4 to 8 amps. Of course it doesn't run 24/7 so the amount of energy used depends on how cold it is outside, whether there is a wind, and how high the thermostat is set.
randy grider wrote: Heading out monday morning for a week of backcountry dry camping in my 25 ft TT. Just bought 2 brand new RV batteries, and are charging now (through camper inverter). Would a direct hookup to a battery charger do better? I plan to just run water pump as needed, a light or 2 maybe 1 hour a night, and considering running the gas furnace. What kind of drain will this be on my 2 batteries? What watt solar panel do I need to recharge them during the day? 5 Watt? 15 Watt?
Thanks in advance
Regards, Don
Kustom Koach Class C 28'5" 256 watts solar, 875 amp hours in two battery banks 12 volt batteries 2500 watt inverter.
Can't answer your question about converter/inverter charging vs an external battery charger because you did not say what size if each you are comparing. My PD9160 converter will pump out 50 amps of charging current.
As to solar a 5 watt panel would not even make up for parasitic losses. I think you are looking at something like 60 watts to do what you want but the amount that you run the heater is a big factor. A forced air heater will draw something like 8 amps.
Thanks for the input, very helpfull ! Check out this link, and give you're opinions. I'm not a big Chicago Electric fan, but the price is tempting. How much could go wrong with something as simple as a solar panel charger? http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=90599
I do not know anything about those panels specifically but I am not a big fan of Harbor Freight solar products. If you look at those panels you will see that they have a uniform black surface, indicating they are amorphous types. Those have a lower efficiency and a shorter life than the polycrystalline panels. The polycrystalline panels are more expensive but IMO are a better value. I suggest shopping around and talking to some reputable solar dealers before you decide.
I find that my furnace is about 8 amps per hour, and I am guessing that you have group 27 batteries with 105 amp hours each? That gives you only 100 amp hours if you plan on discharging them to 50% before recharging.
My RV uses about 30 amp hours per day to run just the refrigerator, propane and carbon monoxide leak detectors. Then lights and furnace on top of that will require at least a single 120 watt solar panel to keep the batteries near full each day. But to recharge them, use the furnace, and some lights, then you will either need a generator or a couple more solar panels.
I get about 35 amp hours out of my 120 watt solar panels each day. I guess if I tilted them, I would get a little more power, but I don't want to climb on the roof more than required.
So I have a total of 400 watts of solar, and this keeps the batteries full no matter how much I run the inverter and TV set. I use a couple of florescent lights - dining table is 26W and sink is 8W that will really light up the whole living room by itself.
I have a Olympic Catalytic Heater that has a leg kit to make it portable with a dust cover to keep it clean. Now it is about 20 years old, and still going good. It uses no electricity at all, and puts out a warm heat all night long. Below 20, I tend to run the furnace a little bit to send heat into the corners, but normally the cat heater is doing fine on it's own.
If you are interested, here are a couple of sites.
I bought my first system from Rv Solar Electric. They offer lots of online sizing service, and the other place offered a great price on the 120 watt panels that I added to my original system. You can get the Olympic heater at RV solar electric. I have the 6,000 Btu and it heats my 30' motorhome great when it is over 30 by itself. I would not recommend a larger one.
Before you jump get some prices. Solar is great but expensive. I have 3 100w Panels, 6 Interstate U2200 Battery's also a Prosine 2.0 Inverter. Took me just under 2 years to afford to have it all installed. I would recommend you look here.
They still know the meaning of the words customer service.
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