# New to solar need some help

Solar Expert Posts: 31
Hi everybody, I'm new to this forum and solar energy. It's kind of interesting to me when it comes to green energy have been doing research online, i guess i found the best place where solar experts hangout 8) and i can get some advice to setup a solar off grid tie system to run applications. I'm thinking putting up a 100w solar panel on my backyard, we get a lot of sunlight from morning to 4ish PM before the sunlight becomes weak or block by neighbor trees, and i live in LA if you are curious hehe.

Long story short, i want to run a fish tank pump rated at 15W for 24/7 and maybe run a 56W light for 5 hours or so. I found a 100W 12V solar panel on ebay made by a company called ramsond dont know if anybody heard of this company. I need some recommendations for: charge controller under 150 USD, and what battery should i go for?

100W 12V solar panel by ramsond
Xantrex prowatt SW1000 1000W true sinewave inverter

ramsond
UL Solar panel
What do you guys think of these two panels or should i get something else?

Thanks guys.

• Solar Expert Posts: 87 ✭✭✭✭
Re: New to solar need some help

1000 watt inverter sounds like major overkill for 71 watts of load. All inverters have a loss involved as a percentage of their total output. If you don't need 1000 watts get something smaller and closer to what you really need.
Re: New to solar need some help

OK, using PV Watts for Los Angeles Ca, the average amount of Noontime equivalent sun per day is:
```Month  Solar Radiation (kWh/m 2/day)
1      4.44
2      5.35
3      5.62
4      6.06
5      6.19
6      6.17
7      6.48
8      6.68
9      5.78
10      5.43
11      4.84
12      4.46
Year      5.63
```

And the amount of power you use is:
• 15 watts * 24 hours per day + 56 watts * 5 hours per day = 640 Watt*Hours per day

Assuming 4 hours of sun minimum (winter with some evening shading), and 0.52 system derating (all losses for off grid battery system):
• 640 WH per day * 1/0.52 sys eff * 1/ 4 hours of sun per day = 308 Watts of solar panel minimum

Battery bank size assuming 12 volts:
• 640 WH * 1/0.85 inverter losses * 1/12 volt battery * 2 days of no sun * 1/0.50 maximum discharge = 251 AH @ 12 volts

Or, roughly 2x 6 volt @ 220+ AH golf cart batteries in series for a 12 volt bank.

There are still a lot of issues to discuss--but that is a back of the envelope to set your expectations.

If you could find a 15 watt 12 volt DC pump/aerator/water mixer, you could save a fair amount of energy (inverter losses may be almost as large as your air pump in this system--or possibly even more if you use the 1,000 watt inverter).

Another issue is what happens on dark/rainy days--Will be there to monitor the system or switch it over to AC power? Lead Acid batteries do not like being run to dead--They generally will not recover and last more than a week or two, especially after they have a year or so of use.

-Bill

PS: I can't say much about the panels (I am not in the business--So no experience with them or the vendor). By the way, the two links go to the same Ebay auction.
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 31
Re: New to solar need some help

Thanks guys, i understand there will be losses, the reason i picked that inverter because i want to do future upgrades etc maybe i should get either xantrex prowatt 600W or morningstar 300? the DC output will go in to my garage where i'm planning to keep the controller, inverter and battery.

any suggestion on what type of battery and controller i should use?

thanks again guys appreciated.
• Solar Expert Posts: 3,009 ✭✭✭✭
Re: New to solar need some help

Re inverter, as was mentioned already, the idle wattage consumption of inverters tends to go up with the size of the inverter. I use a Morningstar 300 watt inverter, on 24/7 to run practically everything in the house, including this computer, Sat receiver, TV, all inside and outside lights and 200 watt slow cooker + too many other things to mention, and have been doing so for years without a hitch. It basically runs the house. The bigger inverter is on standby/search mode for large loads only, loads like the water pump, washing machine, Band saw, toaster oven etc etc that only it supplies. The small inverter draws 6 watts on standby, the large one at least 20 watts, just to run it.
• Banned Posts: 17,615 ✭✭
Re: New to solar need some help

"Future upgrades" is one of those things that aren't so easy to do with solar. You need to look carefully at what you have/need/want now and what it will be "then". Too often the two designs will be so different that almost nothing can be saved for later use.

As Bill has demonstrated, your one 100 Watt panel won't actually meet the Watt hour needs you have now. As cruiser guy pointed out that inverter is going to use a lot of power on its own, and that's power you haven't got.

So right away it's decision-making time: do you buy more equipment now? If so, how much? Enough just to meet your needs at this moment? Or do you go whole-hog? Only you can make those choices.

In ballpark terms, your 100 Watt panel will supply about 250 Watt hours AC out the door. It could fully charge about 64 Amp hours of battery, which at most would give 384 Watt hours DC (from which all loads draw, including the inverter - thus the difference between AC and DC Watt hours). Can you do something with that? Or do you need to spend more money now?
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: New to solar need some help
intel415 wrote: »
Hi everybody, I'm new to this forum and solar energy. It's kind of interesting to me when it comes to green energy have been doing research online, i guess i found the best place where solar experts hangout 8) and i can get some advice to setup a solar off grid tie system to run applications. I'm thinking putting up a 100w solar panel on my backyard, we get a lot of sunlight from morning to 4ish PM before the sunlight becomes weak or block by neighbor trees, and i live in LA if you are curious hehe.

Long story short, i want to run a fish tank pump rated at 15W for 24/7 and maybe run a 56W light for 5 hours or so. I found a 100W 12V solar panel on ebay made by a company called ramsond dont know if anybody heard of this company. I need some recommendations for: charge controller under 150 USD, and what battery should i go for?

100W 12V solar panel by ramsond
Xantrex prowatt SW1000 1000W true sinewave inverter

ramsond
UL Solar panel
What do you guys think of these two panels or should i get something else?

Thanks guys.

you are overlooking the first very basic thing here. you have far too much load to expect a 100w pv to cover.

you may see about 77w out of the pv and if over 5hrs (being lucky enough to have 5 full hours of sun at 1000w/m^2 everyday) you would see 5 x 77 = 385wh.

56w x 5hrs = 280wh
15w x 24hrs = 360wh
640wh subtotal
inverter operational losses can up consumption at least 10-20% or more and add to that the idle power used by the inverter when not used but on and you've got dead batteries now because the pv couldn't keep up with your loads. icarus has a little formula for roughly figuring this and i'll let him inject that here on this thread, but you will most likely need to at least go 2.5 to 3 times the pv wattage you figured. also be aware your battery will need to cover those loads with only being drained no more than 50%. it isn't cheap to get into solar, but it is cheaper than it's ever been.
• Solar Expert Posts: 31
Re: New to solar need some help

Thanks for the input guys. Yeah i think overlooked a 100W pv can produce 100% of power lol

New setup

2 x 100W PV
Morningstar Prosta 30
Morningstar 300 inverter
1 12V Trojan T-1275

Fuels, wires i can purchase from local stores. How is this setup now? Let me know what you guys think thanks.
• Banned Posts: 17,615 ✭✭
Re: New to solar need some help

Well two 100 Watt panels will produce twice as much power as one. So you'd get about 500 Watt hours AC and could use around 128 Amp hours of battery. By my calculation that still leaves you short of the 640 Watt hour load desired.