Help! Having problem with Mosfet/Charger

[Tubbyengineer]

Ok so this is only based on my own tests and using these FET's in my builds but I would say that either FET is good for builds unlikely to be used for more than 50W vaping, assuming a good battery source(2x18650, lipo packs etc).

If more than 50W vaping is desired I would use-

IRF3711pbf for LIPO builds/battery sources with low voltage drop

IRLB8748pbf for standard battery builds (18650 etc) with higher voltage drop.




I hope that makes it clearer, the problem is that it all depends on the voltage drop on the batteries under load.

You can more than likely squeeze an extra 30% current out of these by slapping a heatsink on them, wouldnt have to be huge but based on 5 to 10 second draws with 30 seconds between draws a heatsink would do a lot to keep things from getting too warm, frankly on a dual parralel build with IMR's a small heat sink would extend the mosfets current capacity beyond the batteries limits - you'd need a triple to ruin the mosfet then...

 

[RicModMaker]

You can more than likely squeeze an extra 30% current out of these by slapping a heatsink on them, wouldnt have to be huge but based on 5 to 10 second draws with 30 seconds between draws a heatsink would do a lot to keep things from getting too warm, frankly on a dual parralel build with IMR's a small heat sink would extend the mosfets current capacity beyond the batteries limits - you'd need a triple to ruin the mosfet then...

Tubbys knowledge to the rescue ;-)
This will probably sound stupid but by simply attaching a lump of brass to the mosfet, would this be an effective heatsink?

 

[Tubbyengineer]

Tubbys knowledge to the rescue ;-)
This will probably sound stupid but by simply attaching a lump of brass to the mosfet, would this be an effective heatsink?

A lump of brass would work but your better off with proper heat sinks, you can pick them up from about 50p for a simple pressed metal one that would add 5 or 10% and about £2 for one that would out rate the batteries. Dont forget a mosfet wont mind firing at 60 or 70 centigrade for 20 or 30 seconds as long as it gets a cool down period, heatsinks are designed to absorb heat quickly and then radiate it away. If you want to make your own use brass sheet and cut it into fins to radiate heat away quickly, but dont forget the metal tab on most mosfets is part of the circuit (Usually drain or source depending on maker) so either use insulating sheet (Pennies from Farnell or RS) or make sure nothing can touch the heatsink.

 

[RicModMaker]

A lump of brass would work but your better off with proper heat sinks, you can pick them up from about 50p for a simple pressed metal one that would add 5 or 10% and about £2 for one that would out rate the batteries. Dont forget a mosfet wont mind firing at 60 or 70 centigrade for 20 or 30 seconds as long as it gets a cool down period, heatsinks are designed to absorb heat quickly and then radiate it away. If you want to make your own use brass sheet and cut it into fins to radiate heat away quickly, but dont forget the metal tab on most mosfets is part of the circuit (Usually drain or source depending on maker) so either use insulating sheet (Pennies from Farnell or RS) or make sure nothing can touch the heatsink.

A knowledgeable and well explained reply. Thank you kind sir. :-)

 

[BaDaBooM]

Tubbys knowledge to the rescue ;-)
This will probably sound stupid but by simply attaching a lump of brass to the mosfet, would this be an effective heatsink?

Aluminum would be better because it dissipates heat much better than brass, now you have a mill you can make one If you want to go all out it would be batter to have a polished copper plate between the heat-sink and the mofest, copper conducts heats and aluminum dissipates it, in other words the copper will suck up the heat and the aluminum will get rid of it.

 

[RicModMaker]

A lump of brass would work but your better off with proper heat sinks, you can pick them up from about 50p for a simple pressed metal one that would add 5 or 10% and about £2 for one that would out rate the batteries. Dont forget a mosfet wont mind firing at 60 or 70 centigrade for 20 or 30 seconds as long as it gets a cool down period, heatsinks are designed to absorb heat quickly and then radiate it away. If you want to make your own use brass sheet and cut it into fins to radiate heat away quickly, but dont forget the metal tab on most mosfets is part of the circuit (Usually drain or source depending on maker) so either use insulating sheet (Pennies from Farnell or RS) or make sure nothing can touch the heatsink.

At last. Something to use my new mill on. I think I'll make some ;-)

 

[Tubbyengineer]

Now Now, move along please, stop milling around...

 

[RicModMaker]

Now Now, move along please, stop milling around...

That's a cutting remark!

 

[Tubbyengineer]

Ooohh, sharp reply...

 

[fasteddie600]

Cheers tubby, informative advice thanks!

I would love to heatsink in my MOD's especially as that could potentially look awesome, unfortunately layout has meant it easier to put an extra FET in and reduce heat that way. Which ever way works I guess.