*Battery Question*

Competed
Competed Registered Users Posts: 3
in Solar Beginners Corner #1
If I have a 7.4, 1100mAh 15c battery and I am using LEDs that draw 1 watt consistently how long will the battery last? I recently purchased a LED module and it says on the site "Once pluged with battery, LED module will start consume battery (1 watt.) You have to unplug the battery to turn it off." So I am just wondering how long this will last if it was just left on all day.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #2
    Re: *Battery Question*

    I assume that 7.4 is voltage and hence they're li-ion 1.1AH batteries. Li-ion will sycle from 20 to 90% of SoC, so 70% must be useable, which gives you 0.77AH. 0.77AH*7.4W = 5.7WH. If your LED is 90% efficient (wild guess), it consumes 1/0.9 = 1.1W, so it'll last 5.7WH/1.1W = 5.1H. So, you should expect it to last for 5 hours. The best way, however, is to check this by experiment. Plug it in and time how long it lasts.
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  • Competed
    Competed Registered Users Posts: 3
    #3
    Re: *Battery Question*

    What about a Lipo 1300mAh 11.1v 15c?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: *Battery Question*

    Welcome to the forum.

    Are we talking about a 7.4 Volt 1.1 Amp hour battery? Are the LED's also 7.4 Volt? If so you are looking at approximately a 135mA draw. If this were linear (and it isn't) that would bring the battery down to 50% in approximately 4 hours. But as the Voltage goes down the current goes up which not only increases the rate of discharge but also decreases the effective capacity of the battery.

    As the Voltage goes down the LED's will dim, so you also have to consider what is an acceptable level of brightness and acceptable level of discharge for the battery. So don't expect more than 4 hours, and try it to see where you are comfortable with the declining output.
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  • Competed
    Competed Registered Users Posts: 3
    #5
    Re: *Battery Question*

    Here's the battery: http://www.amazon.com/Raptors-Airsoft-Lipo-1100mah-Battery/dp/B00BBKOHSE

    Specs:
    Capacity: 1100mAh
    Voltage: 7.4V
    15c

    And here's the LED module: http://madbull.com/catalog/index.php?main_page=product_info&products_id=254

    Specs:
    Voltage: 7.5-12.6v
    Life 10000+ hrs
    1 Watt
    8 Blue SMD LED (O.C.)
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: *Battery Question*

    The LED's will be running on the low end (actually under, but batteries are a bit higher than rated Voltage) of their Voltage range to begin with. You probably will not be happy with the performance.
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