Batteries and Solar Panels

[slo-ryde]

I'll be a travel trailer owner soon and would like to know what types of battery/solar panel set-ups to look at. I prefer campsites that are off the beaten path but not quite boon-docking. These sites usually have no hook-ups for the trailer but do have hot showers/bathrooms and water faucets scattered throughout the campground. I don't do much camping during the hottest months of the year so the A/C isn't a concern for now. I do enjoy camping during the fall and winter so the furnace will be needed. A generator is a possibility but I'd rather go with a solar system sized to keep me comfortable. I just don't care for the noise and hassle of carrying along a generator set and fuel for it. I will have the option of charging the trailer battery from the truck with the engine running but that would only be a last resort option due to the noise and amount of time the engine would have to be running.



The only things I would be using in the trailer would be:

1. refrigerator

2. furnace

3. lights

4. tv, radio, and laptop (using small inverter)

5. stove

6. fans

7. hot water heater (sparingly)

8. leak detector



I've been looking a batteries and found a battery from Interstate with an RC rating of 390 minutes. If I understand the terminology that means the battery will run a 25 amp load for 6. 5 hours!? It weighs 120 pounds but will actually fit in the factory battery tray. I would probably discharge the battery to around 80% during the day at the most. Camping World has a 75 watt panel for $350 installed. Does this sound like enough solar panel to charge the battery during the day? As I understand it, you should avoid discharging batteries past the 50% mark since it shortens the life of the battery significantly. I was also looking at batteries made by Trojan but they are heavier and don't seem to have as much capacity as the one from Interstate. I would have to run 2 Trojan batteries in parallel to get comparable capacity to the one large Interstate battery.



Anyone know of any good websites where I can learn more about solar systems for rv's?

 

[klenger]

Anyone know of any good websites where I can learn more about solar systems for rv's?

Start with the link in my sig and go from there.



Good luck.

 

[Casey Balvert]

In my experience most battery manufacturers overstate the capacity and to be safe you might as well deduct 25%. Also you can't drain the battery completely as stuff just won't run at 10. 6 volts that manufactures use as a depleted battery measurement. Motors will run slow, inverters (even small ones) will shut down, and the tv picture will shrink long before you reach that voltage.



The only batteries that I found that would actually deliver what was advertised were gel cells that were very expensive. Cost per amp your available seem to be lowest with a decent golf cart battery. I use four in my trailer and the new rig will have six.



To be safe I use about 65% of the rate capacity as being available in the real world. In other words, if I have a battery bank of 450 amp hours (rated) then I realistically have about 300 amp hours available to me. There are other variable such as Puekarts coefficent (did I spell that right?) but my real world experience has shown that to be pretty close. And you are right, the less you discharge before recharging the longer your batteries will last. I try not to go below 40% of the actual battery capacity. You should consider an energy monitor such as the one I have from Cruising Equipment to monitor your system.



By all means. Check out Klenger's site. Tons of good info on there. I am going to steal his plans for the inverter set up.



Casey

 

[B-Ark]

Just doing a few simple calculations - 6 hrs x 25 amps x 12volts = 1800 watt hours. Assuming (optimistically) 10 hours of sunshine, you would need 180 watts of solar panels. For reasons suggested above, and others, I would suggest a minimum of 300 watts of solar panels.



Good luck.

 

[cjohnson1]

Here is a Solar power & Motorhome Web site for you with the answers your looking for. Chris has done his homework on this subject and has a couple of good links built in.

CurtisJ

 

[Prairie Dog]

Originally posted by B-Ark

Just doing a few simple calculations - 6 hrs x 25 amps x 12volts = 1800 watt hours. Assuming (optimistically) 10 hours of sunshine, you would need 180 watts of solar panels. For reasons suggested above, and others, I would suggest a minimum of 300 watts of solar panels.



Good luck.

Unfortunately batteries dont take a charge with 100% efficiency. If I remember correctly it somewhere around 60% so you'll actually need more like 400 to 450 watts of charging power.

 

[klenger]

Also keep in mind that solar panel rating is based on direct sun at 90 degrees to the panel, a situation that you will never acheive if the panels are mounted flat on the top of an RV.

 

[Diesel Gunner]

I just replaced the batteries on my TT with two six volt golf cart batteries in series. I will be heading out for the weekend and am looking forward to seeing how they perform. I bought them at Sam's for about $46 per and had to buy two more battery boxes to modify things. The Golf Cart batteries are about 2. 5 inches taller than the originals, so I cut the tops off of the old boxes and married them to the new ones to make them taller.



I carry a 2200 watt Honda to power up the micro and run the hairdryer for my girls. No TV, no computers, only an amfm radio.



I am interested in solar. Primarily to eliminate running the generator. We do alot of fall and winter camping and hunting which means that there is not alot of strong sunlight, especially under the trees. I also doubt that the panels will work once they are covered with snow.



One last item, I will testify to shortening the life of batteries by drawing them way down. The batteries that I just replaced were only 27 months old and I had let them go completely dead about three times. Also, on several occassions, I had drawn them way down. I did not feel that the gell batteries were good in the value to dollar catagory, so I decided to try the golf cart batteries. I will post when I get back on how I feel that the GC batteries perform.

 

[EricBu12]

Guys!,

I have done some Solar testing on my new 28' toyhauler.



I have 2 50 watt panels that are able to hook together then run into the wires that was done at the factory. I then bought a controller to mount inside the trailer so I can see what the panels are doing. This thing is nice, when the solar is charging, it gets up to a certain voltage then cuts off till a lower voltage... anyway, when out camping, my 2 panels at direct sunlight (or as close as it gets) makes 4 or 5 amps into the battery. any bit of angle or dim light severly diminishes this to like 2 or 3 amps.



Earthroamer said on his new ford camper he has 2 185 watt panels to charge the batteries. that means he might be able to charge at about 15 amps or so in direct light.



Solar panels are expensive and to have enough for stand alone power means you need to pay. My trailer also has a generator built in with the fuel tank for the toys, it works well. I use it for the micro and to sup. the solar charge.



I would recomend at least 200 total watts of solar panels. here is the site where you can get the one I have

http://www.icpglobal.com/html/pnp30100.asp

Go to the product video in the top right corner to see how my system works.





here is the controller

#ad








And the panel

#ad

 

[EricBu12]

heres some pics of my setup



The solar panels mounted on the roof

<img src=https://www.turbodieselregister.com/user_gallery/sizeimage.php?&photoid=6661&width=2/src img>





This is the connector for multiple panel hookups.



<img src=https://www.turbodieselregister.com/user_gallery/sizeimage.php?&photoid=6662&width=2/src img>





This was taken at 9 am mountain time and the batteries are already charged as you see the green LED in the middle, when the battery voltage gets down to 12. 6 or so, it comes back on as much as the sun will allow til it reaches 14. 4 volt then it cuts off again

<img src=https://www.turbodieselregister.com/user_gallery/sizeimage.php?&photoid=6660&width=2/src img>



And this is the electric panel (sortof) and you see the controller, the generator remote, and the ALL important radio/CD player!



<img src=https://www.turbodieselregister.com/user_gallery/sizeimage.php?&photoid=6659&width=2/src img>

 

[slo-ryde]

It looks like I'm going to be needing 150 watts of solar panel to start with. That should give me an average of 100 watts since the panels would almost never be in perfect alignment with the sun and there's always something getting in the way (clouds, rain, trees, etc. ).



I'm going to stop in Quartzsite, AZ on my way out to pick up the trailer and visit Solar City. They seem to have all the details of solar power systems worked out.



I like the ICP panels for the plug and play feature, it certainly makes adding another panel real easy! Eric, thanks for the pics!

 

[dabubba]

I'm a local Solar Dealer in your area- All of my larger RV system are a plug and go type- I've been using BP and sharp solar modules which both have a 25 year warranty- I have 150W on my RV now and am running about the same amount of power as you are talking about- I'm in the process of adding more power. I have put a few 240W systems out there and have had rave feedbacks for my customers Oo. If you are interested IM me with your info I can work with you or refer you to my dealer in your area.

 

[Turbo Horseman]

Soliciting hussy.

 

[RedRamer]

Here's a site where I started off when looking into this battery problem.

part 1

http://bart.ccis.com/home/mnemeth/12volt/12volt.htm

part 2

http://bart.ccis.com/home/mnemeth/12volt/12volta.htm



Very well researched articles, I print and carry with me.

I ended up with 2 golf cart bats and a Honda 1000eu and changed my Magnatek converter to the electronic one.

It's noisier than panels but up here we don't get the sun you guys get.

Problem is, it still takes over 3-1/2 hours to charge up batteries, and even then... .

 

[dresslered]

Here's a question:

I'm going to add some solar panels (200-300 watts) with an appropriate charge controller to my Bigfoot camper and was wondering whether or not the circuit has to be disconnected when when utilizing another source:



1) Camper battery is charging from truck alternator while driving.

2) Camper is running on AC power (hook-up or generator).

 

[klenger]

dresslered



I leave my solar connected all the time, regardless of other charging sources in use. Works just fine.

 

[slo-ryde]

I guess the answers would depend on how the trailer is wired. I'll use the trailer I'm buying since I know what's in it and how everything is connected.



The trailer has a 55 amp magna tek converter/charger. When plugged into shore power it provides DC for everything in the trailer that runs on DC and also charges the batteries. When you remove shore power the converter/charger shuts down and you start running all things DC directly from the batteries.



When a solar system is installed it will charge the batteries through it's own charge controller. It will continue to charge the batteries until the voltage across them indicates that the batteries are full. It will either shut off or continue to apply a float charge at that point (depending on the style of charge controller).



So, I would think that the solar charge controller could probably be left on when you're charging the batteries from the truck. It would "see" that the voltage across the batteries indicates they are fully charged and would simply stop providing charge current to the batteries.



My guess is the same thing would happen when on shore power. One downside to the converter/charger in my trailer is that it will overcharge the batteries. If left on shore power long enough it will cook the batteries, literally boiling off the water and exposing the plates. I'm going to be looking at some way of controlling the charger function from inside the trailer. The plan is to allow the charger to bring the batteries up to full charge and then allow the solar panels to apply the finishing/float charge. I'll be replacing the converter/charger unit in the future (when the money tree recovers from the last pruning) with an inverter with built in charger. The charger in the newer inverters is a 3 stage style. This style will charge the batteries but is smart enough to reduce charge voltage once the battery reaches full charge.



There's probably a control panel available that would allow switching the various charge devices on/off for you. I'm still learning how all this stuff works. If I find one I'll post the info here.

 

[dabubba]

Dave,

The charge controller monitors the battery voltage levels and will disconnect the solar charge when the battery voltage reaches the voltage set point--- I'll be at the Ram Runners this Month- I'll bring some info---- Curt

 

[dresslered]

Thanks for the replies. I would like to have faith that all will work fine but being an electrical engineer, I can see potential problems. Without true wiring schematics, I have no way of really determining the effects and have to fall back on faith again.



Granted, most decent solar controllers are pulse width modulated and shut down at a set battery voltage. The question arrises if the solar controller is set higher than the ac-dc converter or the alternator in the truck. Do we really want the current flowing back into the truck or forward into the panels? I was thinking of a beefy FET circuit to reverse-isolate the solar charger as well as providing a minimal forward voltage drop--I've actually heard that some solar controllers set the voltage upward of 18-volts!??? Also, I do have an accurate incab digital ammeter which would show how much and which way the current is flowing from the truck to the camper, but I am sure that this has all been solved before. Look forward to seeing your info Curt.

 

[EricBu12]

Dresslered,



The units in the pictures on the previous page is my setup.



The controller has an adjustable Set point for the cut off. Default is 14. 4 volt but you can adjust it any where you want



. It has a built in one-way "valve" for the electricity to go only to the batteries and not go back into the panels.



I can get a reading on the amps going into the batteries and I know that whenever I need the trailer, the batteries are always full charged. For ease of install and use, this is the best system.



It can even be portable, just set it out in the sun or store it away... ... .