Solar Newbie Needs Help

[robyneller]

Hi everyone,

I've been studying a lot over the past 3-4 months trying to educate myself on solar power. I'm now familiar with the very basics, but my brain still smokes a bit when I try to figure out how to set up my system.

I purchased a basic "starter" kit which I now realize was probably over priced for what I got, so I want to try to make the best out of my first solar purchase "mistake".

I purchased a Coleman (aka Sunforce) 18watt (1.2amp) solar panel kit. It came with 1-18 watt panel, a 7amp charge controller, and I also purchased a 450 watt power inverter, and a 32 amp hour deep cycle battery.

I'm only trying to power my aquarium filter, air pump and maybe the fluorescent light and the blower fan on my wood stove.


Wood stove fan: 76 watts, .64 Amps, 120 volts
Aquarium Filter: 15 watts, .12 Amps, 120 volts
Aquarium Air Pump: 8 watts, .06 Amps, 120 volts
Aquarium Light: 17 watts, .14 Amps, 120 volts (estimate)

My questions are:

1) How do I figure out how long I can expect the battery to run these few items with the set up that I have? It’s a 24/7 operation for these items. So I guess that would be 23.04 amp hours? Considering that's right, I still don't know what that equates to as far as my battery life and how long to recharge it on a sunny day.
2) Would it be a good rule of thumb to have one deep cycle battery per panel? Let's say I have 5-18 watt panels (90 watts total) How many batteries should I use?
3) How do I hook up multiple batteries in a row?
4) What size batteries do I need? Is the 32Ah one I have big enough for more than one 18 watt panel?

I believe I can have up to five of these 18watt panels (6 total amps) on the 7amp charge controller but the cost is way high and I could have a 100watt panel for less I now realize, but I'm willing to buy a couple more of these overpriced panels just to make a matching set if I need too.


Thanks in advance for your time and your help! I didn't know where else to turn for answers.

Thanks,
Robyn

[Sunking]

How many hours per day does each item run?
What is your location?

What I can tell you is what you have bought so far is pretty much useless except the inverter.

[robyneller]

All of the aquarium items will be on 24/7 365 days a year. So non-stop. The woodstove fan would probably be 24/7 during the winter.

I live in Maryland.

[Sunking]

All of the aquarium items will be on 24/7 365 days a year. So non-stop. The woodstove fan would probably be 24/7 during the winter.

I live in Maryland.

I was afraid you were going to say 24 hours. OK so lets run the numbers but you are not going to like it one little bit..

Wood stove fan: 76 watts, .64 Amps, 120 volts x 24 hours = 1824 watt hours
Aquarium Filter: 15 watts, .12 Amps, 120 volts x 24 hours = 360 watt hours
Aquarium Air Pump: 8 watts, .06 Amps, 120 volts x 24 hours = 192 watt hours
Aquarium Light: 17 watts, .14 Amps, 120 volts (estimate) x 24 hours = 408 watt hours.
Total Daily Watt Hours Consumed = 2784 watt hours or 2.784 Kwh hours

Maryland December Sun Hours = 2.9

Panel wattage required with MPPT Controller = [2784 watts x 1.5] / 2.9 Sun Hours = 1425 watts, Round down to an even 1400 watts
or
Panel wattage required with PWM Controller = [2784 watts x 2] / 2.9 Sun Hours = 1920 watts. Round Down to 1900 Watts.
Battery capacity required at 24 volts = [2784 watts x 5] / 24 volts = 232 AH, round down to 225 AH
MPPT or PWM Charge Controller = 58 Amps, round up to 60 Amps.

So there is what is required to do what you want. So nothing you bought can be used. You need to cough up another $6000 to do what you want.

Hope that helps.

Good Luck.

SK

[Naptown]

Hagerstown or west eastern shore where. It makes a difference. A zip code for insulation would help. I live and do this in maryland

[robyneller]

of course, duh, I wasn't thinking.

Zip is 20744.

I'm right at the DC/VA/MD line and right at the foot of the Woodrow Wilson Bridge.

Thanks!

[robyneller]

So there is what is required to do what you want. So nothing you bought can be used. You need to cough up another $6000 to do what you want.

Hope that helps.

Good Luck.

SK

Wow, so just to power an aquarium and a fan it would cost me about $6000! I guess I'm starting to see why solar isn't taking off that well. I kept wondering why isn't the world embracing this awesome technology that is practically free.....aaahhh not so free. Thanks for all the calculations! This really helped enhance my knowledge base. It will definitely be put to use for my future plans.

[Sunking]

Wow, so just to power an aquarium and a fan it would cost me about $6000! I guess I'm starting to see why solar isn't taking off that well. I kept wondering why isn't the world embracing this awesome technology that is practically free.....aaahhh not so free.

Free where did you hear that from?

The really fun part is the batteries need replaced every 5 years and those cost in your case roughly $2800. You can buy the same amount of power from the POCO for $520. With solar you pay it all up front in cash in 5 year increments. POCO bills you monthly for what you have used.

[PNjunction]

With the battery you have now, you would be able to run your 8W air-pump 24/7, and reach a worst-case of 50% DOD daily. BUT, with only 3 hours of solar insolation available, you'd need a little over 10 times what you have now in the panel - about 160 watts of panel, and a 10-15 amp charge controller just to run the air-pump. If you can turn off the air pump during that 3 hour recharge window, so much the better.

I went by the wattage rating listed for your air-pump and converted that to 12v usage (P/I*E), so 8w/12v = .66a when using 12vdc. If you are looking at current remember that the spec you listed was for 120v ac.

Ok, so it was a mistake, but if you want to continue with just that single 15w panel and only 3 hours of insolation, perhaps look into a small 7ah agm battery for charging cell phones - maybe a tablet once a day. I'm not trying to be a smart-ass, but that's the way it is. Maybe something like a Stanley 300 jumpstarter (7ah agm inside) would be a nice convenient battery-in-a-box to mess around with and be potentially useful. I'm not joking - I use a small 15w panel to charge it via the dc cigarette lighter jack (with CC in between of course). I have enough solar insolation to finish the job, but not in the dead of winter - the on-board float-charger of the jumpstarter takes care of those times. (but only charge via one source or the other, not both!)

OR, if you don't have a project, but just want to be able to use the existing battery for *something*, consider that you have half of it's capacity to play with which will take 160 watts of panel to recharge in one day in your environment. I'm assuming that's an AGM battery and at the typical max of 0.25C to 0.3C, you would just reach the max input current with that. If you plan on not using more than just 25 percent of it daily, you might be able to get away with an 85 watt panel and 6-10amp charge controller. Of course, now you can plan your loads to fit the battery capacity - which is the backwards way of doing it obviously.

Grab a 10-13 watt CFL bulb and run that from your inverter. I'll bet you'll get about 12-15 hours from your fully charged 32ah battery before reaching the 50% DOD voltage (around 12.2 for agm). Your single 15w panel won't recharge it in a day. Grab an inexpensive smart-charger and decent multimeter to keep the battery healthy and have some fun at least.

[robyneller]

Thanks PNJunction for the additional suggestions. At least I learned a lot from my $90 investment on the kit and I can always power a "Power Bubbles" 12 volt air pump off the battery for awhile.

How about this idea, I'll buy a standby generator and use the 18watt panel to trickle charge the generator battery.

[Sunking]

How about this idea, I'll buy a standby generator and use the 18watt panel to trickle charge the generator battery.

That will work.

[Naptown]

of course, duh, I wasn't thinking.

Zip is 20744.

I'm right at the DC/VA/MD line and right at the foot of the Woodrow Wilson Bridge.

Thanks!

OK you live in one of the best places on the planet incentive wise for solar but it has to be grid tie.
Say you put up 3 KW on your house cost before incentives would be about 12K
Now you get a 30% federal credit, 1000 state grant and 3000 property tax credit.
Total credits come to $7600 leaving you with a net cost of about 4400
That system will produce about 3600 KWH per year @ $.15 is $540.00 and renewable energy credits of abut 500.
That system would pay for itself in a little over 4 years. with another 20-25 years left of at that point free energy.

[robyneller]

Back with lower expectations this time!

Hi everyone, thanks again for the detailed assistance you gave me back in February. I've decided to only focus on THE BARE necessities for my solar power needs which is the air pump. I have a 6 watt, 120 volt aerator. I tried to use the info you provided before to figure out how to run just the aerator, but I wanted to get my work checked by the pros. Plus I need a little more help.

Ok, so 6 watts x 120 volts= .05 amps x 24 hours= 1.2 watt hours for 24 hours. Is this right? This doesn't account for power for the inverter.

I currently only have 1 - 18 watt solar panel and one 35 amp hour battery, a 7 amp charge controller, and a 450 watt inverter. I think I can have a max of 6 solar panels on that charge controller and that's about the max space I have also.

How many panels would I need and how many batteries would I need to run the air pump for 24 hours for 5-7 days? How many days would it last without any additional incoming solar charging during that period (worst case scenario no sun for days)?

Will 6 panels and 3-36 amp hour batteries run the aerator 24 hours for several days to a week or more? What is the minimum number of panels I could get away with? 4 would be optimal for my space but I can get 6 if I have to.

Thanks!!

[Sunking]

Ok, so 6 watts x 120 volts= .05 amps x 24 hours= 1.2 watt hours for 24 hours. Is this right?

No it is complete gibberish with no meaning

6 watts x 24 hours = 144 watt hours

Assuming 12 volt battery you would need a 12 volt 60 AH battery.

As for solar panel wattage goes depends on where you live and the type of controller you use. However for such a small system get a 60 watt panel and a 10 Amp PWM controller.

With that said forget the 400 watt inverter, the battery or panel cannot handle that large of an inverter. 50 to 100 watts max.

[robyneller]

Great! Thanks. I will go with this set up. My fish say thanks also.