rv solar set up suggestions batteries, controllers, and inverters?????
dannycoffin
Registered Users Posts: 1 ✭
I am buying an rv soon and studying Solar energy I was considering an 800 watt solar array, connected to 4 110 amp 12 volt batteries. Should I run them in series or both parallel and series for higher voltage would that be 24 volts at 220 amps and amps or run them 4 for the 440 amps, if I run the 24 volts do I need a diferent inverter, and suggestions on solar controllers, what I would use it for would be tv, computer, lights, short microwave, video games. a dyson fan-heater there low amp and seem to work good, coffee pot. some one informed me that I shouldn't drain my batteries daily lower then 20% to 30% for long term use. Suggestions on inverters sine vs other,how many watt inverter should I get? should I get a mttp controller. when you run a battery bank do they connect directly to the rv power source like the rvs plugs like an 30 amp outside connection to the fuse box, or do you run battery bank separate and use the plugs in the inverter. some people use 6 volt batteries with higher amps how do they perform cost effective. Is there anything else I need to know? Thank You
RV and Solar Newbie
RV and Solar Newbie
Comments
The first step in designing a system is to know the purpose of the system. The purpose of the system is to power your loads. So, what are your loads? You need to know the peak load (watts) and the daily energy usage (kilowatthours).
We have all sorts of formulas to calculate battery size, size of array, etc... but these formulas use numbers. In order to help you, we need to know your energy usage numbers. Similarly, if you asked us what pickup truck to buy for your trailer, we couldn't answer without knowing the weight of the trailer.
Some of your loads may be problematic if you only have 800 watts of array... electric heater, coffee pot, microwave. What about refrigeration? Air conditioning? water pumping? Do you have a generator? Do you have the capacity to carry a thousand pounds of battery?
--vtMaps
There are several solar design stickies of how to calculate your loads, how to size the batteries for them, and finally calculating the size of the PV array to recharge.
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
Get a handle on your loads. Figure out what you will run, what the power draw is and how long each one needs to run. Until you do that, you are sort of just peeing into the wind
Once you have a list of your "wants" you can get GREAT input from the experienced folks here, on how to balance what you want and what fits your budget - whatever it is.
Investing the time at this phase is a critical step to success!
Marc
Vtmaps' and others' suggestions are correct - know your loads. However, 800W of panels on an RV roof probably won't generate as much power overall as the same amount of panels on a house roof, because RVs often are not oriented ideally to the sun or are partially shaded. For this reason alone, I suggest carpeting your roof with as many panels as will fit! PV is still cheap, so a few more panels aren't much more in the context of what the RV will cost you anyway. Just don't put panels next to roof-mounted A/Cs or stink pipes or fridge vents or whatever sticks up above the roof - even the slightest partial shading such as from RV roof impedimenta will drastically reduce their output. If you can mount your panels on tiltable mounts they will produce slightly more power in the summer but probably appreciably more power in the winter when the sun is lower. 1000W of panels is about the most that a charge controller can handle for a 12V system (which your RV is). If you can charge your batteries at a 10 to 13% charge rate they will charge quickly, maybe allowing you to also power opportunity loads in the afternoon after they're fully charged, such as power tools or a washing machine or other non-time-sensitive but power-hungry loads.
Have fun!
John
40' Crown bus with 2kW of tiltable panels on the roof:
Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.
Southern California
-Bill
-Bill
I live up in the Northwest and that panel wattage to batteries amps wouldn't work out very well as often you can go days without sunlight, possibly a week to a couple of weeks, then several days with sunlight. Depends on you location and altitude, weather in the mountains is usually not the same as weather along to coast, low lying areas, etc. There are areas that average over 150 inches of annual precipitation, 20 miles or so away only around 20 inches of annual precipitation.
For up here in the Northwest I would want more battery storage as I never know how much sunlight will be available.
However the previous comments are correct. You also need to figure the demand or common daily loads. Do you require AC, TV, Computer, Microwave, etc.?
When off-grid a stock RV won't operate without a certain amount of 12 volts power to run a Fan for RV furnace (which often are 7+ amps, check the amp rating of your RV furnace) and 12 volts to run the RV gas absorption refrigerator. (12 volts is normally required for a RV gas frig to operate) Plus a few other items such as the water pump, bathroom and stove fan.
What I did with my RV was to install an additional Catalytic Heater in the RV that requires no elect. to operate. It's best to get a catalytic heater built for an RV such as Olympian or a heater that designed for a permanent installation. One that puts out a constant heat where the btu ratings may not be as high as portable camping heater, etc. These are much more reliable and maintain room temperatures throughout the day and evening.
When the batteries become drained it often requires from a half to a full day to recharge (sometimes a bit longer, depending on the size of your battery bank). If no sun a geny is usually relied upon. Also it's not a good idea to run batteries below 50 percent then recharge again, potentially shortens the life of the batteries. As a general rule you want to try to keep the batteries maintained and charged somewhere above 50 percent of their capacity. At least this is what I have read about charging battery banks, perhaps others have other ideas about keeping batteries charged.
Jim
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Basing the inverter on charger capability may lead to choosing a much larger inverter than required (eg 2500w), which means higher self-consumption just to have the big inverter supplying small loads. A big inverter can use 30-50w on top of the small load, which could be (eg) 40w x 24hrs = 960wh/day. The bank will be [email protected]= about 8kwh. You don't want to run in down more than about halfway, and a 2500w inverter can get there pretty fast.
Using 3 strings of batteries in parallel isn't ideal. You'll want heavy, short interconnect wire, quality connections, and a fuse on each string. A clamp-on current meter would be helpful to ensure balanced charging.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Jim
Two strings (eg. 4x350ah 6v L16 type batteries) can work if monitored carefully. I use this setup for my 700ah 12v bank, and it has worked well. As the number of strings increases, so does the difficulty in keeping strings balanced. Three may work okay with your good connections, and regular monitoring and maintenance. If one string is reading low during regular specific gravity checks, it should be charged separately to get it to the level of the other strings. 6v GC type batteries are nice in that they're widely available and generally pretty cheap for their capacity, so it may make sense to use them anyway. It's just a bit of a trade-off in terms of a bit more careful monitoring and possibly periodic remediation with the three strings. With more than two strings, you should also fuse each string as well as breakers on the controllers and inverter, because a short in one can put the current available from the remaining strings across the short in the bad one.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
I agree with those who say run your AC appliances in the peak generating hours of the day. I also agree, using propane for coffee. That Coleman stove-top drip coffeemaker is pretty cool, just be sure you have a spare carafe in a soft, safe place, or an alternative you can use until your new carafe arrives. But I'd also say, you can run your AC more if you're using lithium-iron batteries (LiFePo4) because you can draw them down 80 percent, as opposed to lead-acid's 50 percent usable power.
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada