Very basic question

[Weavery]

My mind goes into brain freeze thinking about electronics so please forgive this dumb question, you have been very kind with help in the past.

I have never boondocked. I have a reservation in a National Park for a weekend in August. I have a 2002 19' Scamp. All my lights are LED. I expect to use lights, the exhaust fan and occasionally the water pump. I do have an electric motor on the front legs if I disconnect from the truck. I would like to take a solar battery charger. I saw this one on ebay: Coleman 40W 12 Volt Folding Solar Panel Kit with Stand + 7.5 Amp charge controller. Will this do the job? Can I hook it to the battery while it is connected to the trailer? Any better suggestions? I will be in a mostly shaded spot and wanted something I could move around. Does adding a long cable reduce efficiency?
Thank you in advance!
Jean

Sent from my SM-N920V using Fiberglass RV mobile app

[Warren Wilson]

There will be complex and complete responses, no doubt. Your best bet will to do the calculations. I have only a little anecdotal information for you from the perspective of a guy in a 17' Boler.

I bought an inexpensive panel and controller and only clipped it onto my battery when the tow vehicle was disconnected. With LED lights, a water pump and a small furnace fan running I never ran out of power, camping off grid several days at a time -- probably never more than three days between drives (when the tow vehicle charged the battery).

(Of course I also take a small generator along just in case, but I have never actually needed it).

[David B.]

Jean, without know the capacity or group number of your battery, that would be a difficult question to answer. Unless you are going to add into the mix some TV watching, CPAP machine, and recharging a laptop computer, you should be fine for the weekend without additional power. A 40 watt solar unit like you described should be adequate to keep your battery/batteries topped off, but not necessary. You could always "dry camp" in your driveway for a couple of days to do a trial run.
Dave & Paula

[Glenn Baglo]

Sounds like my set-up. I started with one Coleman 40 watt panel and added a second one just because it was on sale. I have a hub so the two panels connect to the hub and the hub to the 7.5 amp controller and the controller ( with alligator clips ) to the battery terminals ( a Group 27 battery ). Battery remains connected to trailer. So, I have a spare 7.5 amp controller that I don't use.
I unplug from the tow vehicle as I did drain the tow battery once.
I also have a Honda 1,000 watt generator that I leave at home now.
Trailer is all LEDs. Propane furnace takes the most power to run ( the blower ). Fridge is propane and uses a little 12V for the controls. Have a Maxxfan that I don't use all that much. Use water pump. Charge my laptop, an iPad, Bluetooth speaker, iPhones. No TV, but run a Sirius satellite radio and dock.

You don't say the price on Ebay, but I got mine at Canadian Tire for $99 ( CAD ) each on sale. They go on sale regularly for that price.

[Gerry]

As Dave said, If your frugal with your power usage you can get away with the set up but you would probably have to make sure you panels are in direct sunshine for as long as the days is. If you run into 2 days of clouds your in trouble so better have a generator.
I spent the season on a sunny site working in the National Forest with a 30 watt panel and 2 group 27 batteries for my 1979 Boler 1300
Charged #1 unhooked battery making sure it stayed in direct sun all day.
Hooked #1 battery in the PM so had plenty of power for LED lights and furnace to run if needed. Ran fridge off propane.
Next day Charged #2 battery and babysat the solar panels again. in the PM Hooked up #2 and repeat cycle all summer long.
Had a Honda 1000 watt generator and used it when we had a week of rain,

[floyd]

From what you have described, you should be fine.
We have gone several days using the shower, lights,Fantastic Fan, television, etc. with only a group 27 Battery. (and that was before we switched to LEDs)

If you take along a good pair of jumper cables and it becomes necessary, you could always charge your battery at idle from your tow vehicle for about 20 minutes to top it off after a day or two.

[sokhapkin]

20 minutes to recharge a battery? I'm in doubt... Maybe you mean 2-3 hours?

[C&G in FL]

Originally Posted by sokhapkin

20 minutes to recharge a battery? I'm in doubt... Maybe you mean 2-3 hours?

I'm not sure Floyd meant completely charging the battery. I think he meant 20 minutes on jumper cables would allow the vehicle's alternator to recharge the battery enough to keep it performing adequately, without dropping to critically low voltages.

[floyd]

Originally Posted by sokhapkin

20 minutes to recharge a battery? I'm in doubt... Maybe you mean 2-3 hours?

No, I meant what I said.
We are talking about taking a deep cycle battery from the high elevens or 12.0 Volts, back to 12.7 Volts using a good pair of jumper cables directly attached between the RV battery and the tow vehicle battery with the tow vehicle running. The surface charge might actually reach into the low 13s.
(Thanks CPW)

[Mike Magee]

You should be ok. I used a 70W during a week of dry camping, running the same items you mention, and had no problems. I did switch my lights to LEDs though, because they use 1/5 to 1/10 the current of incandescents.

A long wire from panel to controller isn't too bad, but a long run from controller to battery is not so good. I don't know how the set you're looking at is configured.

[Mary F]

We used a similar setup for several days at a time in our 1998 Casita. Our lights at that time weren't LED, and we only turned them on when needed, such as for working in the kitchen. We also took along a fluorescent lantern (battery powered) for ambient (not reading) light. That exhaust fan might use more power than your lights, unless it's a Fantastic or MaxxAir fan. (By exhaust fan, I'm thinking of the one in the power hood over the stove.) But, having said that, we sometimes used our furnace (with its power-hogging fan) to take the edge off a mountain summer morning (45ºF). My info's all anecdotal, but is why I think you will be okay. I assume your refrigerator will run on propane, and is NOT one of the fancy ones with electronic controls, so you're not concerned with another, probably small power drain to your system. Have fun!

[Wayne Collins]

Your refrigerator can be the largest load on the battery. If you have a volt meter, with the truck disconnected, check the voltage at the 12V terminals at the back of the fridge -with fride on and off.. It should be at least 11 volts. If it goes down to 10V, it shows that there is too much resistance in the wiring.
Our 2000 16 ft Scamp was wired so the fridge wiring went through the fuse box/inverter. the size of wiring was a bit light. I ran a 12 gauge wire directly from the battery to the fridge - with an inline fuse - to have low resistace path.
Or, you can leave the fridge off and use Ice Chests.

[floyd]

Originally Posted by Wayne Collins

Your refrigerator can be the largest load on the battery. If you have a volt meter, with the truck disconnected, check the voltage at the 12V terminals at the back of the fridge -with fride on and off.. It should be at least 11 volts. If it goes down to 10V, it shows that there is too much resistance in the wiring.
Our 2000 16 ft Scamp was wired so the fridge wiring went through the fuse box/inverter. the size of wiring was a bit light. I ran a 12 gauge wire directly from the battery to the fridge - with an inline fuse - to have low resistace path.
Or, you can leave the fridge off and use Ice Chests.

Salient point being... Don't use the fridge on 12V, especially when boondocking. We don't bother with it even when charging from the TV while in transit.

[Huck]

If it was me, I would spend the extra money and get 100 watts.

[Wayne Collins]

Originally Posted by floyd

Salient point being... Don't use the fridge on 12V, especially when boondocking. We don't bother with it even when charging from the TV while in transit.

Ah yes, Floyd:
We should use the LP gas when dry camping. We did always run on 12v while on the road. but tried to remember to turn it off at lunch stops or longer.
Otherwise it would run down the TV's battery. /WC

[HawkBoler72]

My Boler 1300 is equiped with all lights in LED, four 12x12 cm computer fans as vent fan, four 10x10 cm blow fans as exhaust fan, one 24 group AGM deep cycle battery. A 0.8 AMP doom fridge uses grid power at camp site and uses the battery when on road (with a 1000 W pure sine wave inverter). I don't want to use my TV (Sienna van) to maintain the AGM battery, so I connect a 40 W solar panel to the AGM battery when moving.

[gordon2]

Originally Posted by Wayne Collins

Your refrigerator can be the largest load on the battery....

Only if running the heater (to cool the fridge) on 12 VDC. OP will not have any luck doing that and knows so. Some fridges do require 12 VDC for the electronics but mine does not. Those that do, do not use much power at all but will not work when the voltage drops too far.

Originally Posted by Mary F

..That exhaust fan might use more power than your lights, unless it's a Fantastic or MaxxAir fan...

There is no magic in the Fantastic Fan Samp uses (and I assume the MaxxAir fans also). In practice, fans are often the biggest power hog in a camper and one brand is not much more or less efficient than another brand.

The OP did say they have LED lights. I have all LED lights in my Scamp and with them ALL on, the load is about one amp. The Fantastic Fan alone, on high, draws 2.4 amps.

The 40 watt panel when it is in direct sun will replace about as much as the fan uses (on high), so thats a wash. But of course you won't have perfect conditions. If you only use the fan for a few hours and not on high, and also go easy on the water pump, and lights are not on all night, you could get by for an extended time in good summer sun with a 40 watt panel. In a shady spot, under clouds, etc. - not so much. In that case you will be more limited to the capacity of the battery (much like not having solar at all). In any case, a few days should pose no problem but a large panel might be called for, and/or a larger or more battery if you have extended times without enough sun.

But also be on the lookout for so-called "phantom" loads such as a propane detector. That can draw you battery down in a week or two without you knowing why.

[Mike_L]

i boondock from 40 to 60 days per year. I'm always off the grid. I use solar all the time. I have a 2500 watt generator which I only use for winter camping. A 40W Coleman solar panel will provide 2.3 amps of DC power maximum in direct sunlight. You can use alligator clips to hook it directly to your battery and leave it there when you are parked. This panel has a back flow preventer so it won't kill your battery when the sun goes down. Longer wires have more resistance so I use a heavier gauge to compensate for this.
You should be good if you manage your power consumption and try to keep your solar panel oriented towards the sun all day long. This means you may have to move it during the day.
Anything with a motor (fan etc.) uses a lot of power. Your carbon monoxide and flammable gas monitors run 24 x 7. LEDs use 1/10 the power of conventional bulbs. The manufacturer will list the power consumption of all these things. Multiply these numbers by your hours of use and you have your power consumption. Divide the output of your solar panel by 2 to account for lower light conditions and multiply by your hours of sun exposure to calculate power generation. Generation should exceed consumption.
I used 40W for years and did fine. I opted for 3 of these panels so I didn't have to reorient them during the day and now I have more than enough power. Cheers!

[steve dunham]

Originally Posted by Wayne Collins

Your refrigerator can be the largest load on the battery. If you have a volt meter, with the truck disconnected, check the voltage at the 12V terminals at the back of the fridge -with fride on and off.. It should be at least 11 volts. If it goes down to 10V, it shows that there is too much resistance in the wiring.
Our 2000 16 ft Scamp was wired so the fridge wiring went through the fuse box/inverter. the size of wiring was a bit light. I ran a 12 gauge wire directly from the battery to the fridge - with an inline fuse - to have low resistace path.
Or, you can leave the fridge off and use Ice Chests.

Or you can run the refrigerator on propane. Our experience is similar to Floyd's . We can go 2 or 3 days on our one 27F deep cycle battery if we practice a little conservation and we only run our furnace for a short period in the morning . We don't carry a bunch of electronic equipment that need constant recharging when we camp and have LED lamps. In the summer we get up and go to bed with the sun and if we do need light after dark , we light a campfire.

[Mike Magee]

Be aware that you want to keep your battery above 1/2 charge whenever possible, for longest battery life. If the battery dips below about 12.1V, it's below 1/2. Severe depletion causes sulfation. So a little extra solar charge capacity is better than being a little short.