Page 1 of 2 12 LastLast
Results 1 to 10 of 12

Thread: What size fuse should I connect to the battery? If needed at all..

  1. #1
    Newbie
    Join Date
    Mar 2011
    Posts
    4

    What size fuse should I connect to the battery? If needed at all..

    Hello, just looking for some some advice really.

    I've recently bought a 1800W Sub with built in amp, all enclosed with it's own fuse. I'm connecting 2x 375W speakers to it. Do I still need to fuse at the battery to protect anything major? Such as the speakers? Or will the built-in fuse be sufficient?

    If so, what size fuse do I need? (375 + 375 + 1800) / 12 = 212.5 amps?

    Cheers.
    Last edited by Shallice; 03-13-2011 at 08:35 AM.

  2. #2
    Constant Bitrate knownchild's Avatar
    Join Date
    Dec 2010
    Location
    IOWA
    Posts
    141
    The built in fuse is to protect the equipment and the fuse by the battery is to protect your wiring, if you don't protect your wiring you could damage your cord and even worse start a car fire.

    I would look to see what size of fuse is already on your equipment and put the same size fuse at the battery.

    Also you might find this CALCULATOR helpful!!
    Last edited by knownchild; 03-04-2011 at 08:30 AM.
    Never accept STOCK equipment.

  3. #3
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    Location
    on the border of northern IL/IN
    Posts
    5,848
    what he said.

    the whole reason is a extra layer of protection-- if you car gets split in half in a horrifying wreck, the last thing you want is a cut power wire shorting out, and catches the gas tank on fire... the fuse at the battery would prevent that(the fuse would blow as soon as the power wire got sheared)..

    the IASCA rule is less then 18" from the battery, but i always say to keep it less then 12"...

  4. #4
    Newbie
    Join Date
    Mar 2011
    Posts
    4
    Thanks for your help, I got everything fitted but I just can't get the main cable from the battery to the boot. I don't really want to drill through the dashboard..
    Last edited by Shallice; 03-06-2011 at 04:24 PM.

  5. #5
    Newbie
    Join Date
    Mar 2011
    Posts
    4
    Got it done and the battery died.

  6. #6
    Low Bitrate
    Join Date
    Feb 2005
    Location
    Cali
    Posts
    111
    Good job on the wiring. You generally don't have to drill through the dash, as there should be some wires coming through the firewall from the engine compartment already. So next time, just share that opening.

    As said before, the fuse at the battery is to protect the wiring and stop a fire, not protect the equipment. The size of the fuse is dependent on the gauge (size) of the power wire, not the draw of the electronics being powered. Higher power electronics draw more current, so require a larger wire to supply, and therefore a larger fuse. Use the calculator above to ensure you used correct size power wire. You can always use larger wire to run the power (say 2-4 gauge), with a little signal loss and greater expense. Overfused smaller wires may draw too much current to handle, overheat, melt the insulation, and either short to a ground and blow the fuse, or in the worse case, cause a fire.

    The battery dying is indicative of the amp not shutting off with the ignition, an inadequate charging system, bad battery, or a leak (short) to ground.

    Good luck...

  7. #7
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    Location
    on the border of northern IL/IN
    Posts
    5,848
    Quote Originally Posted by Thefdog View Post
    As said before, the fuse at the battery is to protect the wiring and stop a fire, not protect the equipment. The size of the fuse is dependent on the gauge (size) of the power wire, not the draw of the electronics being powered. Higher power electronics draw more current, so require a larger wire to supply, and therefore a larger fuse. Use the calculator above to ensure you used correct size power wire. You can always use larger wire to run the power (say 2-4 gauge), with a little signal loss and greater expense. Overfused smaller wires may draw too much current to handle, overheat, melt the insulation, and either short to a ground and blow the fuse, or in the worse case, cause a fire.
    to a extent, your correct.. i get what you're saying, but had to re-read it a couple of times to understand it.

    recap:

    you always fuse for the end-load, this way any substantial draw will blow the fuse and protect the wire.

    as a example-- i tend to run wires that are way too large for their intended purpose. my carpc has a 8ga wire run to it-- according to my brief search, 8 ga wire is rated for about 45-50A maximum draw. my carpc power supply has a 20 amp fuse.. so i installed a 20A fuse on the wire. this way, if something went wrong with the carpc, i might blow 2 fuses instead of one, but i protect everything.

  8. #8
    Constant Bitrate knownchild's Avatar
    Join Date
    Dec 2010
    Location
    IOWA
    Posts
    141
    Exactly, trust soundman he is 100% correct.

    By the way could somebody give me +rep cuz when i got negative it was when i was being a noob LOL
    Never accept STOCK equipment.

  9. #9
    MySQL Error soundman98's Avatar
    Join Date
    Jan 2008
    Location
    on the border of northern IL/IN
    Posts
    5,848
    ya gotta earn it!!

    but really, i don't pay attention to the e-rep stuff... i think it is always important to remember that some people know a lot on certain topics, others know a lot about other topics, and all of them are usually misinformed on the rest...

  10. #10
    Raw Wave
    Join Date
    Nov 2009
    Posts
    2,119
    If it's a really fat wire, it could run under the vehicle - but must be well protected, some use conduit or garden hose etc - but NEVER without a fuse!!!

    1800W (+700W) suggests a 250A fuse (divide by 10 rule), but that assumes an RMS rating.
    If it is 1800W RMS, its own fuses will exceed 150A.



    Quote Originally Posted by soundman98 View Post
    you always fuse for the end-load.... (this way any substantial draw will blow the fuse and protect the wire).
    [I added the (parentheses).]

    I too want to support Soundman's advice. Too many follow the "fuse for the wire" doctrine.

    Sure, the fuse size cannot exceed the capability of the downstream cable. (Otherwise the cable will fuse instead of the fuse, hence a likely fire etc.)
    But that does NOT mean it cannot be smaller.


    I too often do as soundman98 and use much heavier wire/cable than is required. (Why? Less voltage drop. Future expansion.)
    But then I will fuse for the load - especially if using 400A cable for a 10A load (compare the fuse or circuit breaker prices and see. (And not that reducing cable for a fuse seems normal or easy, but it is a valid practice.)

Page 1 of 2 12 LastLast

Similar Threads

  1. What size in line fuse needed
    By jay88907 in forum Car Audio
    Replies: 3
    Last Post: 01-07-2009, 06:20 PM
  2. Fuse size by battery
    By TeamRSX in forum Car Audio
    Replies: 3
    Last Post: 05-07-2008, 09:28 AM
  3. Replies: 4
    Last Post: 07-19-2006, 06:57 PM
  4. Opus 120, 12V line from battery, what size fuse?
    By 01black_ac in forum Power Supplies
    Replies: 21
    Last Post: 04-11-2006, 11:53 PM
  5. What size fuse should I use at the battery?
    By EpRiDaZ in forum General MP3Car Discussion
    Replies: 13
    Last Post: 01-26-2006, 12:41 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •