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Home Forums Technical Discussion what are the considerations in using a 12v and a 24v LED?

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This topic contains 4 replies, has 3 voices, and was last updated by  elnav 5 years, 2 months ago.

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  • #36878

    mdasb
    Participant

    I want to go for the system that will have less electrical consumption.

    we have a project that would use a lot of LED tape for cove lighting. The supplier has a 12v and a 24v version of a LED Tape.

    I figure, I go with the 24v model since it will have less current draw than a 12v model.

    Am I right in my assumption?

    If i had a system that has a total wattage of 100w, with a 12v system, I would only draw 8.33A whereas on a 24v system, it will draw 4.16A

    does this dictate electrical consumption? or just current draw?

    thanks

    #41643

    elnav
    Member

    My experience wih cove or strip lighting is that for a given illumination level the wattage consumed per foot comes out the same no matter what the voltage. The strip lighting designers will adjust things to give same lumens per foot regardless of supply voltage.

    However you are correct, a 24V system will have half as much current as the 12V system. Consequently the losses in the wiring will be a lot less with the 24V system.

    If you are running the cove lights from a battery. You should get longer run time with 24V before battery is depleted.

    Unfortunately another wrinkle is the battery capacity also comes into play. You need to double up on 12V batteries to get 24V. Since batteries only come in certain sizes you my end up with an amp hour ratting differeent from wht you exxpected. When series wiring 12V batteries to get 24V the amp hour capacity is the same while the voltage doubles.

    Parallel wiring the batterieis doubles the mp hour capacity but keeps the voltage the same.

    What may be a considerattion is how you are going to develop that 24V source. 24V chargers may be less common or available in your area or be quite a bit more expensive.

    #41656

    elnav
    Member

    The dollar stores are full of battery operated LED lights. Most require 3 cells meaning the nominal voltage is 4.5V Using a dropping resistor is terribly wasteful and definitely NOT energy efficient. I have noticed that a lot of cell phones have 4.5V charge adaptors. These are either the plug in wall cubes or a 12V DC plug adaptor for the car.

    These dollar store lights are very atractive price wise so the challenge is how to make use of them if your off grid dwelling is 12V.

    The one thing you do not want is to be using a large number of batteries when off grid. Its definitely pricy and the toxic waste is not conducive to our chosen lifesttyle with low environmental foot print.

    If you have a tiny home where wire losses for a 12V system is not going to be excessive one or two of these 12V adaptors may be enough. They have good conversion efficiencies much better than a dropping resistor and put out a voltage usable by the battery operated lights. Typical charging capacity on a cell phone battery is around 150mA whereas a typical LEd draws around 10 – 15mA so one adapttor will drive several LED lights. Be careful not to load it to the maximum or it will overheat and fail prematurely. Check temperatures frequently when first ussing the adapttor to drive LED lights.

    While its tempting to use very thin wires when wiring up LED

    My recommendationis still to use regular lamp cord. the larger diameter wire is more robust and will stand up to abuse, abrasion, and provide better mechanical protection than for example telephone cords which admittedly would work.

    A common battery voltage found in products is 6V. Be careful about simply plugging a 4.5V LED light into such a battery. The LED will be nice and bright becaause they are being over driven but they will fail prematurely.

    The good news is the ‘trikle’ charge solar panels you can find in automotive sections are nominally rated 12V but will serve to recharge the 6V battereies quickly. Just don’t leave then out therre all day. I have several 6V batteries salvaged from alarm systems and use my small 12V solar panels for recharging them.

    #42647

    JMill
    Participant

    mdasb,

    You are looking at electrical consumption, which is power measured in Watts. The total wattage of your system is the electrical consumption regardless of the voltage.

    Here is how it works:

    Power (watts) = Voltage (volts) x Current (amperes)

    100 W = 24 V X Current (I) –> I = 100 W / 24 V = 4.17A

    100 W = 12 V X Current (I) –> I = 100 w / 12 V = 8.33A

    The point is that you will be consuming the same amount of power on either the 12V or the 24V system. So to reduce your consumption, reduce the total wattage.

    #42670

    elnav
    Member

    More to the point because power is current squared then multiplied by resistance, if you use same size wire the wire resistance losses will be one quarter as much at the higher voltage. This is significant if you are building a minimal system with limited power capacity or trying to pull maximum power thru marginal wire size.

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