Box mod build help (not building a box mod, just coil help)

[JayHarris129]

SOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO guys, after ages of wanting a box mod, I finally got one, dual parallel 18650, also got some new VTC4's (got them cheap as well) so what build could I do or rather whats the lowest I can go?

I've been down to .40ohm with my Samsung INR18650-20R battery and that was fine, would this box mod still be the same? Or could I go to .20ohm and still be safe as it's sharing the load between the batteries?

Also gonna be making my own juice soon as well, 100% VG

 

[peps1]

What sort of Box mod is it, If dual parallel 18650's im assuming we are talking a unregulated MOD?

Dose it have a MOSFET, Fuses, what gage wiring?

(without a MOSFET, I wouldn't even go down to 0.4Ω due to the Amp ratting on the vast majority of switches being <20A, and the last thing you want is a switch pole fusing, locking the device on).

 

[JayHarris129]

What sort of Box mod is it, If dual parallel 18650's im assuming we are talking a unregulated MOD?

Dose it have a MOSFET, Fuses, what gage wiring?

(without a MOSFET, I wouldn't even go down to 0.4Ω due to the Amp ratting on the vast majority of switches being <20A, and the last thing you want is a switch pole fusing, locking the device on).

Not like this will help BUT, it's got no MOSFET as far as I know..... Yes it's unregulated

Here's the link to it https://www.fasttech.com/p/2228701

 

[peps1]

Yep, that really not going to be safe for going <.4Ω if there is no MOSFET, that switch looks like the ubiquitous 16mm Anti-Vandal Momentary that is ratted to 3A (if so, making going even sub Ω out of specification).

Will it work, yes, will you get .4Ω yes, will you even be able to go to .2Ω, yes.......But it will fail at that high Amps, maybe no for weeks/months, but when it goes you will have a real bad time!

I'm sure some one on the forum could just whack something like a £2.50 IRLB3034PBF N-channel MOSFET in there for you, making it safe.

Please don't risk going to low on that box!

 

[JayHarris129]

Yep, that really not going to be safe for going <.4Ω if there is no MOSFET, that switch looks like the ubiquitous 16mm Anti-Vandal Momentary that is ratted to 3A (if so, making going even sub Ω out of specification).

Will it work, yes, will you get .4Ω yes, will you even be able to go to .2Ω, yes.......But it will fail at that high Amps, maybe no for weeks/months, but when it goes you will have a real bad time!

I'm sure some one on the forum could just whack something like a £2.50 IRLB3034PBF N-channel MOSFET in there for you, making it safe.

Please don't risk going to low on that box!

With that MOSFET in what would be the gains of it? and how low would I go with it fitted? I can get a new button which is rated higher than that.... I don't mind..... Just wanted a box mod....

 

[peps1]

Just found this video that should help explain things a little better then I can!

https://www.youtube.com/watch?v=Kby8E1cgYl8

With that MOSFET in what would be the gains of it? and how low would I go with it fitted? I can get a new button which is rated higher than that.... I don't mind..... Just wanted a box mod....

They just don't make buttons that can take that many Amps (and fit in a box MOD).

Having a MOSFET fitted means your switch is not taking the load any-more, the MOSFET is, and the right MOSFET will be happy up to 300+ Amps, unlike 20Amps from the best switch possible.

I really couldn't say how low you could go on THAT Box even with a MOSFET, that would be totally irresponsible of me not having seen what sort of wire and fitting are like.

Edit to add:

If you changed to switch to a 20Amp switch, the maths would be:

0.4Ω coil @ 4.2V (max charge of the 18650) = 10.5 Amps
0.3Ω coil @ 4.2V (max charge of the 18650) = 14 Amp
0.2Ω coil @ 4.2V (max charge of the 18650) = 21 Amp
0.1Ω coil @ 4.2V (max charge of the 18650) = 42 Amp
(but this also assumes every other part in the box can take 20Amp too, and that very well may not be the case).

 

[JayHarris129]

Just found this video that should help explain things a little better then I can!

https://www.youtube.com/watch?v=Kby8E1cgYl8



They just don't make buttons that can take that many Amps (and fit in a box MOD).

Having a MOSFET fitted means your switch is not taking the load any-more, the MOSFET is, and the right MOSFET will be happy up to 300+ Amps, unlike 20Amps from the best switch possible.

I really couldn't say how low you could go on THAT Box even with a MOSFET, that would be totally irresponsible of me not having seen what sort of wire and fitting are like.

Edit to add:

If you changed to switch to a 20Amp switch, the maths would be:

0.4Ω coil @ 4.2V (max charge of the 18650) = 10.5 Amps
0.3Ω coil @ 4.2V (max charge of the 18650) = 14 Amp
0.2Ω coil @ 4.2V (max charge of the 18650) = 21 Amp
0.1Ω coil @ 4.2V (max charge of the 18650) = 42 Amp
(but this also assumes every other part in the box can take 20Amp too, and that very well may not be the case).

I just asked my friend and he said he's gonna sort it for me, fitting a MOSFET, 15k Resistor, rewiring it (with better gauge wire) and also making it a series for me as well, not bad for £20 I'd say, what you think?

 

[peps1]

I just asked my friend and he said he's gonna sort it for me, fitting a MOSFET, 15k Resistor, rewiring it (with better gauge wire) and also making it a series for me as well, not bad for £20 I'd say, what you think?

Think £20 is a bloody bargain for all that work!

With having it in series @ 8.4V, maybe start at .6Ω and see if you want to go down to the .3Ω mark as that's going to be 235Watts of cloud chucking power!

Also find out what your batteries are safe down to, as .28Ω is probably going to be the safety limit.

Edit to Add:

Yep VTC4 have a Max Continuous Discharging Current of 30A, so your MAX is:

.28Ω @ 8.4V = 30Amp (series) 252 Watts
.14Ω @ 4.2V = 30Amp (parallel) 126 Watts

 

[JayHarris129]

Think £20 is a bloody bargain for all that work!

With having it in series @ 8.4V, maybe start at .6Ω and see if you want to go down to the .3Ω mark as that's going to be 235Watts of cloud chucking power!

Also find out what your batteries are safe down to, as .28Ω is probably going to be the safety limit.

I got a set of VTC4's coming :-)