DC to DC down converter recommendations.

tr0y
tr0y Solar Expert Posts: 99 ✭✭✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
As Solar seems to be a never ending addiction, and figuring out 12v is not a fun space to play in. I am planning at minimum a 24v upgrade. I have quite a bit of 12 gear and was wondering what if any brand or manufacturer of step down converter would be considered good. What are you using ? How many amps ? Looking for user experience with this type of device. Thanks 
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #2
    I believe Cotek has some...
     
    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
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #3
    Used a Samlex 24-12 30A years ago on a 24V Land cruiser for a stereo, worked well.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #4
    Also consider using a Morningstar MPPT controller (they are rated to work OK with a battery as a source) to downconvert battery voltage to float charge a 12V deep cycle battery, which should last a long time in Float service.  Figure what your average load is , and use a controller rated for 10, 15, 20 40 A as needed, to simply keep the battery in float.
    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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  • tr0y
    tr0y Solar Expert Posts: 99 ✭✭✭
    #5
    @mike95490 thanks for that idea, had not thought about just adding back another battery @ 12V and powering a controller with my 24v bank. None of this is cheap is it, but I think that might be a good idea. It also gives me a 2nd controller I can swap in and out if my primary Midnite Solar were to die. 

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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #6
    But not every MPPT controller can handle being connected to a stiff source like a battery.   Morningstar can.
    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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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    #7
    No doubts about Mike being right, but I'm curious how any MPPT charge controller design that does DC-DC could not work with a battery.  The input current is normally limited by the inductor and is cut off before it causes a problem.

    I am available for custom hardware/firmware development

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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #8
    Because many controllers are looking for a "soft" source like solar, or they shift the voltage point around to control the power, and you can't do that with a battery. 
    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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  • jonr
    jonr Solar Expert Posts: 1,386 ✭✭✭✭
    edited August 2018 #9
    So the MPPT algorithm discovers that the max power point is as much power as the controller can handle.   So what's the failure mode?

    Basically the same question pertains to MPPT controllers that list a maximum solar current input.   Something can't handle more, but it's not clear exactly what.

    I am available for custom hardware/firmware development

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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #10
    That assumes the controller can handle a non-solar over-power condition, not many can.   Feel free to get one and try it out,  I'm just posting what has been stated to work.  Likely most of the major players will be able to handle some amount of overpower.


    MS FAQ #3     http://support.morningstarcorp.com/faq/
    Using a DC power supply as a PV panel substitute?

    Morningstar PWM controllers are not designed to properly process input from a DC power supply. This type of input is not recommended and is connected at the user’s risk. DC power supplies have considerably more output capacitance than PV panels and connecting a DC power supply to a Morningstar PWM controller may cause excessive heating and premature failure.

    MPPT controllers can be used for this application with no issue.



    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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  • wankel7
    wankel7 Registered Users Posts: 18 ✭✭
    #11
    Victron has a huge range of DC DC converters
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  • Horsefly
    Horsefly Registered Users Posts: 476 ✭✭✭✭
    #12
    A also built a 24V system, but wanted to support several 12VDC loads.  I bought a Pyle 720W peak, 360W continuous 24VDC-to-12VDC converter. It's been working great.  

    https://www.amazon.com/Pyle-PSWNV720-Power-Converter-Technology/dp/B003P17X8I
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 8S (25.6V), 230Ah Eve LiFePO4 battery in a custom insulated and heated case.
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