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How to Calculate Fuse Value ?

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    #1

    How to Calculate Fuse Value ?

    Wasn't sure where to put this...

    I have battery charger for a small lead-acid battery that is rated at 12v/1.0a for which a mosfet blew up and destroyed the small diode-looking fuse. I've made the necessary repairs but am at a loss for what value fuse to replace the old one with.

    Is it safe to put in a 1.25a fuse (a little more than the rated amperage output) or is it more complex than that ?
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    #2
    Re: How to Calculate Fuse Value ?

    If it's rated 1A it should probably limit the charging current to 1A. So it seems that a 1.25A could be suitable.

    If it was me I would probably monitor the current on an empty battery and then decide the fuse value.

    Why did the MOSFET blow up? Is there maybe more to it? Does the current limiting not work maybe?

    Comment

      #3
      Re: How to Calculate Fuse Value ?

      It can be really complicated, just read these tech info.
      You can try 1.25A for now since you do not have all the data such as as the surge current, the length of the surge, etc.
      Attached Files
      Never stop learning
      Basic LCD TV and Monitor troubleshooting guides.
      http://www.badcaps.net/forum/showthr...956#post305956

      Voltage Regulator (LDO) testing:
      http://www.badcaps.net/forum/showthr...999#post300999

      Inverter testing using old CFL:
      http://www.badcaps.net/forum/showthr...er+testing+cfl

      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
      http://s807.photobucket.com/user/budm/library/

      TV Factory reset codes listing:
      http://www.badcaps.net/forum/showthread.php?t=24809

      Comment

        #4
        Re: How to Calculate Fuse Value ?

        Nah what happened was the output cable became frayed at the strain relief (thanks for nothing, strain relief!) so I took it apart to fix that. My guess is during the time I man-handled it I moved the heatsink for said mosfet enough that I made trouble with the shitty solder joints under it and when I powered it on, poof! It's repaired now and appears well under no load with a small piece of wire used as a temp fuse. Want to put a proper fuse in before hooking to battery for a load test.

        Comment

          #5
          Re: How to Calculate Fuse Value ?

          I did read a little b4 posting and so suspected it could get complicated. Thanks for the links.

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