Fuse or breaker between bank and inverter?

cralls
cralls Registered Users Posts: 26 ✭✭
Hi All,

I just ordered a Magnum Energy MMS1012 Inverter and I have 4 - 232 amp 6V batteries run in series/parallel to make 12v - 464 amps. I'm looking at fuses and a lot of the 200 amp fuses are like $50 and then $16 per fuse to replace it if it blows. My question is, what would stop a guy from getting a "12V-24V DC HOME SOLAR SYSTEM WATERPROOF CIRCUIT BREAKER RESET FUSE INVERTER" off ebay for $13? 
:: 3 - Suniva OPT330-72-4-100 Silver Mono Solar Panels | Magnum Energy MMS1012
:: Midnite Solar Classic 200 | 4 - Interstate 6V GC2-XHD-UTL

Comments

  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    Hi cralls,

    Welcome to the Forum.

    Please check the manual for the 1012,  for advice on conductor size and breaker size recommendations.

    Circuit protection is sized for conductor size for the battery jumpers and cables to the inverter.

    You will really want a breaker,  and not only a fuse,  as the ability to switch the power OFF,  and ON to the inverter:
    http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/high-amperage-inverter-breakers/mnedc125.html

    The above breaker would need to be placed in an enclosure.

    Have not looked for the breaker that you noted in your post.

    Just be certain to choose cables sized to the Amp Rating of the breaker.

    Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • cralls
    cralls Registered Users Posts: 26 ✭✭
    Thanks for the response! My cables are 1/0 THHN on the bank and to the inverter. I definitely want to do a breaker as well, I just wasn't sure what the difference is between the car audio breakers that are 12V DC for $16 bucks and the solar ones for $50. I think that's really where my  hangup is. I'm also unsure about the size, the manual for the 1012 says max 300 amp so would it make sense to put a 300 amp fuse between the bank/inverter or does something smaller make more sense given I'm only running a 12v x 464amp bank? or does anything I'm saying make sense? haha
    :: 3 - Suniva OPT330-72-4-100 Silver Mono Solar Panels | Magnum Energy MMS1012
    :: Midnite Solar Classic 200 | 4 - Interstate 6V GC2-XHD-UTL
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭

    Hi cralls,

    1/0 THHN has an Ampacity of about 150 Amps.  So,  if you continue to run this size cable,  then the Overcurrent Protective Devices (Fuses or Breakers) should not be larger than this 150 A value.

    Some of the sizing of the cables and breakers,  also depends on the maximum Surge Current that the inverter needs to supply,  and the duration of these peak surges.

    Yes,  the real deal breakers might seem expensive,  but one of their main jobs is to open the circuit under Fault conditions.  A device that fails during one of these Faults,  could possibly cause a fire.

    Cannot pass judgment on the breaker from e-bay that you noted.

    FWIW,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • cralls
    cralls Registered Users Posts: 26 ✭✭
    edited March 2016 #5
    Hi Vic,

    Thanks much for the info, I really appreciate it! I looked up an ampacity chart and it looks like the particular wire I have is rated to 170 so I'll take your advice and go with a 150 breaker. I'm just going to spend the $50 on one made for solar applications because car audio equipment is probably different. There has to be a reason for the 300% price difference and I'm protecting a $1000 inverter, so the breaker is probably not the piece to try and go cheap on!
    :: 3 - Suniva OPT330-72-4-100 Silver Mono Solar Panels | Magnum Energy MMS1012
    :: Midnite Solar Classic 200 | 4 - Interstate 6V GC2-XHD-UTL
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    The circuit breaker does not "really" protect the device--Breakers are there to protect the wiring from overheating/catching fire if the device draws too much current (or the wiring is shorted, etc.).

    When you work with larger lead acid battery banks with multiple large/parallel battery strings--They can output somewhere close to 1,000 Amps, or more, into a dead short. The automotive breakers may not designed/rated to interrupt large fault currents (AIC -- Amps Interrupting Capacity).

    A better breaker will be rated for several 1,000 A to 10,000 AIC.

    Also, automotive breakers are rated for ~12 to 32 volts. The breaker family Vic pointed is rated for 125 VDC... For 24 and 48 volt battery systems, you have to check the operational voltage for the breaker/fuses.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • cralls
    cralls Registered Users Posts: 26 ✭✭
    Hi Bill,

    Thanks, that's a good point, I'm protecting the wiring and not the inverter!

    I am running at 12 volts, this setup is in an RV so I thought the automotive breaker might be ok since they are the same rating (12V DC 150 Amp) but there seems to be a huge price difference between the automotive ones and the solar ones so I just went with a solar one to be sure but I'm still curious what the difference would be. Since this is a smaller application I wasn't interested in a Din/Panel mount like Vic pointed out... I didn't even notice it was 125 VDC until you pointed that out. At any rate I ended up with this one: http://www.solar-electric.com/mrcb-150-amp-dc-circuit-breaker.html
    :: 3 - Suniva OPT330-72-4-100 Silver Mono Solar Panels | Magnum Energy MMS1012
    :: Midnite Solar Classic 200 | 4 - Interstate 6V GC2-XHD-UTL