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Home Forums Technical Discussion Need Help – Solar Powered Fan

This topic contains 8 replies, has 5 voices, and was last updated by  j_pigden 8 years, 11 months ago.

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  • #36464

    tennispat33
    Member

    I am attempting to use two solar panels (both 4.5V 50mA linked to provide 9.0V) to power a small computer fan.

    The fan works like a dream when attached to a 9V battery (so this is clearly how much voltage I need) but when attached to the solar pannels it gives only a slight twitch.

    Is there a better way to attach the leads than electrical tape as this often melts and becomes mushy in the sun? Also, why are my panels not providing enough juice?

    Thanks for your help.

    #40318

    j_pigden
    Participant

    The problem isn’t voltage, it’s amperage!

    You wired the panels in series(4.5v * 2 = 9v) but 50mA. The muffin fans that I have need about .1A at full speed (40 panels in a parallel/serial array)!

    1. wire the panels in parallel (lower voltage but higher current) fan will turn slowly.

    2. switch to a rechargable 9v for occasional use & use the panels to recharge the battery.

    3. use solder connectors & large gauge wire to bring the power from the roof.

    #40323

    tennispat33
    Member

    I see, that makes sense

    it is a computer fan though (very small) so it might not need that much amperage?

    would a capacitor of some sort help with that?

    #40324

    j_pigden
    Participant

    1. Look for a ratings label on the fan housing on the motor body

    2. Try hooking the solar panels in parallel and see how the fan does

    3. Capacitors only store energy, you need to provide an energy source

    YOU NEED MORE PANELS

    #40325

    blueskymine
    Participant

    hello, I was reading through a site that seems to contradict wiring in a series… I am wondering what anyone thinks about the following:

    “ON BATTERY BANK INTERCONNECTION FOR OFF-GRID SELF SUFFICIENT LIVING DESIGN”

    “The novice often wires the parallel so that all positive terminals are connected, and all negative terminals, then taps off of one end or the other of the bank, thinking it will give him the amp hours we have indicated. I have even seen this type of connection diagrammed on solar sites that should know better. It will give the added amp hours, but it does so in the direction of the tap. The first battery goes down to 0% faster, then the next battery and so on. This causes the closest batteries to cycle and stay unused causing faster sulfation, wearing them out faster than the farthest. All of them will wear many times faster than they should, because it will be breaking the 50% rule.” http://wayoffgrid.com/

    I am a novice so please forgive me:), I just thought of this posting when I was reading this the other night, and started to wonder which is the best choice then…. have nice day

    #40328

    j_pigden
    Participant

    If you are talking about SLA (sealed lead-acid) batteries, then this is sort-of correct.

    Photo Voltaic Arrays (PVA) don’t behave the same way. They convert the energy in light into current flow. As long as there is light there is current flow. Batteries, on the other hand, convert a fixed amount of chemical energy into electrical energy. When the chemicals are gone so is the energy. If the energy draw is too much, the battery can suffer a pole-reversal from negative to positive. Rechargable batteries have the ability to convert the low potential energy chemical matrix into a high potential energy state through the addition of current. They have a limited number and range of this chemical reaction which sets the life of the battery.

    PVA’s don’t work this way. They take the energy from the sun and convert it into current flow. They don’t use chemical conversions and so, don’t suffer chemical breakdown like batteries. They are a source of energy to the battery array.

    Without any actual values, the words can sound scary but when the terms of the test are known, the claims lose their power.

    For this situation to occur, the battery chain must start fully charged, be used constantly until dead, then recharged fully, then used constantly until dead, ad infinitum. The real world is rarely like that. Every time the circuit is opened, the batteries create a gentle recharging effect that tends to even out the load to all the batteries. In addition, the recharging circuits in PVA’s control current flow to prevent overcharge and to deal with potential pole-reversal.

    A case of apples and oranges.

    #40329

    Anonymous

    In using ANY lead acid battery, you should never drain it any less than 20-25% of its amp hour rating..

    #40383

    12v man is correct, + if they aren’t deep cycle batteries you need to keep em probably above 80%. Learning about batteries is a needed must, they’re not all that simple sadly.

    #40411

    j_pigden
    Participant

    Excellent answers 12v & spontaneous; unfortunately neither answer has anything to do with the original question.

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