SSR heating losses

grizzzmangrizzzman Posts: 18Registered Users ✭✭
What would be the best DC TO DC SSR amp rating to keep heating losses the lowest?( or any other method for that reason)
 Thanks
Boondocking is my game
640 Watts Mono Bogart TM2030 and SC2030  Controller GC 6V 208 AH  Costco batteries  300 Watt Inverter and 2000 watt inverter 2 GP 31 192 AH

Comments

  • mike95490mike95490 Posts: 7,916Solar Expert ✭✭✭✭
    There are Solid State Relays   SSR
    and there are DC-DC converters.     which are you asking about ?

    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 ,

  • BB.BB. Posts: 27,905Super Moderators, Administrators admin
    If you are talking about SSR's... There are a lot of fake/counterfeit versions out there:

    https://www.google.com/search?q=counterfeit+ssr

    Some of which are built well (and may even be just wrongly/falsely labeled) with smaller/lower current rated devices inside.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Posts: 2,212Solar Expert ✭✭✭✭✭
    edited January 2017 #4
    Solid state relays inherently generate heat and the larger the switched current, the more heat generated. Subsequently using a larger capacity rating for a smaller load will generate less heat, as it will not be running near it's limitations, but will still have losses. Using mechanical DC rated relays would be the best way to eliminate these losses at the expense of slower switching times. As suggested, use name brand SSR's such as Omron if you do decide on using them, beaware that fakes exist, best to purchase from a reputable distributor rather than unknown vendors. All too often, people go broke trying to save money,  on Ebay and the like.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • grizzzmangrizzzman Posts: 18Registered Users ✭✭
    edited September 2017 #5
    mcgivor said:
    Solid state relays inherently generate heat and the larger the switched current, the more heat generated. Subsequently using a larger capacity rating for a smaller load will generate less heat, as it will not be running near it's limitations, but will still have losses. Using mechanical DC rated relays would be the best way to eliminate these losses at the expense of slower switching times. As suggested, use name brand SSR's such as Omron if you do decide on using them, beaware that fakes exist, best to purchase from a reputable distributor rather than unknown vendors. All too often, people go broke trying to save money,  on Ebay and the like.


    So is the switching event causing the heat or a steady on or both?
    Thanks
    Boondocking is my game
    640 Watts Mono Bogart TM2030 and SC2030  Controller GC 6V 208 AH  Costco batteries  300 Watt Inverter and 2000 watt inverter 2 GP 31 192 AH
  • mike95490mike95490 Posts: 7,916Solar Expert ✭✭✭✭
    Both
    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 ,

  • BB.BB. Posts: 27,905Super Moderators, Administrators admin
    For solid state relays--It is probably mostly the level of current flow and the basic resistance of the device (I^2*R heating losses--current squared * resistance = Watts of heat) that is the heating effect (and possibly needing to mount the SSR on a good heat sink/metal surface).

    For high frequency switching, there is gate capacitance that lowers efficiency--But that usually does not apply here (very low frequency switching) where switching is occurring seconds to minutes to hours apart--Vs kHz to MHz of switching frequency. I.e.., there is little to no heat when low current is passed through SSRs, but lots of heat at high current (whether DC or AC current).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Posts: 1,079Solar Expert ✭✭✭✭
    Most efficient is a latching relay.   With a DC SSR, higher voltages help (ie, less power lost and heat at 48V than 12V for a given wattage).
  • grizzzmangrizzzman Posts: 18Registered Users ✭✭
    jonr said:
    Most efficient is a latching relay.   With a DC SSR, higher voltages help (ie, less power lost and heat at 48V than 12V for a given wattage).

    I considered a latching relay but I worry of burning contacts during the closing event. I am setting up two solar/battery systems that will tie together during high load events (inverter)
    Boondocking is my game
    640 Watts Mono Bogart TM2030 and SC2030  Controller GC 6V 208 AH  Costco batteries  300 Watt Inverter and 2000 watt inverter 2 GP 31 192 AH
  • mcgivormcgivor Posts: 2,212Solar Expert ✭✭✭✭✭
    edited October 2017 #10
    grizzzman said:
    jonr said:
    Most efficient is a latching relay.   With a DC SSR, higher voltages help (ie, less power lost and heat at 48V than 12V for a given wattage).

    I considered a latching relay but I worry of burning contacts during the closing event. I am setting up two solar/battery systems that will tie together during high load events (inverter)


    Use a DC rated contactor which is rated for the current, such as these  http://www.ametekswitch.com/products/dc-contactors-list
    Always use a contactor with  20% or higher rating, than actual current, SSR's have their place, holding high currents for extended periods is not one of them, short durations are fine.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 

  • jonrjonr Posts: 1,079Solar Expert ✭✭✭✭
    Agreed.  Use SSRs for short durations, lower currents (common with higher voltages), fast switching, lots of cycles.
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