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Thread: Battery to inverter fuse

  1. #1

    Default Battery to inverter fuse

    What size / type fuse do I need between my battery and inverter?

    12V battery bank (1 battery now)

    Samlex PST-150S-12A 1500w inverter

    I will have #4/0 AWG, 5 foot cable from bank to inverter...


    Thanks

  2. #2

    Default Re: Battery to inverter fuse

    Page 21 of the Samlex manual http://lib.store.yahoo.net/lib/wind-...50S-manual.pdf says a 300 Amp fuse is recommended. This is to accommodate maximum output power at minimum input Voltage (3000 Watts / 10.5 Volts).

    Five feet of 4/0 wire should have no trouble handling the current.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  3. #3

    Default Re: Battery to inverter fuse

    Thank you.

    I was looking on the Northern Arizona Wind and sun website for a suitable match and see a lot of them say #6 wire? I am a little confused as to which one to pick since I will have #4 wire? Which one will do the job?

  4. #4
    Join Date
    Feb 2009
    Location
    Michigan
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    72

    Default Re: Battery to inverter fuse

    Wonder how many amps one battery can put out safely? 300?
    5 Evergreen ESA 210's mounted, 4 Evergreen ESA 215's in the closet, Outback FM80, Xantrex Prosine 2, 4 Sunextender 8D batteries. 1 TLG wind generator. WB8ZMY Kirk

  5. #5

    Default Re: Battery to inverter fuse

    I will be adding more... I am just learning and would rather not screw up a whole bank. Once I have my system up the way I want I will put in a larger bank / panels.

  6. #6

    Default Re: Battery to inverter fuse

    Quote Originally Posted by sabud View Post
    Thank you.

    I was looking on the Northern Arizona Wind and sun website for a suitable match and see a lot of them say #6 wire? I am a little confused as to which one to pick since I will have #4 wire? Which one will do the job?
    Yes; you need to look at the right sort of holder. This one has 3/8" bolts that accept standard terminal lugs (crimped on to the wire): http://www.solar-electric.com/fb-300t.html

    A large enough battery will put out 300 Amps. But since that is the surge rating of this inverter most of the time the draw will be below 125 Amps. Probably well below that. This is one of the reasons why we do not recommend 12 Volt systems when the power needs are consistently above 1000 Watts.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  7. #7
    Join Date
    Jul 2007
    Location
    Quetico, Ontario
    Posts
    5,025

    Default Re: Battery to inverter fuse

    Look at the BlueSea fuses. Simple, easy to install and fool proof:

    http://bluesea.com/application/2/13/...e/overview/379

    Tony
    Please note, being a moderator does not add any weight to my opinions 300 watts Siemens/BP panels,plus a Sun 90,, making ~400. ~30 amps into Rogue MPT-3024, 450 ah of Trojan T-105, Morningstar ts300 inverter, a Tri-Metric meter.a collection of antique generators, plus 2 Honda eu-1000i's (also a BS2512 IX controller) and assorted other stuff!

  8. #8
    Join Date
    Mar 2006
    Location
    SF Bay Area (California)
    Posts
    21,364

    Default Re: Battery to inverter fuse

    At least, fool resistant (never proof).

    By the way, if you have flooded cell batteries, you should try to limit your continuous current to around C/8 (12.5%) of bank AH rating. (long term, can lead to overheating of batteries)

    And for surge current, keep to C/2.5 (40%) of bank AH rating. (battery bank voltage can collapse below 10.5 cutoff voltage for most inverters).

    Say you have 2x 6 volt 220 AH "golf cart" batteries for a 12 volt @ 220 AH capacity, the maximum Inverter AC output load recommendation would be:

    • 12 volts * 220 AH * 0.85 inverter eff * 1/8 max cont. current =280.5 watts max continuous (~8 hours or less to drain bank dead)
    • 12 volts * 220 AH * 0.85 inverter eff * 1/2.5 max cont. current =897.6 watts max surge

    Not written in stone... And if you have AGM batteries, you can draw a lot more current without problems. (also, if you are within 10-20% of above numbers, you are usually OK. Just carried all the decimal points so you can reproduce my math and make sure I am correct too. ).

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  9. #9
    Join Date
    Sep 2006
    Location
    Willits, CA
    Posts
    5,714

    Default Re: Battery to inverter fuse

    Just a note about wire gauges - so we are talking about the same thing

    #8 ga heavy wire

    #6 ga even heavier

    #4 ga heavier still

    #O Real heavy, pronounced "Single Ought" (Capital letter o)

    4/OOOO thumb size wire, pronounced "Four Ought"

    #4/0 does not exist, except as typo, 4/O does exist, as shorthand for 4/OOOO
    http://tinyurl.com/LMR-Solar
    http://tinyurl.com/LMR-BigLug
    http://tinyurl.com/LMR-NiFe

    Grundfos 10 SO5-9 with 3 wire Franklin motor (1/2hp 240V 1ph # 214505 ) on a timer for 3 hr noontime run - Runs off PV
    Powerfab poletop PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe battery | 15, Evergreen 205w "12V" PV | Midnight ePanel || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT

  10. #10
    Join Date
    Jun 2003
    Location
    pittsburgh, pa
    Posts
    10,282

    Default Re: Battery to inverter fuse

    for general speak if you had an infinite battery bank that could deliver the current you'd need for the inverter that you shouldn't have need of over 125a for a fuse/circuit breaker as 125a x 12v = 1500w. now if you find that you would be blowing this fuse or breaker that you would need to rethink your habits, your loads, your system, or all of the above. i, for one, don't like drawing more than 10% of my battery capacity on a steady basis and to draw steadily on a battery bank for a 1500w inverter would mean a battery bank in the area of 1250ah. do you plan to go that high in capacity? if you do plan to then you've got plans for the wrong system setup from the getgo as a 24v or 48v system voltage would suit better. odds are a smaller fuse/circuit breaker like 100a would be fine to use as this is representative of 1200w of power, but the final decision rests upon you.
    NIEL

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