Purpose of Multiple Parallel MOSFETs in Circuit

[Kantanshi]

I've gotten into the "vape" community and many people are going DIY. I've been checking schematics and it appears there are 2 designs they are using. I'm an amateur with electronics and need some help understanding something. I know the purpose of using a MOFSET in the circuit, they seem to be using the IRLB3034PBF. Most are using 1 in their design. Some people, however, are stacking 2 of them by soldering the leads together. I've never seen this done so there's 2 things I wonder about. First is if this actually helps at all. They say it is to allow higher current. Second is if this actually helps or is it pointless? Also, I've been trying to research MOFSETs and learned about double gates. Would this be a better option and if so, what P/N should I use as a substitute?

 

[Audioguru]

What is a "510"?
Are the battery cells 18650 3.7V lithium, 1.2V Ni-MH or 1.5V Alkaline??

It is unlikely that you will find Mosfets that are identical. Usually one will conduct more current than the other one so they will not share the current equally, but they will allow higher current if the load needs it and if the battery can supply it.

 

[D.A.(Tony)Stewart]

It also looks like a squid firing circuit for an incendiary device.

Many MOSFETs now are designed with PTC characteristics and are preferred for gang operation in lowering the RdsOn to reduce wasted energy and vaporize fluids. Digikey has about 10k different MOSFETs so pick one with an RdsOn <5% of the heater resistance.

 

[Kantanshi]

What is a "510"?
Are the battery cells 18650 3.7V lithium, 1.2V Ni-MH or 1.5V Alkaline??

The 510 is a threaded connector. They are using primarily 18650 batteries.

 

[chemelec]

Considering This Mosfet has a VERY LOW On Resistance "1.7 mil-Ohms" and its rated at "195 Amps", I don't see any advantage in paralleling 2 of them.
More Important to use leads with Big Wires and Short as Possible.

 

[PatrickPribyl]

I would expect there will be a measurable difference when the batteries are marginal, so that there is less voltage available to turn on the transistor. Figure 1 in the spec sheet indicates that at 2.5V (e.g. old resistive batteries mostly discharged) the current through one transistor would be limited to 4-5A.

 

[Kantanshi]

One thing I want to add. I don't know where the title of my post came from. I had titled it "MOSFET advice needed please". I already know the purpose of the MOSFET....

But yes, when I am able to afford the build, I know basic electronics assembly techniques. I've also been rated for mil spec soldering in the past. I watch videos of these guys putting their vaping mod boxes together and cringe at the excessively long wiring, the solder blobs... and then saying how good their work is. It scares me to think that there's people out there following these "instruction" videos. One girl even commented something like "I did everything you said in the video. Why are my wires melting?"

 

[FvM]

One thing I want to add. I don't know where the title of my post came from. I had titled it "MOSFET advice needed please". I already know the purpose of the MOSFET....

Can tell you about it. The title was changed by a moderator because ""MOSFET advice needed please" is pretty meaningless.

It's good that you already know the purpose of MOSFET. It would be better if you had been able to chose a more specific title....

 

[Kantanshi]

Can tell you about it. The title was changed by a moderator because ""MOSFET advice needed please" is pretty meaningless.

It's good that you already know the purpose of MOSFET. It would be better if you had been able to chose a more specific title....

The only issue I have with the title assigned by someone else is that it currently looks more like someone is posting facts about it, not asking a question. If it can still be changed, how about "Parallel MOSFET advice needed please"

 

[bigdogguru]

The only issue I have with the title assigned by someone else is that it currently looks more like someone is posting facts about it, not asking a question. If it can still be changed, how about "Parallel MOSFET advice needed please"

The title of a thread should be primarily composed of keywords specifically related to the question, query or advice sought as expressed in the content of the thread, not its title, this facilitates members scanning thread titles to determine if they can participate in a topic with which they are familiar and also facilitates other members whom search for answers to similar questions or queries.

Purely gratuitous words like please and help should NEVER appear in a thread title and should be reserved for the content of your thread.

All threads in this and most other sections of this forum are questions, queries or seeking specific advice, which are in need of an answer or advice, therefore words like needed are superfluous and should typically not appear in a thread title.

In short, the content of the thread is where the specific question, query or advice sought should be posed, not the thread title.

The thread title has been changed to the following, "Purpose of Multiple Parallel MOSFETs in Circuit" which now is composed of a sufficient number of keywords to indicate the overall topic of the thread.

In the future, please select your thread titles more carefully according to the above guidelines, doing so will increase the number and quality of the replies to your thread.

BigDog

 

[Audioguru]

I had to look up Vape and Vaping in Google. This electronic device powers an e-cigarette heater so the e-cigarette produces its VAPor, cough cough. Most e-cigarettes DO NOT use two 18650 battery cells in parallel, and some of the single battery cells are much smaller and produce less current than an 18650.