Unregulated dual 18650 box mod (series)

[Jake R.]

Hello I'm new to the forums, but have been vaping for a while now. I have built mods before, for example a massive hammer of Thor, and a dual 18650 box mod wired parallel. My question is, is a mosfet really required? On my other mod I have a 3 amp switch wired up to the negatives and it works just fine. Do amp loads not carry thru negatives? Am I able to eliminate the mosfet?

 

[freemind]

No mod building expert, but will be jumping in soon...

From all I have gathered:
A mofset is used because your switch can't handle the amps that are run through it. Your build (coil) might be running 20 amps of draw, but your switch Is rated for 3. Meaning, quickly your switch will fail or maybe melt together.

 

[Jake R.]

Yes I know that's what it's used for but I've had builds down to .3 ohms which would pull roughly 12 amps on a freshly charged battery. The switch in my other one is just a cheap radio shack one rated at 3 amps. I've used the box all day and works great. I just don't get why the switch hasn't blown. I'm drawing almost 12 amps. I'm no expert in electricity haha.

 

[BoomStick]

Those switches are rated for 3 amps at 120 volts ac. Different animal.

 

[Jake R.]

Those switches are rated for 3 amps at 120 volts ac. Different animal.

True but are you able to explain how it hasn't blown by now being soldered to the negative wires?

 

[BoomStick]

Switch ratings are based on the amount of current they can break. There is no good way to convert the ratings of a switch designed for a/c to a d/c equivilant. If you want to be sure you're using the right switch for a d/c application, get a switch that has a d/c rating. As to your question, the reason it hasn't failed probably has to do with the low voltage that's being used.

 

[Jake R.]

Switch ratings are based on the amount of current they can break. There is no good way to convert the ratings of a switch designed for a/c to a d/c equivilant. If you want to be sure you're using the right switch for a d/c application, get a switch that has a d/c rating. As to your question, the reason it hasn't failed probably has to do with the low voltage that's being used.[/QUOT

Ah ok it makes sense now. I'll have to look for a d/c switch for the new mod. Thank you!

 

[BoomStick]

Finding a switch with a dc rating can be difficult and proper high current switches can be expensive. That's why most use a MOSFET. The fet handles the current so you can use just about whatever switch you want. Most people find the 3 amp switches work fine for 4 volt boxes with no fet. I haven't seen anything about what folks are doing for 8 volt series boxes.

 

[Jake R.]

Oh ok. I have tried wiring mosfets in with my mod. I tried 2 different ones. But I think I might have over heated them? Is their a way you can tell?