Battery to inverter fuse

sabudsabud Posts: 12Registered Users
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

Comments

  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Battery to inverter fuse

    Page 21 of the Samlex manual http://lib.store.yahoo.net/lib/wind-sun/PST-150S-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.
  • sabudsabud Posts: 12Registered Users
    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?
  • snuffysnuffy Posts: 72Solar Expert ✭✭✭✭
    Re: Battery to inverter fuse

    Wonder how many amps one battery can put out safely? 300?
  • sabudsabud Posts: 12Registered Users
    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.
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Battery to inverter fuse
    sabud wrote: »
    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.
  • icarusicarus Posts: 5,070Super Moderators admin
    Re: Battery to inverter fuse

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

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

    Tony
  • BB.BB. Posts: 24,570Super Moderators admin
    Re: Battery to inverter fuse

    At least, fool resistant (never proof). :roll:;)

    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. :roll:).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Posts: 6,298Solar Expert ✭✭✭✭
    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
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  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    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.
  • john pjohn p Posts: 814Solar Expert ✭✭
    Re: Battery to inverter fuse

    A 100a fuse would be adequate, And if that blows you are overyloading the battery anyway. As you have been told one battery unless its about 800ahr wont take kindly to a continuous draw above about 60a.
    A100a fuse will withstand an overload of 20a if less than 2 seconds.
  • TobitTobit Posts: 41Solar Expert
    Re: Battery to inverter fuse

    Sorry to bump an old thread but I have a related question more towards type of fuse between the battery and inverter, fast acting or slow blow? The inverter manual I'm reading only states 80A with #4 gauge wire. Thanks.
  • CariboocootCariboocoot Posts: 17,615Banned
    Re: Battery to inverter fuse

    Inverter fuses: http://www.solar-electric.com/infubr.html

    Breakers are even better.

    On the whole you want slow-blow here as a sudden surge load (can be 2X inverter's running current) may pop a fast-acting fuse.
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