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Breaktru Forum  |  eCigarette Forum  |  Modding  |  Topic: Advice on PTC Fuse
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Offline kortt

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Advice on PTC Fuse
« on: November 15, 2012, 01:43:18 PM »
I want to sue a fuse in my mod but I haven't got a clue on what I should be using.

I am using the DNA12 module with an AW IMR 18650 2000mah (initially).  The PTC seems like a good choice to me, but don't know what specs I should be looking for as far as amperage etc.

Any advice?
Thanks!

Offline Dznutz

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Re: Advice on PTC Fuse
« Reply #1 on: November 15, 2012, 03:06:40 PM »

Offline kortt

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Re: Advice on PTC Fuse
« Reply #2 on: November 15, 2012, 03:17:09 PM »

Offline kortt

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Re: Advice on PTC Fuse
« Reply #3 on: November 15, 2012, 04:45:38 PM »
How important is the voltage rating for the PTC?  I wanted to steer away from surface mount if I can but the radial leaded PTC fuses I am finding are 3A with a 6A trip rated for 30V.  Would something like that be safe to use?

Online Breaktru

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Re: Advice on PTC Fuse
« Reply #4 on: November 15, 2012, 05:00:36 PM »
How important is the voltage rating for the PTC?  I wanted to steer away from surface mount if I can but the radial leaded PTC fuses I am finding are 3A with a 6A trip rated for 30V.  Would something like that be safe to use?

Something like this: 3A-PTC-FUSE

Offline kortt

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Re: Advice on PTC Fuse
« Reply #5 on: November 15, 2012, 06:09:14 PM »
Thanks for the help guys.  Placed my order for my PTC fuses.  Now waiting on supplies for my enclosure.

Offline CraigHB

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Re: Advice on PTC Fuse
« Reply #6 on: November 16, 2012, 03:35:25 PM »
How important is the voltage rating for the PTC?  I wanted to steer away from surface mount if I can but the radial leaded PTC fuses I am finding are 3A with a 6A trip rated for 30V.  Would something like that be safe to use?

The voltage rating indicates the voltage the fuse can tolerate when tripped.  PTC fuses don't actually open the circuit when they trip, they transition from very low resistance to a high enough resistance to drop voltage and current down to a low level.  Since there is still some current flow when they are tripped, they have to dissipate an amount of power.  The larger the package, the more power they can dissipate and the higher the voltage rating.

PTC fuses typically range from 6 to 60 Volts.  Since you're using a single cell and will not be going over 4.2V, you should be fine with one as low as 6V.  A higher voltage rating is fine if the part is preferable.

You want to pay attention to nominal fuse resistance.  You don't want it to be more than 30m Ohms since it can impact booster performance.  Running two of the 3A ones in parallel would be better since it cuts insertion resistance in half.  It also doubles the trip current, but it's still within tolerance of an IMR 18650.

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Re: Advice on PTC Fuse
« Reply #7 on: November 16, 2012, 04:45:14 PM »
Thanks for the info Craig, much appreciated.

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