by 8ball_99 » Thu Aug 09, 2012 12:55 pm
Well my panels came from solarblvd.com.. They are 80 watts each and are 12v.. Here is the problem.. Our wonderful goverment just passed a solar tariff.. Pretty much they stuck a 30% tax on a lot of the panels being shipped in to the us. So cheap panels have gotten hard to come by... I paid like 105 each for my panels.. I tried to buy two more right around the time the tariff went into effect and they could not get them. Still to this day they don't have them in stock.. They do have the 100 watters for 145 now. If I wouldn't had already built my rack to hold 4 of the 80 watters I'd probably get the 100s.. I'm miles away from being a solar expert. But the power part of it isn't to hard to understand.. If you want to run that 200 watt fridge you would need a lot of solar and two batteries.. Since you don't have the fridge you would be much better off just buying a 12v fridge that only uses a couple amps of power.. The fridge would cost a little more but your solar needs would be much less. so would the battery reserve.. So it would cost you less in the long run to just buy a better fridge. Inverters are great to run something small for a few hours or something big for a short time.. But trying to run an appliance 24/7 on something that pulls a couple hundred watts is not ideal.
The panels you have are not that bad.. Infact I have 4 of them myself I bought a few years ago.. You can get better panels that put out more power for about the same money though. Two of those 15 watt panels pretty much equal a trickle charger. Thats just a couple amps. They are good to keep a battery topped off while the trailer is in storage or maybe to extend the period between charges but not really enough power to run very much. Just a fantastic fan on low pulls almost 2 amps. Infact when I put solar on my trailer I figured one 80 watt panel would pretty much offset our two fans running. The other panel was to put back the power used running lights, radio, ect. The only real way to go about solar is to figure out your usage. How much power you use on average and then figure watt panels and what batteries you need.. Post that and we can crunch the numbers!
Just for example if you did want to run that 200 watt fridge on an inverter and only use solar for power. That fridge over 24 hours would use about 120 amp hours. That puts your solar needs at around 3 100 watt panels.. The way you figure it is a 100 watt panel at 12v puts out around 8 amps.. You times that by the amount of daylight.. Say 7 hours. So that one panel is good for about 56 amp hours. So three 100 watt panels in a perfect world would give you about 168 amp hours a day.. So with the losses from the inverter, wire, battery and if the fridge only runs half the time that should be about right just to run the fridge.. You would also have to have two batteries since over night that fridge would pull around 60-70 amp hours which would kill a single 110 amp hour battery pretty quick since your pulling it down below 50%.
A good 12v compressor fridge will use 2-3 amps when running compared to the 10amps of that dorm fridge.. So that would knock down that 120amp hours needed to about 36 amp hours.. That puts you down to one panel and one battery. That alone is what 400 bucks difference in the cost of the solar setup..
