How to Calculate Fuse Value ?

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • mmartell
    Badcaps Legend
    • Oct 2013
    • 3189
    • Canada
    #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 ?
    Tags: None
    • paulstef
      Badcaps Veteran
      • Dec 2013
      • 724
      • Canada
      #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

        • budm
          Badcaps Legend
          • Feb 2010
          • 40746
          • USA
          #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

            • mmartell
              Badcaps Legend
              • Oct 2013
              • 3189
              • Canada
              #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

                • mmartell
                  Badcaps Legend
                  • Oct 2013
                  • 3189
                  • Canada
                  #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.

                    Comment

                    Previous template Next

                    Related Topics

                    Collapse
                    • corrize
                      A funny fuse story – Lumix LX100 II
                      by corrize
                      Hello, I disassembled this dead camera, and found this WTF… Two fuses soldered one above the other !
                      I was pretty sure nobody touched it before, but that can't be from factory. There is flux, and capacitor is probably missing.
                      The other weird thing : the fuses are « G » fuse : (0.75A – 8V), seems very low. The original fuse should be « O » : (32V 2,5A).
                      There is « O » mark beside. All fuses have the same mark letter on main board. So, I can deduce it's a « O » fuse.
                      And this correspond to the issus I saw : when I plug the battery, I measure the voltage dropping...
                      10-19-2023, 09:58 AM
                    • jesterace
                      Samsung UE46ES8000 Blown fuse but no other signs of short
                      by jesterace
                      Hi I wonder if anyone might be able to steer me in the right direction. I have this Samsung UE46ES8000 TV and it went bang during use. The main fuse on the PSU board is open. I've checked every diode/mosfet/transistor I can see and nothing appears to be short to cause the fuse to go. The DC output of the bridge rectifier is not short either. I've seen online that some of these models are known for having their PFC mosfet or other mosfets shorting and blowing the fuse but i'm not seeing that here. If anyone aware of these models having any issues to cause this? I'm reluctant to just replace the...
                      09-11-2024, 03:14 PM
                    • jshhh
                      Help replacing fuse on my Mimaki CJV300-160 vinyl printer
                      by jshhh
                      Hi guys,

                      I'm inexperienced with electronics repairs, I've done a little bit of soldering caps and whatnot, but i have a blown fuse on this mimaki printer I got which I have bought a replacement for.

                      How do I remove this type of fuse (see picture)...it kinda looks like it would pull out of that bracket but it didn't come at first pull and I didn't want to brute force it incase it's soldered on there like most of the rest of the components.

                      Anybody know how to remove this type of fuse?

                      (The fuse is toward the bottom of the image labeled F2)...
                      06-17-2025, 01:35 AM
                    • Babbar
                      Argon SA1 audio amplifier power-supply - fuse blown after fixing the short?
                      by Babbar
                      I found a project in the electronics trash yesterday. A nice Argon SA1 audio amp with some electrical issue. Took it apart and saw that the 4A250V fuse was blown so started lifting components to find the short. Eventually got to two MOSFETs (model FTA14N50C) that are shorted and when i took them out the short was gone.

                      Now i didn't have any replacements of the same model of course but i found a couple with pretty similar spec i thought (K10A60D & K12A50D) and put them in. Also replaced the blown fuse with a 3.5A250V one. Checked another time for short circuit and plugged it in....
                      04-12-2024, 01:12 AM
                    • drykid
                      Matsui 175S microwave fuse replacement
                      by drykid
                      Hi,

                      I recently picked up a used Matsui 175S microwave that was powering up (starts, turntable rotates) but not heating. From looking online the most likely culprit was the fuse, but unfortunately in this one the fuse had heated up and fused with the (badly designed) fuse holder and couldn't be removed. I guess this might indicate further issues beyond the fuse itself but at this stage I just want to replace the fuse and see how I go from there.

                      Anyway since I couldn't get out the fuse itself the easiest fix was to replace the fuse holder assembly that runs between the...
                      12-21-2020, 01:15 PM
                    • Loading...
                    • No more items.
                    Working...