DC to DC converters

monoloco
monoloco Solar Expert Posts: 103 ✭✭
in Off Grid Solar & Battery Systems #1
Does anyone have any experience in using a dc to dc converter to run 12v LED lighting off a 24v system
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  • rplarry
    rplarry Solar Expert Posts: 203 ✭✭
    #2
    Re: DC to DC converters

    Not for runing led lighting, but I used to have a boat that was 32v and I had converters to drop that votage to 12v. Had them for years with out any problems. Ran all my 12v equip such as radios, radar, sonar, etc.
    Larry
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: DC to DC converters

    how much led lighting do you have in mind as a converter may be overkill?
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  • john p
    john p Solar Expert Posts: 814 ✭✭✭
    #4
    Re: DC to DC converters

    I would be trying to run the LED lights in 2s in series. If it possible and it should be just arrange your LED lights so you have 2 on at any one time. This avoids have converter. Of course if you need run other 12v equipment this no use.
    24V TO 12V converters are usually no problem just be sure the unit is big enough for the load
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #5
    Re: DC to DC converters

    I built a batch of 48- 12V converters for a large LED lighting system, workes well, if you don't mind 10% loss from the downconversion
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • monoloco
    monoloco Solar Expert Posts: 103 ✭✭
    #6
    Re: DC to DC converters
    mike90045 wrote: »
    I built a batch of 48- 12V converters for a large LED lighting system, workes well, if you don't mind 10% loss from the downconversion
    Do you know how this compares with the efficiency of just running the standard ac to dc transformers that come with an mr16 type lighting system?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Re: DC to DC converters

    It is additional conversion steps. DC to AC to DC... However, if you have to send the power a "long distance" to the lamps--it may be worth the additional conversion to 120 VAC...

    My suggestion is to get a kill-a-watt meter and/or DC amp*hour/watt*hour meter and do your own testing (probably should have some sort of light meter too when working with LEDs).

    I don't really trust all of the advertising hype for energy efficiency... Many times the test conditions are different and/or they do not test to a repeatable standard (same power but different lumen outputs, etc.).

    Measuring directly will allow you to compare apples to apples, plus you will have the actual power measurements you can use to plan out your solar PV system / conservation measures for the long term.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #8
    Re: DC to DC converters

    Transformers are pretty darn efficient, about 95% or better if well made.

    DC-Dc converters are about 80-95%, but there is a specific load point where they reach 95%, but pull more or less load, and their effiency falls back to 80%
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #9
    Re: DC to DC converters

    When you talk about powering LED's you are talking about current sourcing.

    Using a voltage source you are forced to put a ballast to give the appearence of a current source to the LED. This is usually a resistor for DC voltage sources and is a source of significant power loss.

    The most efficient way to drive an LED is with an output current regulating DC-DC switcher. The output of the switcher is regulated based on current through the LED (or series of LED's) not voltage.

    There are switcher I.C.'s that do this specific job. There are LED electronic ballast available that package the entire circuit.
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  • monoloco
    monoloco Solar Expert Posts: 103 ✭✭
    #10
    Re: DC to DC converters

    Thanks for the input, I think I'm just going to go with the fixtures with built in transformers and run the lights off my inverter. It doesn't really seem like I'd be gaining anything by using a DC to DC converter.
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  • westyd1982
    westyd1982 Solar Expert Posts: 85 ✭✭
    #11
    Re: DC to DC converters

    A lot of newer LED bulbs have a built-in voltage converter (generally a buck driver) and can handle a wide range of voltages. I use a variety of bi-pin bulbs from superbrightleds.com that have a voltage range from 8-30 volts DC - no extra DC-DC conversion needed.
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