48v to 12v step down converter?

midijeep
midijeep Registered Users Posts: 102 ✭✭✭
edited July 2016 in Solar Beginners Corner #1
I want to run directly  off my 48v battery bank , four 12v LED lights.  I will put a load center with breakers between the battery bank and lights.  The wiring coming off the load center is 10 gauge wiring, which is going to each of the lights. 
I am in need of some advice to step down the voltage from 48v to 12v.
I am looking at these two converters and a  load center panel:

Load center panel
http://www.backwoodssolar.com/six-circuit-load-center-kit

and

Dc to Dc converter #1
http://www.ebay.com/itm/like/391501899600?lpid=82&chn=ps&ul_noapp=true

and

Dc to Dc converter #2
http://www.backwoodssolar.com/ppt12-48-10-r12-step-down-converter

Do you have any recommendations or advice?

Thanks
Bj


Comments

  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    the Golf Cart DC Converter 48V to 12V Step Down VOLTAGE 20 A
    likely has too much overhead and no attention to efficiency
    The backwoods model is way too expensive

    What is the amp load of your LED lights when all are turned on ?   You only need a DC-DC converter that can supply 130% of that
    here's a site with a lot of choices
    http://www.digikey.com   search for DC-DC and they have 10,000's of them  Narrow down the values you need.


    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 ,

  • midijeep
    midijeep Registered Users Posts: 102 ✭✭✭
    Total amps with all led lights on will be 5 amps at 12v
  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    Be sure that it can handle the maximum voltage that your bank will ever see (when equalizing).  Ie, much more than 48V.  I'd get one speced for 10A - this should provide good heat dissipation and be close to peak efficiency.

    I am available for custom hardware/firmware development

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Are you going to have point-of-use converters , using 48V to the point of use or are you going to down convert and send 12 V to point of use? The latter is far less efficient in wire losses than 48V...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • midijeep
    midijeep Registered Users Posts: 102 ✭✭✭
    Are you going to have point-of-use converters , using 48V to the point of use or are you going to down convert and send 12 V to point of use? The latter is far less efficient in wire losses than 48V...
    I'm not sure?  How would you wire/put together the more efficient method?
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    edited July 2016 #7
    you 'send' 48 volts to all points of use and then change to 12 volts , but remember that you will have add:  PV in  voltages up into the 80+ volts range! during Absorb  and EQ times.  add:  And that the Cc will output to the max V set for these stages , which can upset your inverter or  whatever that is  a '48 V' device.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • oil pan 4
    oil pan 4 Solar Expert Posts: 767 ✭✭✭✭
    edited July 2016 #8
    Holey crap. I thought 48v banks only equalized at like 64v max.

    The simplest cheapest thing I can think of is wire each light to a 12v battery. Just make sure you turn them all on and off at the same time.

    This is one of the draw backs of 48v, not much is made to directly run off 48v.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Is the 48 volt system driving some other (much larger) loads?

    Will you have 120 or 240 VAC voltage available (i.e., an AC inverter that is already running 24x7)?

    If so, perhaps you would just wire out the AC power to the LEDs point of usage--And use AC rated LEDs? Can be cheaper for 120/240 VAC LED bulbs, and it is much cheaper/easier to run your AC power much longer distances with much smaller AWG wiring.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • midijeep
    midijeep Registered Users Posts: 102 ✭✭✭
    edited July 2016 #10
    For my setup I have:

    Grid-tied System with battery backup (48v bank)
    SMA SunnyBoy 3000TL-US-22
    SMA Sunny Island 6048
    Midnite Solar E-Panel
    Midnite Solae Autoformer (gives me the 240v)
    48v Battery bank

    The room is already wire with AC lighting but when that goes down I want to have the DC lighting to take over by running them directly off the 48v battery bank.  All the solar equipment is in this room. From what I understand using the SMA equipment, I have no choice in what voltage to run the battery bank. It has to be 48volts.

    I would like to place a DC loads center between the 48v battery bank and 12v LED lights for safety and maintenance.

    There will be no other loads on the 48vDC to 12v DC other than the LED lights.

  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    I had some small 12v loads (routers, ooma and a laptop) and I ended up using an old 12v battery and a morningstar charge controller (rated for 6 amps I believe) I had sitting around.  Then I just connected the charge controller to the 48v bank (on the solar input) and the other side to the small 12v battery and let it do it's thing.  The nice part was the small 12v battery acted as buffer and an additional backup beyond the inverter.

    But I ultimately changed to what Bill suggested and went to 120vac to 12vdc route and just used the inverter to power the loads, less work, less wiring, less battery to maintain, but it was redundant backup.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited July 2016 #12
    > The simplest cheapest thing I can think of is wire each light to a 12v battery. Just make sure you turn them all on and off at the same time.

    Or if "all on" is too inconvenient, buy a series battery bank equalizer (about $55 for 4x12V batteries).  Cheaper than some DC-DC converters (and probably beneficial even without uneven current loads).

    Yet another option is to look closely at the LED drive circuit.  They are current controlled, so if the components can tolerate 48V (nominal), it won't hurt the LED.  Even a LED driver designed for 120VAC might run fine on 48V DC (it's typically rectified then buck converted).

    I am available for custom hardware/firmware development

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Made an addition to clarify my  previous post, sorry for any confusion.
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • midijeep
    midijeep Registered Users Posts: 102 ✭✭✭
    I found some 48v LED lights.  Instead of stepping the DC voltage down from 48v to 12v to power the lights, would coming directly from the 48v battery bank to the DC load center, then to the 48V lights be a better option?
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    That would probably be the most efficient way to do it.  Now you will need CB's , switches etc to handle  48 Volts or higher..
    .
    Are those LED's able to handle the Absorb and EQ voltages if they were turned on during those charge phases?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • vince
    vince Registered Users Posts: 79 ✭✭
    I am running some several dc-dc (10A) converters to run 12 and 24 V lights, pumps and appliances from my 48V bank. No problems handling the 60V max. and the output of the converter is very stable regardless of the input which may range from 49 to 58V.
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • midijeep
    midijeep Registered Users Posts: 102 ✭✭✭
    Could you give the make/model of the converter you are using?

    vince said:
    I am running some several dc-dc (10A) converters to run 12 and 24 V lights, pumps and appliances from my 48V bank. No problems handling the 60V max. and the output of the converter is very stable regardless of the input which may range from 49 to 58V.

  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    Interesting, I took a standard 120VAC Cree LED lightbulb and applied 30VDC and it worked fine.

    I am available for custom hardware/firmware development

  • vince
    vince Registered Users Posts: 79 ✭✭
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.
  • midijeep
    midijeep Registered Users Posts: 102 ✭✭✭
  • vince
    vince Registered Users Posts: 79 ✭✭
    No, the transformers have build in protection and the wiring could handle the load
    Sunpower 3 x 435 watt panels, 48 v 215 AH battery bank (Sam's club), Midnite Kid and WBjr, Fujitsu 9RLS3 split duct AC, Outback FX 3048T + transformer 2000W 120/220V, GrapeSolar Fridge.