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Thread: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

  1. #11
    Join Date
    Mar 2006
    SF Bay Area (California)

    Default Re: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

    Your car battery is probably on the order of 80 AH at 12 volts = 960 Watt*Hours...

    A small generator running fairly efficiently will give you around 3,000 WH to near 6,000 WH per gallon of fuel.

    So--car sized deep cycle battery contains ~1/5th the amount of energy as a gallon of gasoline.

    Lead Acid (and really most any battery) does not store a lot of energy vs liquid fuels (gasoline, propane, diesel, etc.)... The advantage to a battery system is that it can be recharged with a solar array... To get ~5kWH from a solar array in decent sun (4 hours a day or more for 9+ months of the year):

    5,000 WH * 1/0.52 end to end system efficiency * 1/4 hour minimum sun per day = 2,403 Watt Solar Array Minimum

    So--if you want to have 5 days of emergency power @ 5 kWH of 120 VAC power per day (a pretty good sized amount of power)--You would need around 10x car sized deep cycle batteries + 2,403 Watts of solar array + AC Inverter + DC charge controller...

    Or a Honda eu1000i (900 watt) or eu2000i (1,600 watt) generator + 5-7 gallons of gasoline.

    Of course--The solar power system will continue to crank out power for 300+ days a year (excluding bad weather/deep winter). The genset would need another 1+ gallon of gasoline per day.

    This all gets back to your needs/loads... Small off grid solar power systems will only power small loads. Solar power is good where you need 9+ months of off grid power. A fuel powered genset is good for a few days of outages or weekend/seasonal cabin (with possibly a small battery+solar system for a few lights, radio, cell phone charger, etc.).

    Batteries start dieing the day they are made... They will last typically 3-7 years or so for golf cart type batteries in normal usage, or just sitting there in float charge... A generator will usually keep for a decade or more if properly stored. Gasoline/diesel will keep for ~1 year with fuel stabilizer (recycle to vehicle), propane will keep "forever".

    I highly suggest you look at your needs/loads first... Then start looking for hardware that can meet those needs. Typically "kits" are not as cost effective as DIY--But kits do have their place too.

    Just picking out random kits/hardware is probably not going to do much for you unless you are looking for something to charge your cell phone when camping...

    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  2. #12

    Default Re: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

    Quote Originally Posted by lionofallah View Post
    thank you Bill and cariboocoot, that Answered a lot of questions for me that i was having regarding my system.

    just wanted to ask you about this power unit by GoalZero, its called the 350 extreme and its 33Ah 12V and yes as the name says its a 350Wh battery. they are using an AGM battery inside. i checked with a friend and he has a 91Ah GEL battery and a 27-AGM trojan 91A battery.

    these battery is quite big and heavy. i was more interested in the battery used by goal zero in their product or may be a better battery than them. its much much smaller. their spec sheet does not speak about what brand of battery they used. any suggestions for a similar battery? this can be really helpful! :)
    Can't defeat the math: 33 Amp hours * 12 Volts = 396 Watt hours (what they call 350 Wh). At that point the battery is completely dead and probably won't recover. The real usable power would only be about 50% of the capacity: 16.5 Amp hours * 12 Volts = 198 Watt hours. Some of the power goes to run the inverter, which would be a MSW type that is not the best for running things like refrigerators.

    The Goal Zero (and similar) equipment as been discussed here before:

    Et cetera. As you can see, the claims companies make for equipment like this are based on the false premise that a battery's capacity is 100% usable and recoverable.

    Your friend's 91 Amp hour battery is almost 3X the capacity, which is why it is larger and heavier. It is also a much better choice if you want to get usable amounts of power (especially with two 65 Watt panels) If you haven't got the storage capacity, you haven't got the power.

    GEL batteries in general are not a good choice for RE because they are picky about their recharging specs; little room for tolerance in Voltage or current. AGM's may be a better choice for your application even though more expensive because they are lighter weight than FLA's.

    Some example batteries from our host just to give you an idea of what to look for:
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  3. #13

    Default Re: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

    hey bill, a big thanks to you for suggesting me that gen by honda, i actually own one already. the model number is Honda EM650Z. but i liked the one you showed me because its smalla nd compact.

    and Cariboocoot, thanks for the links on Goalzero and similar products, that was really helpful and I learnt alot. and thank you for suggesting some batterys. the amount of information on the thread is too damn high! ill be returning to refer your and Bill's calculations from time to time :)

    Thank you once again guys,

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