Solar panels!

......The Renogy solar panels have been on the roof for a couple of weeks now, charging a bank of 2 6v golf cart batteries. So far things are going great. The batteries seem to be charging to within the acceptable range during the day and the fridge has stayed cold throughout. My electrical needs are simple. The fridge, an Edgestar top loader is the biggest load. There are also interior lights (two), a water pump, a small fan, a TV/VCR and a small DVD player....all 12v. The only hiccup is that the TV/VCR seems to need a higher voltage (13v) than the batteries can provide over time. The TV works fine while the sun is up and I can watch a couple of movies at night but there is no way I could do a Star wars marathon. I may be able to stretch the movie watching out by adding a couple of more 6v deep cycles which I am planning to do anyway.
  I have not had multiple days of  'no sun' so I don't really know how deep my battery backup is. The charge controller seems to go into float mode every day so when I come home the batteries are topped off. I am interested to see what a few really cloudy days does to my power....or maybe not. I will likely purchase a couple more batteries in the next few days. As it stands I am using 2 6 volt golf cart batteries wired in series to give me a 12 volt bank. The batteries are listed as having 216 Amp Hours and knowing that I never want to discharge below 75-80% that does not leave much of a reserve. 2 more  batteries (6 volt wired in series) should up my AH capacity to 432 AH giving me about 115 AH if I don't discharge over 25%.

Sizing My System

It is strange how there is so much conjecture on the internet about bank sizing. I scoured every website I could find and got a general idea of what I needed but it was (is) still part guess work. 

  My needs are simple, basically those listed above and really everything based around keeping the fridge cool. Here is a complete list that I based my system around...

• Edgestar fridge / 6 amps when running
• small fan / 2 amps when running
• living room light / 1 amp when on
• hood light over stove / 1 amp when on
• hood fan over stove / 2 amps when on
• demand water pump / 7 amps when on
• portable DVD player / 1-2 amps when on ??
• TV/VCR combo / 3 amps when on ??
• cell phone charger / 1 amp when on ??

A grand total of ......Who Knows!

These are approximations and only for when the item is being used. Standby power on the fridge , for instance, is unknown. The fridge is always on but the amp usage is higher only when the compressor cycles.

My best guess is that I use a total of  111 AH a day. Again, this is a guess. I estimated high for all of my fixtures. As you can see, 111 AH per day brings my battery bank dangerously close to the 50% discharge mark so another couple of 6v batteries is in order.

I also plan to add some things....

• 12 volt ceiling fan
• 24" 12v LCD TV/DVD
• more 12v lighting (LED reading lights 1 watt each)

Sizing the system is important but I did not want to overspend. The panels should be good for 20 or so years but the lifespan of a well cared for battery can be as little as 5 years. I bought 6 volt deep cycle (true deep cycle) batteries and not Marine dual purpose batteries so that should help the lifespan but keeping the DOD (depth of discharge) as low as possible is important too. You don't want too few batteries because they will get discharged too deep but buying too many is just a waste of money. There are good calculators on the net and spending some time evaluating your needs will save hundreds in the long run.. maybe thousands.

   Another note...I have been thinking about this system for a long time and have been accumulating 12v appliances. The only thing that runs off an inverter is my laptop (to charge) and that is only a 100 watt inverter. 12 volt appliances, lighting, and fans are easy to find and you won't lose energy converting your battery power to 110V AC. Just food for thought.

Some Helpful Websites..

Here is a great solar calculator for figuring out your daily usage. I came up with about 87 AH on the high side....

http://www.advancepower.net/advcalc.htm

Here is the package that I bought.....

And here is a link to the batteries that I am using....

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_6-volt-golf-cart-electric-vehicle-deep-cycle-service-battery-115ah-autocraft-golf-cart_2100013-p#fragment-2

And some of the gizmo's that I use in the house...

I hope this information helps....