Dual 18650 unregulated box mod mosfet/battery question

[tobyfootball]

hello all

i have recently baught a dual 18650 parallel unregulated box mod with a mosfet and an led in it. At first it worked great still dose but haveing slight issues at moment. first off the question i have is on these is it normal for it to drain the first battery way quicker then the secound? at first it didnt do this at least i dont belive( i just upgraded my charger from an nicore i4 to luc v4) but today i took batterys out to charge and pluged them into charger and the first one was at 3.6V and the 2nd was at 4.0v is this normal?

Secound question/concern the mosfet gets hot sometimes its just warm other times it gets extralmy hot to where u just get close to it it burns you also its one of those ABS houseing and i can feel the heat on the out side of the housing. i bought this on ebay so i dont kow what type of mosfet at this time i will need to take it apart to find that out and i will once i have time and will update. but ive been reading that there needs to be a 15k resistor connected to the mosfet well theres not and no fuses anywhere. dose it need a 15k resistor im just trying to get my hea wrapped around this cause chances are im gonna rebuild it from scratch but at same time would like to know if i baught something that could have problems to bring it to attention of seller. thanks for any help advice thoughts it will be apppreciated and i will update when i get a chance to rip it apart for the mosfet

 

[Mooch]

If you have a parallel mod and one cell is draining that much more than the other, that is not normal. Which mod is it? Are you sure both batteries are in good condition?

Do you have a multimeter? Place just one battery in the left position and carefully measure the voltage across the middle and right legs of the MOSFET. Then move the battery to the right position and remeasure the voltage. Is it the same? If not, there is a problem in the battery holder's contacts or wiring for the side that doesn't show the right voltage.

A MOSFET getting that hot is not good! You definitely need the resistor, it's used to turn the MOSFET solidly off when you release the button. Otherwise the MOSFET can turn off slowly or even never turn all the way off. Sort of like having a leaky faucet. When MOSFETs are turned on only partially they can get extremely hot and easily burn out. This sounds like what us happening to yours. Any value resistor from 1k to 100k (or even lower/higher) can work but 10K-15k seems to be the standard now and will work just fine. But you definitely need a resistor!

Bad battery connection, no resistor, no fuses...not good. You could probably swap in a new MOSFET, add a resistor, and repair or replace the battery holder. But is it worth it? Your call.

 

[tobyfootball]

I didnt think this was normal and yes both batteries are good i just got them a week ago and they are the pair for this mod they stay together charging and vaping and ive even switched the position in the mod.
I do have a multi meter and i will do that when i get a chance.

i didnt think the heat was normal at all just double checking that my gut was on the right track.

I baught it off ebay its title was ABS unregulated box mod with mosfet and led light show.
yeah i dont know what ill do i might eventually just use the housing and rebuild it from scratch so i can add a on/off switch
but thanks for the information it deffinitly shinned light on the subject for me. and in the next day or two i will update on whats up with it.

thanks again

 

[tobyfootball]

so i made up a paint diagram to show how this is wierd. not the best but hey i can only do what i can do. i got out my multi meter and theres n voltage between anything even when i fire the button. im gonna get a new battery for my multimeter tomarrow and try again i will up date with more info

but i dont knw if this is the correct wiring it seems funky to me but i know little to nothing and the led goes from the negative of the atamizer to the lead of the switch that gose to center of mosfet i messed that up

 

[Mooch]

Whoa, as drawn that circuit is not going to work. The left battery is only being used to keep the MOSFET on constantly and the right battery is feeding current to the atomizer through the LED. Are you able to take a draw with that device?

Are you sure that is exactly how all the connections are made? If your multimeter has a resistance setting or a beeper to indicate continuity, you can use that to help test whether your following the connections/wires correctly. It can be pretty tough to do that just visually, usually verrrry crowded in there.

What MOSFET does the device use? Here's a sample circuit for a N-MOSFET.

There are P-MOSFETs too and they need to be wired differently. We need to know which type your device uses.

 

[tobyfootball]

yes im sure that is how it is wired the adhesive that was holding the mosfet in actually gave out so i could take it out, so i could see every wire perfectly. the numbers on the mosfet are
stp30h100ct
7sanf vw
phl ?12
i cant make out the number or letter thats befor the 12. i wrote it exacly how it is on the mosfet

and yes i was abe to use this i actually used this for a good 2 weeks constently with no problem i mean atty and fet would get warm to hot but not like it dose now. and the batterys i belive drained together but i didnt have charger that told me volts just the blinky lights my phone is broke at this time but i should be getting it in mail tomarrow or next day once i receive that i will post images of the box it self and by then i should have better battery for multimeter and ill re try to get voltage. i really appreciate the help

 

[Mooch]

Can't find any info on that MOSFET number. If you're sure it's right then I'm a bit stuck.
I'll take another look at your diagram again.

 

[tobyfootball]

i guess at this point what type of mosfet do u recomend and do u know of a repitible seller i could get it i think im just gonna buy a new mosfet and do it the right way. but again i do really appreciate the help

 

[Mooch]

No problem.
The IRLB3034 is kind of the standard MOSFET that's being used now. But watch out for counterfeits. I use vendors like DigiKey, Mouser, and Newark but I'm ordering lots of stuff. Their shipping costs might add up? Do a search here for vendor recommendations who will have the MOSFET...and fuses too.

Or, better yet...
Check for MOSFET mod build threads as they will have lots of wiring diagrams, parts recommendations, supplier names, etc. i don't have a good thread bookmarked, sorry.

 

[bloodless2010]

There are many different MOSFETs available and the reason being is that they are suited for different circuits, unless you're an electrical engineer I suggest you stick with the recommended MOSFET (which is IRLB3034, stated by Mooch) it is widely used for mods. The problem with the different MOSFETs is that they have different pin configuration (Gate, Drain, Source is used by IRLB3034) I'm not saying this is the problem, but it could be one. The problems you mentioned like overheating will come from the different thresholds from the MOSFET, it probably is too powerful and is wasting loads of energy which is being outputted as heat.

The only datasheet I could find on the MOSFET you stated is here;
http://www.alibaba.com/product-deta...TP3015-STP30150CFP-STP30150CT_1558706891.html

You can checkout the datasheet for the IRLB3034 at
http://www.irf.com/product-info/datasheets/data/irlb3034pbf.pdf

 

[granolaboy]

wow...that is totally wired wrong. mosfet is always on, and all the current is going through the switch.

whoever wired that really doesn't know what they are doing, and probably shouldn't be making mods.

 

[Gummy Bare]

Sounds like one of those china mass made box mods I’ve been seeing online. I've always wondered about those things, and if the Mosfet is really a Mosfet or not. The boxes definitely look cool to use as a DIY enclosure. Slap a new Mosfet on there, take the LED out, and rewire it correctly and you'll be in business.

 

[Gummy Bare]

But watch out for counterfeits. I use vendors like DigiKey, Mouser, and Newark but I'm ordering lots of stuff.

Aww man, now you’re scaring me. I've been collecting parts for some projects for a while now; kinda lost steam but am getting ready to finally make these things. I picked up some Mosfets from DigiKey and some more from eBay. I'm not sure which are which now actually.


Is there any way to spot a fake\counterfeit Mosfet? I'm not even sure who makes Mosfets actually, I kinda thought a bunch of different manufactures made the things.

 

[Mooch]

Aww man, now you’re scaring me. I've been collecting parts for some projects for a while now; kinda lost steam but am getting ready to finally make these things. I picked up some Mosfets from DigiKey and some more from eBay. I'm not sure which are which now actually.


Is there any way to spot a fake\counterfeit Mosfet? I'm not even sure who makes Mosfets actually, I kinda thought a bunch of different manufactures made the things.

You can compare your mosfets to pictures of known authentic ones but that can be hit & miss. You can test them, that's a great way to sort them out.

There are several manufacturers but whichever mosfets you have will only be made by the manufacturing plants for the company your mosfets are supposed to be from. They have some pretty tight control over appearance, labeling, size, surface finish ln the legs/tab, etc. You can get the datasheets from the manufacturer's web sites and go to the last few pages on the datasheet to see how your mosfets should look...not photos, they are dimensional drawings and graphics of where the silkscreening should be. But, because that kind of info is in the datasheet it's the stuff that's used to counterfeit mosfets with. Always best to just buy from the trustworthy distributors or, as you've already bought some, test the mosfets you have and compare the results to known authentic ones.

 

[tobyfootball]

Sounds like one of those china mass made box mods I’ve been seeing online. I've always wondered about those things, and if the Mosfet is really a Mosfet or not. The boxes definitely look cool to use as a DIY enclosure. Slap a new Mosfet on there, take the LED out, and rewire it correctly and you'll be in business.

yeah i bought it cheeply and i really didnt have high hopes for it so im not too disappointed that it crapped out on me cause the box is awsome the perfect size imo. i was actually planning on putting a main switch on it and in when i did that i was gonna rebuild it anyway.

 

[Gummy Bare]

You can compare your mosfets to pictures of known authentic ones but that can be hit & miss. You can test them, that's a great way to sort them out.

There are several manufacturers but whichever mosfets you have will only be made by the manufacturing plants for the company your mosfets are supposed to be from. They have some pretty tight control over appearance, labeling, size, surface finish ln the legs/tab, etc. You can get the datasheets from the manufacturer's web sites and go to the last few pages on the datasheet to see how your mosfets should look...not photos, they are dimensional drawings and graphics of where the silkscreening should be. But, because that kind of info is in the datasheet it's the stuff that's used to counterfeit mosfets with. Always best to just buy from the trustworthy distributors or, as you've already bought some, test the mosfets you have and compare the results to known authentic ones.

Thanks for the info mooch. What kind of equipment does one need to test them? Maybe I can find a youtube video on how to test them.

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[Mooch]

The best way, for vaping purposes, is to pass a lot of current through them and see which get a lot hotter than a known authentic mosfet. You can't use the basic DMM check that most of the online instructions use. That's perfect for checking if the mosfet is dead but not for sorting high resistance ones from lower resistance ones.

Do you have a mosfet box mod you don't need? If you can oull out the wires to the mosfet so you can swap out mosfets and test each one. Though, at a certain point it actually becomes easier to just order new mosfets.

[edit] are there any difference between the ebay and Digikey mosfets? You can safely assume that the digikey ones are genuine. It's the ebay ones that may or may not be a problem.

 

[Gummy Bare]

Thanks again. I'm sure the digikey ones are real like you said, only issue is I got them mixed up with the eBay ones..... ended up putting them in the same bag I believe. I need to do some inventory checks on everything tonight and double check.

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