The first thing to plan is to work out what you will be wanting to power from your system, as mentioned in my previous Instructable, the whole of your house would be nice but seriously expensive and definately not portable. My system will only power small items such as an LCD TV, a couple of 12V energy efficient lightbulbs, a free-to-air receiver, a CD player and radio and to charge mobile phones and other miscellaneous items.
With your power intentions in mind it's important to now figure out the prices for each of the components, I wanted the best of the best so I settled for a top of the range PS-30M 30 Amp Morningstar Charge contoller from Sunstore.co.uk at £198.00 or $315. http://www.sunstore.co.uk/Morningstar-Prostar-30M-Solar-Charge-Controller-with-LCD-Display.html
This charge controller uses Pulse Width Modulation (PWM) to float charge the batteries once fully charged to maintain them whilst incorporating an LCD display to show the battery voltage and solar input current.
For the batteries I went for two Trojan T-105's, being six volts a piece to total 12 volts at 225Ah, this meant that the storage capacity of this bank would be huge, enough to power high drain devices for many hours.http://www.ebay.co.uk/itm/TROJAN-T105-BATTERY-/130296299020?pt=UK_Lifting_Moving_Equipment&hash=item1e5643be0c
With my two previous generations I used Maplin Electronics and Ebay to source all of my components but this time money wasn't as much as an object so I ended up splashing the cash on a multitude of sites.
The main items to power from the system are then used to calculate just how much power is needed and generated. The LCD TV and receiver draw 2.2 Amps DC on 12 volt, energy efficient lighting draws just under 1 Amp for a 12 watt bulb whilst the phone/GPS chargers draw very little power. Using the TV for say, 3 hours a day max would equal 6.6Ah consumed, lighting used for 4-5 hours a night would consume roughly 4Ah while all the charging of portable devices would be around 2Ah while pumps for air-beds wouldnt run for long so maybe only consuming around 1Ah, totalling 13.6Ah. Deep Cycle batteries shouldn't be discharged below 50% of their rated capacity, the smaller the discharge cycle, the longer the battery will last, therefore a battery of 30Ah would suffice. The UK receives on average 6 hours of sunlight per day during summer, which is the time of year we go camping, the main reason for building this system, therefore replacing 13.6Ah into a battery would take a 50W solar panel roughly 5 hours to recharge.
(Watts = Voltage x Amps)
(Average solar panel voltage at max power = 17 Volts)
(50 watts/17 volts = 2.94 Amps)
It's easier to draw power from a battery than to replace, requiring usually 10% more power to recharge than what was consumed, therefore:
(14Ah / 2.94 Amps = 4.76 hours of direct sunlight)
In a real world situation this will never happen due to too many different factors such as;
Solar panel shading,
Size of wiring,
Therefore it's safer to use a larger battery bank, where power can be used up repeatedly if weather conditions the day after aren't suitable for efficient solar charging to completely recharge the battery. My 225 amp hours is way overkill but it's better to have more power than required.
I already had my solar panels from my previous solar power supplies consisting of two AKT 80 Watt solar panels, one BP 80 Watt solar panel and four BP 12 Watt panels totalling a theoretical 290 watts. All of my panels were sourced from eBay over the years.