Forum Discussion
- CincyGusExplorer IIUnless you're actively going to move the portable panels and tilt/position them multiple times a day to see that they produce significantly more than mounted panels, I think Mounted are the way to go. Mounted seem to have better/longer warranties and they are pretty much mount and forget about them. Portables you have to have a decent place to store and then there's the setup, hook up and tear down every time you go camping. Just my two cents.
If your just looking to maintain the batteries between uses, 1-100 watt panel will do that easily. If your looking to keep the batteries charged while camping, an assessment of what you use would be critical to getting that decision right.
Identify what batteries you have so you can figure out how many Amp Hours (AH) they have. Generally, you only want to use 50% of those AH because going below that damages the battery and makes it store less energy upon future recharges.
I'm just going to make up some numbers to illustrate.
So say your batteries are 50AH each. You can take them down to 25AH each without damaging them but then they need a recharge.
So that gives you 25 AH of power to use between fully charged and need to stop and recharge. Now if your your usage is only 10AH a day, you will have 2.5 days of power without solar. If your usage is 25AH a day, you need to recharge daily and more importantly, you need to fully charge your batteries to be able to use your full 25AH again the next day. If they don't get fully charged, your going to be using more than 50% and damaging your batteries if you use your typical 25AH.
Next thing to consider is that solar panels are rated for a specific output but that is is optimal conditions. If you partially shaded because of a tree, or it's a partly cloudy day, or worse yet, it rains all day and you get nothing from the panels. So you want a generator as a backup plan for those days or if you need to assist the panels in getting back to 100% charged batteries. But many people put as many panels as they can which gives a quicker recovery of their batteries but most importantly, gives them a chance to get fully recharged to 100% even if they only get a partial day of sun.
The last consideration is going back to the Batteries. Adding more powerful 12v or (2 or 4-6v in parallel is the favorite configuration for many people) batteries that have higher AH ratings (Stores more power) makes your energy piggy bank much bigger. If you had 2 batteries that gave you a total of 300AH and you could use 150AH a day (Remember the 50% rule), well now your 25AH usage isn't such a big deal. You have 6 days worth of usable energy. A couple cloudy days wouldn't even make you fire up the genny.
Even though the numbers are made up just to make the math easy, I hope this helps you understand the process of deciding what is right for you (and others that may read this). There are a lot of moving pieces to think about but it really boils down to these three things:
* How much energy do you use/need daily
* How much can your batteries store
* How much can the panels reasonably put back in a day
Until you know the first one, it's like asking how much water should I take on my desert hike?
(Usage) How much do you need to drink each day?
(Batteries) How much can you carry?
(Solar Panels) Are there any oasis's to refill along the way? - sgfryeExplorerI use a renology kit with 2 100 watt panels and 30a controller i bought off amazon and it works great to charge 2 12volt rv batteries and 2 12volt boat batteries at home. I mounted the panels on an old 2 wheel hand dolly to make them easily to move and manuever. We dont boondock but if we did i would build portable frames with adjustable tilts out of pvc tubing from plans i found on google.
- pianotunaNomad IIISome where between 60 and 150 watts per 100 amp-hours of storage.
Do an energy audit so you know how much demand there is. - The_ugly_duckliExplorerMy roof would fit 6#, 100 watt panels and still have room to maneuver around. They feed into two 100 amp Battle Born lithium batteries. Will eventually add one more 100 amp battery. The setup easily takes care of my need. My 2000 watt inverter runs our Microwave easily. I haven't come across any restrictions with my current setup.
- 2112Explorer II
pianotuna wrote:
Don
Some where between 60 and 150 watts per 100 amp-hours of storage.
Can you clarify this? I have a 100Ah battery but 50 usable Ah. Would I consider 50 or 100 as my "storage"?
The question of 'how much solar' comes up in my circle from time to time.
I agree with performing a realistic audit
Thanks - BFL13Explorer II
hedgehopper wrote:
How many watts of solar panels would I need to keep two 12-volt batteries charged? I don’t know the specs on the batteries. I’m looking for a ballpark number.
What about portable panels vs those mounted on the roof?
Keeping them charged means they are already charged and you are "maintaining" them. There are solar trickle chargers for that.
If you mean while camping, you don't give any scenario to answer the question.
Generally, you first need an idea how many hours of sunshine you will get in a day, and how many amp hours of battery bank you need to restore daily. Divide the AH by the hours and that's how many amps.
You can find the amps a panel will do at high noon--eg 100w does 6 amps. But the sun goes up and down so you need an average amps over the whole day. Pick a number. That times the hours per day is your expected AH haul.
Get enough solar so you can haul in more than you use daily. Oops except is that in summer or winter? Enough for winter is more than you need for summer and enough for summer is not enough for winter. - red31Explorercorrective equalization requires current, 60w/100ah maybe on the low side.
- BFL13Explorer II
red31 wrote:
corrective equalization requires current, 60w/100ah maybe on the low side.
Assumes solar is the only charging method he has. For a weekend warrior it is valid to lose capacity every day with solar just slowing down how much you lose, then charge to full on shore power at home.
How much solar you need is all about scenario. - Kinda like asking how long is a rope.
- hedgehopperExplorer
RedRocket204 wrote:
This pretty well describes our situation except that we have a truck camper not a trailer.
200W will get me by with limited usage of 12V items in the CO mountains, late fall boondocking. That includes 2-3 hours of some LED lighting, USB phone charging, CO detector, fridge running on propane, some water pump usage and the big one, heater fan kicking on with the thermostat set at 52f and outside temps dropping into the teens f. My TT is considered a 3-season trailer with decent insulation but I don't have separate tank heaters. With two Group 24 12V batteries, I do get pretty close to 50% discharge rate by the time the sun comes up.
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