Need some advice with building my 3P unreg box mod

[Hell_Vapor]

So I'm building an unregulated triple parallel 18650 box mod. Now the main reason I'm building this is so I can use my super low ohm coil builds with more peace of mind.
I plan to use this mosfet
http://www.mouser.com/Search/m_Prod...hyDBzk1/Wi5vIKI30lxcJdx0By8b2zMOiHC3hqtgzPw==
Now here's what I need advice with. With a triple parallel box I get 3x the app limit that I get from a single battery. So I have LG HD2C's which are 35a continuous, 50 amp pulse. So 50*3= 150 am pulse for my mod. But say one of the batteries fail or fails to make contact for whatever reason, and without knowing it I'm vaping on two working cells. Now that draws 75 amps per cell which is no bueno.
So to prevent that from happening I want to use 3x 50 amp fuses, one per battery cell. This would trip all the fuses if one battery failed. The problem is I can't find any 50 amp PTC resettable fuses anywhere, not sure if they even exist. And I found this fuse and some others similar to it, but I can't find much information about them or data sheet or anything.
Blue Sea Systems 40588 5252 MIDI/AMI Fuse 50 Amp at 3tailer.com
And adding three high amp fuses like that impede the power of my device too much? I mean I don't want an insane amount of voltage drop either you know?
Any advice is greatly appreciated
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[K3nn0Q]

You could try parallel PTC fuses on each battery
That's an impressive little MOSFET, but it'll probably need a heatsink above about 40A... but you could parallel a couple of those as well

 

[Hell_Vapor]

Thanks, I really took my time to find a good mosfet. I really like this one for its super low Rds(th). Haven't done the math yet to see if it needs a heat sink or not. As far as the fuses, I might be able to find 20A PTC fuses but I would need 6 of them 2 to each battery, giving me a 120A limit for my device. Or if I couldn't find 20A then could I use 3x 15A fuses per battery?Does that sound crazy to have that many fuses? And how bad would something like that effect my Voltage drop?

 

[K3nn0Q]

It's got a decent Rds(on), but there are some sub-milliohm ones out there (it's 1.8~2.2mΩ @ 4.5V the IRLB3034PBF that most folks use is 1.6~2.0mΩ, I've found a few that are half that, but they aren't cheap!)
I know most of the math I've seen for cooking MOSFETs uses 2.5W as a safe limit, which is about 39.5A - with a heatsink or parallel it should be fine, provided the Vdrop isn't too much
As far as paralleling PPTC fuses, it'll halve the resistance of each, so more from a Vdrop standpoint is better, but you get into space and cost issues, and it seems to be standard practice to limit to 2 per circuit arm
Do a search on Mouser, there are some 30A rated PPTCs

 

[Hell_Vapor]

Your being very very helpful. Does this look like a fuse I could use in parallel? I'll do some more research to make sure it's safe to use and solder and all that good stuff. But is this what your talking about?
http://www.mouser.com/Search/m_Prod...iMZZMsxR%2bBXi4wRULUWu%2b0/KKWjTq%2bLEX0Ijyc=

 

[K3nn0Q]

I was referring more to this: 16R2000SGF

 

[david4500]

Testing of the batteries you mentioned

LG HD2C 20A 2100mAh 18650 Bench Test Results...a 25A/2200mAh battery, better than the HD2