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

  1. #1

    Exclamation Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

    Peace guys,

    i am planning to built a system that can operate a 20 inch TV for 2hrs, a laptop for 2hrs, a fridge for 6hrs, a phone charger for 2hrs and say a 30W LED for 4hrs.

    i have 2x65W PV modules and a charge controller. i am confused about the battery. I think AGM batterys are good for this operation. Is a 50Ah battery a good option to go ahead with this system that i want to build? please advise experts
    Last edited by lionofallah; May 21st, 2013 at 23:55 PDT.

  2. #2

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

    Hi and good luck..

    It would help if you were a little more specific about the power consumption of your appliances but, I will suggest the following.

    You would need about 4x 80 watt panels and about 860 ah 12 v battery bank :)

  3. #3

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

    Quote Originally Posted by yrtrnc View Post
    Hi and good luck..

    It would help if you were a little more specific about the power consumption of your appliances but, I will suggest the following.

    You would need about 4x 80 watt panels and about 860 ah 12 v battery bank :)
    hey thankyou so much for your reply,

    well i am not specific on the ratings of my loads. we can base it on asumption. the ratings are usually general. well i cannot get any other panel other than the 2x65 watts. whats the best i can get out of this panels? 860ah sounds too expensive to me. basically i want to use this kit that i will make for camping. i hope that gives some better idea.
    Last edited by lionofallah; May 22nd, 2013 at 4:04 PDT.

  4. #4
    Join Date
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    Default Re: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

    Quote Originally Posted by lionofallah View Post
    hey thankyou so much for your reply,

    well i am not specific on the ratings of y load. we can base it on asumption. the ratings are usually general. well i cannot get any other panel other than the 2x65 watts. whats the best i can get out of this panel? 860ah sounds too expensive to me. basically i want to use this kit that i will make for camping. i hope that gives some better idea.
    Well, since we're dealing with a basic "assumption", we can assume that your panels, or proposed panels will give you a rough average of 265=13050%=654 hours full sun= 260 watt hours per day. What would that run? Perhaps your fridge for 2 hours, OR, perhaps your TV for 3 hours, OR perhaps your laptop for 5 hours, OR your 30 watt light for 8 hours. These of course are rough guesses, not knowing the exact consumption of each of your items, and also assuming your panels will have full sun at the right angle, and with no shadows for at least 4 hours a day, AND taking into consideration normal efficiency losses in such systems.
    AGM batteries, (for them to not die an early death) are not nearly as forgiving of abuse and improper charging etc as flooded deep cycle batteries, and are generally considerably more expensive, and for these reasons not usually recommended for anyone just learning about solar.
    1900 watts PV, (1000 watts PV feeding MidNite Classic 150; 900 watts PV + 160 watts micro hydro both feeding into a single shared Morningstar TS-MPPT-60) ; Xantrex Pure Sine 1800/12 for heavy loads; Xantrex Pure Sine 1000/12 on 24/7 for everything else; six Rolls Surrette 2 volt L16 @ 12 volts.
    Domestic hot water totally provided by the sun 8 months out of every year via thermal panel.

  5. #5

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

    Quote Originally Posted by lionofallah View Post
    Peace guys,

    i am planning to built a system that can operate a 20 inch TV for 2hrs, a laptop for 2hrs, a fridge for 6hrs, a phone charger for 2hrs and say a 30W LED for 4hrs.

    i have 2x65W PV modules and a charge controller. i am confused about the battery. I think AGM batterys are good for this operation. Is a 50Ah battery a good option to go ahead with this system that i want to build? please advise experts
    Welcome to the forum.
    AGM's and FLA's are interchangeable as far as providing raw power goes. AGM's are more expensive per Watt hour capacity, and require different charging parameters than FLA's. The main advantage they offer is; no gassing. This can be a concern if you plan on having the batteries in certain locations - like the livingroom.

    50 Amp hours @ 12 Volts does not produce much power: 300 Watt hours DC maximum. This definitely will not run a refrigerator for 6 hours, much less anything else on your list. A typical refrigerator will use 1.2 kW hours per day, and it is highly variable with the exact unit and conditions under which it is used. 30 Watts of LED lighting for 4 hours is 120 Watt hours alone. Plus you have to power the inverter which would supply the 120 VAC.

    Two 65 Watt solar panels would be able to charge about 75 Amp hours of battery, but again that is not enough to do what you are looking for.

    Before you buy anything else, buy a Kill-A-Watt meter and measure the power consumption of anything you want to run from solar. It is very important to know how much power you need to supply before trying to find a way to supply it.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

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

  6. #6
    Join Date
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    SF Bay Area (California)
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    Default Re: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

    I assume you are out of the Czech Republic, so you will need to find your local equivalent of one of these:

    http://www.amazon.co.uk/tag/kill-a-watt/products

    Solar/off grid power is not cheap--So you need to figure out your "real" energy usage...

    For a 20" TV, that can range from 11 watts to 100+ watts. And a laptop may run from 10 watts to over 60 watts (raw power of laptop, running, low power mode, recharging battery pack, etc.). A refrigerator may run around 130 Watts average power, but if frost free may take 600 watts for 10 minutes twice a day, and the compressor may run 15-30 minutes per hour so "average" over hours/days is less than the average running current, etc.).

    Power Labels on appliances are pure guess work--Some under estimate the load, and others way over estimate the loads (defferent between worst case/starting loads vs long term average).

    For example--A refrigerator running an average of 130 watts for 33% duty cycle by 24 hours per day:

    130 watts * 0.33 duty cycle * 24 hours per day = 1,030 WH = 1.03 kWH per day

    Refrigerators are one of the most difficult loads you will find on a small solar/off grid power system (very power hungry appliance). Another one can be a computer system.

    Many times, the appliances that run 24x7 (or a computer which may run 12 hours per day * 7 days per week) use more energy in 24 hours than a microwave oven (which maybe 1,500 watts but only 20 minutes usage per day).

    Also, you need to look at your loads... For example, a refrigerator/freezer, if kept closed during a power failure can go upwards of 24 hours without power before defrosting becomes a problem. There is almost no use to running a fridge for 6 hours on battery power.

    And, looking at your power needs... Is this for random power outages (such as during stormy weather) or do you have almost daily afternoon/evening power outages and need a battery system to ride through them. And want to add solar to reduce power bills a bit too...

    Many times, for random power outages a small/quiet/efficient generator is a better solution (if you have a property where you can safely store fuel and run a genset). A Honda eu2000i (1,600 watt genset) will run most of your basic needs on 1-2 gallons (2-8 liters) of gasoline/petrol per day (run generator maybe 12 hours per day for fridge and evening lights/recharge laptop usage). Get some fuel stabilizer and you can store the fuel for about 1 year (I recycle my backup fuel into my car every December). Get a multi-fuel camping stove, and you can live a pretty comfortable life during a few days of power outage (electricity, lights, cooking fuel). Get a couple of good quality LED flashlights + head lamps with common batteries for your region (AA Alkaline batteries are cheap here and will store for 3-5 years in a cool location) for backup/portable use/reducing generator usage.

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

  7. #7

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

    oh thank you so much guys. your replies were really helpful. not every forum has such positive comeback and no i am not from czech republic.

    however, we can get down the number of hours of the fridge. like i said earlier i am making a camping kit. so all i have is a 2x65W modules and i also have a charge controller. i am just confused about which battery to go for. since one of the moderators advised me i as a starter i should not go for it. now i am confused what battery to go for.

    so if we reduce the fridge to 2 hours, tv to 2 hours, 30W led lights for 4 hours, laptop for 2 hours and charging mobile phones. what chemistry of battery suites this operation and how many Ah battery would go with this? i was specifically calculating to fit inside a 30x30x30 cm aluminium case where I will install my battery, 12V dc Socket, a 12v usb socket and my charge controller.

    thank you guys and Bill, that was really really helpful!

  8. #8

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

    Worst case scenario: you work backward from the panels you've got. Get the largest battery they are likely to support (in this case you'll have about 7 Amps of peak current for a 12 Volt system so that's around 100 Amp hours) and when you run out of power you run out of power. Is there going to be any alternative charging source available such as a small generator or even a vehicle?

    Not the best way to do it, but sometimes you just have to work with what you've got.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

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

  9. #9
    Join Date
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    SF Bay Area (California)
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    Default Re: Solar Kit to run TV, Laptop, Fridge, Mobile or Lights

    I guess you are using a Proxy, so we cannot tell where you are from... We try to give answers that are, at least, regionally aware (line voltage/frequency, the amount of sun per day by season, local to you hardware suggestions)... So, for now, the generic answers.

    As Marc/Cariboocoot says, we can either design the system for the loads or design the system based on something you already have (solar panels, battery bank, etc.).

    Since you are "camping", then I would assume no Grid Power is available for charging during multi-day use.

    Your limit of 2x65 watt panels... That may be a lot of power for somebody truly camping--But for somebody setting up a remote office/lab, that is not very much power--So, your selection of what you want to operate is very critical to the success (or failure) of your off grid system choices.

    First, how much power can you get. For an off grid system that is running a smallish AC inverter (say 300 watts or less, on only on when needed), the assumed hours of noon-time equivalent sun per day can run from 4 hours (~9 months of the year for many places without heavy marine layer) to ~5-6+ hours of sun per day for Summer. During winter, 2-3 hours of sun is common for places closer to the poles (tropics, there is very little change for winter/summer sun unless it is weather related). In some places, less than 2 hours--And you may go days or longer with almost no useful sun (dark cloudy weather)...

    So, back to the estimates:
    • 2* 65 watt panels * 0.52 off grid system efficiency * 4 hours of sun per day = 270 Watt*Hours per day


    Yes--We are talking about ~50% in "losses" from solar array name plate ratings to useful AC power output...

    Now--that 130 watt refrigerator--About 2 hours of available power per day:
    • 270 Watt*Hours * 1/130 Watt load = 2.08 hours per day


    So, there is your daily power budget--~270 WH per day (typically early spring/late fall in clear weather--probably more in summer).

    Charging a battery bank... The typical rate of charge for a Lead Acid Battery bank is around 5% to 13% rate of charge:
    • 2* 65 Watt paneles * 0.77 panel+controller deratings * 1/0.05 rate of charge * 1/14.5 volts charging = 138 AH maximum battery @ 12 volts
    • 2* 65 Watt paneles * 0.77 panel+controller deratings * 1/0.10 rate of charge * 1/14.5 volts charging = 69 AH nominal battery @ 12 volts
    • 2* 65 Watt paneles * 0.77 panel+controller deratings * 1/0.13 rate of charge * 1/14.5 volts charging = 53 AH minimum battery @ 12 volts


    The 5% rate of charge is minimum recommended--And works best for a system that charges during the day and discharges at night.

    If you have a system that needs to produce power throughout the day, a 10% or higher rate of charge is better--Remember the loads during the day reduce charging current to the battery bank (which should be a minimum of 5% rate of charge).

    Your next problem is that you can only draw so much power from a battery bank before it is damaged/collapses... For example, the recommended sustained discharge rate for flooded cell is ~C/8 (20 hour capacity rate discharged over ~8 hour time period). And you should not discharge more than ~50% at a time for longer battery life (and never discharge below ~20% state of charge or it can ruin the battery bank). Using the 69 AH nominal battery bank as an example:
    • 69 AH * 1/8 hour discharge = ~8.6 amp discharge rate
    • 8.6 amps * 12 volts * 0.85 eff efficient inverter = 88 Watt average load
    • 69 AH * 0.50 recommended max discharge * 12 volt * 0.85 inverter eff = 352 Watt*Hour available storage


    Note, a 20 Hour Rate battery will appear to have less AH capacity if discharged at a C/8 rate.

    The maximum surge current from a Flooded Cell battery would be C/2.5:
    • 69 AH * 1/2.5 discharge = 27.6 amps max surge (seconds to minutes)
    • 27.6 Amps * 12 volts * 0.85 inverter eff = 281 Watts maximum surge


    Now, AGM (and GEL) batteries have some different parameters--For example AGM/GEL can support much higher discharge rates--So, if you have loads that needed high surge current but low average power, AGMs may be an interesting solution...

    Anyway, will stop here and see what questions you have.

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

  10. #10

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

    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! :)

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