MOSFET Caught on Fire. Help!

Discussion in 'Gun Building, Modifications & Repairs' started by Laserfish, Aug 16, 2012.

  1. Laserfish

    Laserfish Active Member

    1,055
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    Columbia
    Title pretty much says it. I plugged in a new battery and my HH AB MOSFET made a faint popping noise, started to catch fire, and released a large amount of heavy, acrid, gray smoke. What do I do?
     
  2. VTMZ

    VTMZ Active Member

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    Open the window and get a fire extinguisher
     

  3. Laserfish

    Laserfish Active Member

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    Columbia
    It went out after a minute when I unplugged the battery. Any ideas as to the cause or a solution?
     
  4. Laserfish

    Laserfish Active Member

    1,055
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    Columbia
    It's very hot and burned a hole pretty much right in the center.
     

    Attached Files:

  5. Mystery43_4

    Mystery43_4 New Member

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    HH? Never heard of them.

    Probably faulty design. That or you broke a wire/pin and it shorted.
     
  6. Fritz

    Fritz New Member

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    Camp Shelby
    ...Have you put out the fire yet?
     
  7. Laserfish

    Laserfish Active Member

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    Columbia
    Yeah, all good on the fire. The MOSFET isn't looking so good though. Recommendations for a new one?
     
  8. EDI1st

    EDI1st New Member

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    Fountain Valley
    HS5, Mystikal, Blake Buser etc etc
     
  9. alex

    alex New Member

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    did you plug in a dead battery? is that a polyfuse inside the shrink tube?
     
  10. Col1500

    Col1500 Member

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    Did you wire your battery backwards? I'm suspicious because it's a "new" battery. That'll cause stuff to explode just like that, unfortunately I know that from experience :(
     
  11. bsportft

    bsportft New Member

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    I'm sellinga basic bravo mosfet if you want it pm me. This is why I don't beak with this stuff anymore. I'd much rather run a lipo burn my trigger contacts and ruin my wiring than get a mosfet. It's just uneeded and if you know your way around a gearbox its a simple fix.
     
  12. Lefse

    Lefse Well-Known Member Supporting Member

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    A high quality mosfet won't burn out like that you know. If you have a good mosfet it will last for years even with a strong battery in a high drain setup, the trigger switch assembly can literally melt during a long full auto burst, it happened in my MP5K. I've made my mosfet units myself after the diagram they have over at Unconventional Airsoft, and they are 100% reliable.

    I have had this happen with cheap noname mosfets too. Bought two mosfet units from Airsoftpark, and they both fried after a few thousand rounds. That's why I decided to just build some mosfet units myself.
     
  13. alex

    alex New Member

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    refusing to learn is not a good way to live. with that attitude, i'm surprised you are using a LiPo. would you prefer to keep replacing pistons because you don't want to bother with adjusting AOE?

    why would you prefer to burn your trigger contacts because you fear mosfets? it is no more complex than soldering in a fuse.
     
  14. INFANTRYPRO

    INFANTRYPRO New Member

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    How do you build mosfets?
     
  15. alex

    alex New Member

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    Last edited: Aug 17, 2012
  16. Laserfish

    Laserfish Active Member

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    Columbia
    I don't think it was dead, but it may have been, why? Also, polyfuse?

    Today I tried removing the mosfet and just wiring it straight to see what happened but the entire gun got ridiculously hot in about half a second so I unplugged it. I suggestions?
     
  17. ld513

    ld513 New Member

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    Polyfuses are basically self resetting fuses with low resistance. Blue dragon makes some, extreme-fire have some built into their fets, I think D_E makes them as well.
     
  18. Lefse

    Lefse Well-Known Member Supporting Member

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    Polyfuses are awesomesauce. They are tiny, easy to add to your DIY mosfet unit and will prevent your gun from melting your face.
     
  19. alex

    alex New Member

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    cheap mosfets will fry when battery voltage drops to a certain level. if it has a polyfuse (cut the shrink wrap to see if it's a flat orange/tan square component). polyfuses protects the mosfets from shorts. if it's a poly fuse, then the mosfet fried from low voltage instead of shorts.
     
  20. Laserfish

    Laserfish Active Member

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    Columbia
    Took off the heat shrink. It was a polyfuse. So I assume then that I'll need a new MOSFET?