FB Coach said:
I have read every post that I can find regarding solar charging for an RV. The amount of information out there is insane. Amp hours, PWN vs. MPPT, voltage loss, Amp storage etc?. I am overwhelmed at this point. I guess I?m just not very smart because I am at a loss. Someone please just tell me how many watts of solar panels to install on my trailer. I just want to keep my batteries charged without running my noisey generator. Here is the scenario:
We typically dry camp for two week spans.
We have converted every bulb in the trailer over to LED?s.
2 standard group 24 12v batteries.
We like to listen to the radio most days.
We will watch an occasional movie. 12v TV/DVD
If it is cold we will run the furnace to take the chill off, not make it so hot you could bake cookies.
The trailer has all the standard stuff that needs to be run.
In general what size panels do I need so I won?t have to run my generator? I will buy for x amount over just to be sure, but at this point I don?t know where to start.
Thanks
This solar thing is never easy and it starts with what area of the country that you live in. Here in Sunny SoCal, I have 160W solar array and it does a nice job for me. We regularly camp for 10-days straight. Our batteries have never run down while camping. We've even had several days of partly cloudy........ the key is having a battery bank big enough to get you through the bad days and panels big enough to keep the batteries full by 2
M on the good days.
2 weeks ago, we camped for 5 days at the beach. Woke up to leave at 5:AM on the 6th day and the battery voltage was 12.5V, after running the furnace all that night night (45* that night..... we leave our thermostat at 69*). BTW..... our panels are now 4-years-old.
I would recommend starting with either 2x 80W panels or 2x 100W and leave room for expansion That is buy a 20A controller.... it doesn't need to be an expensive MPPT controller with a small RV system. Also, use 8AWG wire from the panels to the controller and from the controller to the batteries.
That way you have room to expand your system by merely adding more solar panels, with no need to buy another controller or replace the wiring.
The other important item is be sure that you have approx 1 amp hour of battery storage for every watt of solar output. If you have 200W solar array, you will want a minimum of 200ah of batteries.
I installed my 160W system for under $500 (not including batteries) and the prices have since dropped. Today, you can get decent 80W solar panels for $140 each and a controller for $20........ wire, another $50-$60 (marine grade 8-2AWG wire). You don't have to buy exensive panels. The cost/reward factor is too great any more.
BTW..... don't drill holes in your roof. You can install the panel mounting brackets (panels should be raised 1.5") with 3M VHB tape (pt# 4941)
Check out this deal (same panels that I have)..... This price is a STEAL..... that's what I paid for each 1 of my panels, 4 years ago.
http://www.ebay.com/itm/160W-2-80W-solar-charging-kit-for-12V-battery-motor-home-caravan-80W-watt-panel-/251198136965?pt=LH_DefaultDomain_0&hash=item3a7c936285
I have this controller and it's done a fine job for the last 4 years:
http://www.ebay.com/itm/20A-Solar-Charge-Controller-Street-Light-Regulator-12V-24V-Autoswitch-Panel-PWM-/300839126207?pt=LH_DefaultDomain_0&hash=item460b68c4bf
Here's your wire.... be sure to get plenty....add 10' to whatever you measure.
http://www.ebay.com/itm/8-2-Gauge-AWG-Tinned-Duplex-Marine-Wire-Red-Yellow-PER-FOOT-/290844079276?pt=Boat_Parts_Accessories_Gear&hash=item43b7a874ac&vxp=mtr
Here is the 3M tape....
http://www.ebay.com/itm/3M-VHB-4941-Heavy-Duty-Double-Sided-Outdoor-Mounting-Tape-7-FEET-FT-/271173767169?pt=Motors_Car_Truck_Parts_Accessories&hash=item3f23375001&vxp=mtr
Fabricate some brackets to pop-rivet to the panels... bada-bing.... you have a system for around $350 + batteries..... if you find it inadequate (which I doubt from what you've said) add 2 more 80W panels for $280 (now your up to 320W) and you are still under $650.
The only thing that you do that we don't do is watch TV...... for that alone, I might suggest that you start with 3x 80W (240W). Even if you go with a 320W system, the 20A controller is just fine. Max output of 320W panels in perfect conditions (which is never) is 23A. The controller will handle that just fine. A friend of mine that camps with us regularly has that set-up. He even uses his microwave on the inverter but he also has a 450ah battery bank (4x 6V golf-cart batteries).
The big thing to understand is that you really can't do anything "Wrong" going with solar. Even if you just start with 1, 80W panel..... it will extend the length of time that you can go without charging the batteries. To ME... the key is starting with a minimum of a 20A controller and 8AWG wire. That way, expansion of your system is simple. Just keep adding more 80W panels (I just use 80W as an example) until you get it right.
The issue that you have is that you may want to replace those group 24 batteries with 2x 6V, deep cycle golf cart batteries at some point. That will be about $350 for decent ones.
The issue is, the solar panels work during the day when battery use is low. Battery use is highest at night, when there is no Sunlight. The batteries that you have will more than likely not get you through those partly cloudy to rainy days. However, that's something that you can face when the time comes. Replace the batteries with better ones when they need replacing.
Adding solar doesn't have to be complicated or painful. You really can't do anything wrong and as long as you stick with multiples of 80W or 100W panels, it's all good, no matter what. Just keep adding.